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1 | <?xml version='1.0'?> | |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [ | |
4 | <!ENTITY fedora_latest_version "30"> | |
5 | <!ENTITY fedora_cloud_release "1.2"> | |
6 | ]> | |
7 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> | |
8 | ||
9 | <refentry id="systemd-nspawn" | |
10 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
11 | ||
12 | <refentryinfo> | |
13 | <title>systemd-nspawn</title> | |
14 | <productname>systemd</productname> | |
15 | </refentryinfo> | |
16 | ||
17 | <refmeta> | |
18 | <refentrytitle>systemd-nspawn</refentrytitle> | |
19 | <manvolnum>1</manvolnum> | |
20 | </refmeta> | |
21 | ||
22 | <refnamediv> | |
23 | <refname>systemd-nspawn</refname> | |
24 | <refpurpose>Spawn a command or OS in a light-weight container</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <cmdsynopsis> | |
29 | <command>systemd-nspawn</command> | |
30 | <arg choice="opt" rep="repeat">OPTIONS</arg> | |
31 | <arg choice="opt"><replaceable>COMMAND</replaceable> | |
32 | <arg choice="opt" rep="repeat">ARGS</arg> | |
33 | </arg> | |
34 | </cmdsynopsis> | |
35 | <cmdsynopsis> | |
36 | <command>systemd-nspawn</command> | |
37 | <arg choice="plain">--boot</arg> | |
38 | <arg choice="opt" rep="repeat">OPTIONS</arg> | |
39 | <arg choice="opt" rep="repeat">ARGS</arg> | |
40 | </cmdsynopsis> | |
41 | </refsynopsisdiv> | |
42 | ||
43 | <refsect1> | |
44 | <title>Description</title> | |
45 | ||
46 | <para><command>systemd-nspawn</command> may be used to run a command or OS in a light-weight namespace | |
47 | container. In many ways it is similar to <citerefentry | |
48 | project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>, but more powerful | |
49 | since it fully virtualizes the file system hierarchy, as well as the process tree, the various IPC subsystems and | |
50 | the host and domain name.</para> | |
51 | ||
52 | <para><command>systemd-nspawn</command> may be invoked on any directory tree containing an operating system tree, | |
53 | using the <option>--directory=</option> command line option. By using the <option>--machine=</option> option an OS | |
54 | tree is automatically searched for in a couple of locations, most importantly in | |
55 | <filename>/var/lib/machines</filename>, the suggested directory to place OS container images installed on the | |
56 | system.</para> | |
57 | ||
58 | <para>In contrast to <citerefentry | |
59 | project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command> | |
60 | may be used to boot full Linux-based operating systems in a container.</para> | |
61 | ||
62 | <para><command>systemd-nspawn</command> limits access to various kernel interfaces in the container to read-only, | |
63 | such as <filename>/sys</filename>, <filename>/proc/sys</filename> or <filename>/sys/fs/selinux</filename>. The | |
64 | host's network interfaces and the system clock may not be changed from within the container. Device nodes may not | |
65 | be created. The host system cannot be rebooted and kernel modules may not be loaded from within the | |
66 | container.</para> | |
67 | ||
68 | <para>Use a tool like <citerefentry | |
69 | project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry | |
70 | project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or | |
71 | <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry> to | |
72 | set up an OS directory tree suitable as file system hierarchy for <command>systemd-nspawn</command> containers. See | |
73 | the Examples section below for details on suitable invocation of these commands.</para> | |
74 | ||
75 | <para>As a safety check <command>systemd-nspawn</command> will verify the existence of | |
76 | <filename>/usr/lib/os-release</filename> or <filename>/etc/os-release</filename> in the container tree before | |
77 | starting the container (see | |
78 | <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It might be | |
79 | necessary to add this file to the container tree manually if the OS of the container is too old to contain this | |
80 | file out-of-the-box.</para> | |
81 | ||
82 | <para><command>systemd-nspawn</command> may be invoked directly from the interactive command line or run as system | |
83 | service in the background. In this mode each container instance runs as its own service instance; a default | |
84 | template unit file <filename>systemd-nspawn@.service</filename> is provided to make this easy, taking the container | |
85 | name as instance identifier. Note that different default options apply when <command>systemd-nspawn</command> is | |
86 | invoked by the template unit file than interactively on the command line. Most importantly the template unit file | |
87 | makes use of the <option>--boot</option> which is not the default in case <command>systemd-nspawn</command> is | |
88 | invoked from the interactive command line. Further differences with the defaults are documented along with the | |
89 | various supported options below.</para> | |
90 | ||
91 | <para>The <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool may | |
92 | be used to execute a number of operations on containers. In particular it provides easy-to-use commands to run | |
93 | containers as system services using the <filename>systemd-nspawn@.service</filename> template unit | |
94 | file.</para> | |
95 | ||
96 | <para>Along with each container a settings file with the <filename>.nspawn</filename> suffix may exist, containing | |
97 | additional settings to apply when running the container. See | |
98 | <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry> for | |
99 | details. Settings files override the default options used by the <filename>systemd-nspawn@.service</filename> | |
100 | template unit file, making it usually unnecessary to alter this template file directly.</para> | |
101 | ||
102 | <para>Note that <command>systemd-nspawn</command> will mount file systems private to the container to | |
103 | <filename>/dev</filename>, <filename>/run</filename> and similar. These will not be visible outside of the | |
104 | container, and their contents will be lost when the container exits.</para> | |
105 | ||
106 | <para>Note that running two <command>systemd-nspawn</command> containers from the same directory tree will not make | |
107 | processes in them see each other. The PID namespace separation of the two containers is complete and the containers | |
108 | will share very few runtime objects except for the underlying file system. Use | |
109 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s | |
110 | <command>login</command> or <command>shell</command> commands to request an additional login session in a running | |
111 | container.</para> | |
112 | ||
113 | <para><command>systemd-nspawn</command> implements the <ulink | |
114 | url="https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container Interface</ulink> | |
115 | specification.</para> | |
116 | ||
117 | <para>While running, containers invoked with <command>systemd-nspawn</command> are registered with the | |
118 | <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> service that | |
119 | keeps track of running containers, and provides programming interfaces to interact with them.</para> | |
120 | </refsect1> | |
121 | ||
122 | <refsect1> | |
123 | <title>Options</title> | |
124 | ||
125 | <para>If option <option>-b</option> is specified, the arguments | |
126 | are used as arguments for the init program. Otherwise, | |
127 | <replaceable>COMMAND</replaceable> specifies the program to launch | |
128 | in the container, and the remaining arguments are used as | |
129 | arguments for this program. If <option>--boot</option> is not used and | |
130 | no arguments are specified, a shell is launched in the | |
131 | container.</para> | |
132 | ||
133 | <para>The following options are understood:</para> | |
134 | ||
135 | <variablelist> | |
136 | ||
137 | <varlistentry> | |
138 | <term><option>-q</option></term> | |
139 | <term><option>--quiet</option></term> | |
140 | ||
141 | <listitem><para>Turns off any status output by the tool | |
142 | itself. When this switch is used, the only output from nspawn | |
143 | will be the console output of the container OS | |
144 | itself.</para></listitem> | |
145 | </varlistentry> | |
146 | ||
147 | <varlistentry> | |
148 | <term><option>--settings=</option><replaceable>MODE</replaceable></term> | |
149 | ||
150 | <listitem><para>Controls whether | |
151 | <command>systemd-nspawn</command> shall search for and use | |
152 | additional per-container settings from | |
153 | <filename>.nspawn</filename> files. Takes a boolean or the | |
154 | special values <option>override</option> or | |
155 | <option>trusted</option>.</para> | |
156 | ||
157 | <para>If enabled (the default), a settings file named after the | |
158 | machine (as specified with the <option>--machine=</option> | |
159 | setting, or derived from the directory or image file name) | |
160 | with the suffix <filename>.nspawn</filename> is searched in | |
161 | <filename>/etc/systemd/nspawn/</filename> and | |
162 | <filename>/run/systemd/nspawn/</filename>. If it is found | |
163 | there, its settings are read and used. If it is not found | |
164 | there, it is subsequently searched in the same directory as the | |
165 | image file or in the immediate parent of the root directory of | |
166 | the container. In this case, if the file is found, its settings | |
167 | will be also read and used, but potentially unsafe settings | |
168 | are ignored. Note that in both these cases, settings on the | |
169 | command line take precedence over the corresponding settings | |
170 | from loaded <filename>.nspawn</filename> files, if both are | |
171 | specified. Unsafe settings are considered all settings that | |
172 | elevate the container's privileges or grant access to | |
173 | additional resources such as files or directories of the | |
174 | host. For details about the format and contents of | |
175 | <filename>.nspawn</filename> files, consult | |
176 | <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> | |
177 | ||
178 | <para>If this option is set to <option>override</option>, the | |
179 | file is searched, read and used the same way, however, the order of | |
180 | precedence is reversed: settings read from the | |
181 | <filename>.nspawn</filename> file will take precedence over | |
182 | the corresponding command line options, if both are | |
183 | specified.</para> | |
184 | ||
185 | <para>If this option is set to <option>trusted</option>, the | |
186 | file is searched, read and used the same way, but regardless | |
187 | of being found in <filename>/etc/systemd/nspawn/</filename>, | |
188 | <filename>/run/systemd/nspawn/</filename> or next to the image | |
189 | file or container root directory, all settings will take | |
190 | effect, however, command line arguments still take precedence | |
191 | over corresponding settings.</para> | |
192 | ||
193 | <para>If disabled, no <filename>.nspawn</filename> file is read | |
194 | and no settings except the ones on the command line are in | |
195 | effect.</para></listitem> | |
196 | </varlistentry> | |
197 | ||
198 | </variablelist> | |
199 | ||
200 | <refsect2> | |
201 | <title>Image Options</title> | |
202 | ||
203 | <variablelist> | |
204 | ||
205 | <varlistentry> | |
206 | <term><option>-D</option></term> | |
207 | <term><option>--directory=</option></term> | |
208 | ||
209 | <listitem><para>Directory to use as file system root for the | |
210 | container.</para> | |
211 | ||
212 | <para>If neither <option>--directory=</option>, nor | |
213 | <option>--image=</option> is specified the directory is | |
214 | determined by searching for a directory named the same as the | |
215 | machine name specified with <option>--machine=</option>. See | |
216 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
217 | section "Files and Directories" for the precise search path.</para> | |
218 | ||
219 | <para>If neither <option>--directory=</option>, | |
220 | <option>--image=</option>, nor <option>--machine=</option> | |
221 | are specified, the current directory will | |
222 | be used. May not be specified together with | |
223 | <option>--image=</option>.</para></listitem> | |
224 | </varlistentry> | |
225 | ||
226 | <varlistentry> | |
227 | <term><option>--template=</option></term> | |
228 | ||
229 | <listitem><para>Directory or <literal>btrfs</literal> subvolume to use as template for the | |
230 | container's root directory. If this is specified and the container's root directory (as configured by | |
231 | <option>--directory=</option>) does not yet exist it is created as <literal>btrfs</literal> snapshot | |
232 | (if supported) or plain directory (otherwise) and populated from this template tree. Ideally, the | |
233 | specified template path refers to the root of a <literal>btrfs</literal> subvolume, in which case a | |
234 | simple copy-on-write snapshot is taken, and populating the root directory is instant. If the | |
235 | specified template path does not refer to the root of a <literal>btrfs</literal> subvolume (or not | |
236 | even to a <literal>btrfs</literal> file system at all), the tree is copied (though possibly in a | |
237 | 'reflink' copy-on-write scheme — if the file system supports that), which can be substantially more | |
238 | time-consuming. Note that the snapshot taken is of the specified directory or subvolume, including | |
239 | all subdirectories and subvolumes below it, but excluding any sub-mounts. May not be specified | |
240 | together with <option>--image=</option> or <option>--ephemeral</option>.</para> | |
241 | ||
242 | <para>Note that this switch leaves host name, machine ID and | |
243 | all other settings that could identify the instance | |
244 | unmodified.</para></listitem> | |
245 | </varlistentry> | |
246 | ||
247 | <varlistentry> | |
248 | <term><option>-x</option></term> | |
249 | <term><option>--ephemeral</option></term> | |
250 | ||
251 | <listitem><para>If specified, the container is run with a temporary snapshot of its file system that is removed | |
252 | immediately when the container terminates. May not be specified together with | |
253 | <option>--template=</option>.</para> | |
254 | <para>Note that this switch leaves host name, machine ID and all other settings that could identify | |
255 | the instance unmodified. Please note that — as with <option>--template=</option> — taking the | |
256 | temporary snapshot is more efficient on file systems that support subvolume snapshots or 'reflinks' | |
257 | natively (<literal>btrfs</literal> or new <literal>xfs</literal>) than on more traditional file | |
258 | systems that do not (<literal>ext4</literal>). Note that the snapshot taken is of the specified | |
259 | directory or subvolume, including all subdirectories and subvolumes below it, but excluding any | |
260 | sub-mounts.</para> | |
261 | ||
262 | <para>With this option no modifications of the container image are retained. Use | |
263 | <option>--volatile=</option> (described below) for other mechanisms to restrict persistency of | |
264 | container images during runtime.</para> | |
265 | </listitem> | |
266 | </varlistentry> | |
267 | ||
268 | <varlistentry> | |
269 | <term><option>-i</option></term> | |
270 | <term><option>--image=</option></term> | |
271 | ||
272 | <listitem><para>Disk image to mount the root directory for the | |
273 | container from. Takes a path to a regular file or to a block | |
274 | device node. The file or block device must contain | |
275 | either:</para> | |
276 | ||
277 | <itemizedlist> | |
278 | <listitem><para>An MBR partition table with a single | |
279 | partition of type 0x83 that is marked | |
280 | bootable.</para></listitem> | |
281 | ||
282 | <listitem><para>A GUID partition table (GPT) with a single | |
283 | partition of type | |
284 | 0fc63daf-8483-4772-8e79-3d69d8477de4.</para></listitem> | |
285 | ||
286 | <listitem><para>A GUID partition table (GPT) with a marked | |
287 | root partition which is mounted as the root directory of the | |
288 | container. Optionally, GPT images may contain a home and/or | |
289 | a server data partition which are mounted to the appropriate | |
290 | places in the container. All these partitions must be | |
291 | identified by the partition types defined by the <ulink | |
292 | url="https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable | |
293 | Partitions Specification</ulink>.</para></listitem> | |
294 | ||
295 | <listitem><para>No partition table, and a single file system spanning the whole image.</para></listitem> | |
296 | </itemizedlist> | |
297 | ||
298 | <para>On GPT images, if an EFI System Partition (ESP) is discovered, it is automatically mounted to | |
299 | <filename>/efi</filename> (or <filename>/boot</filename> as fallback) in case a directory by this name exists | |
300 | and is empty.</para> | |
301 | ||
302 | <para>Partitions encrypted with LUKS are automatically decrypted. Also, on GPT images dm-verity data integrity | |
303 | hash partitions are set up if the root hash for them is specified using the <option>--root-hash=</option> | |
304 | option.</para> | |
305 | ||
306 | <para>Any other partitions, such as foreign partitions or swap partitions are not mounted. May not be specified | |
307 | together with <option>--directory=</option>, <option>--template=</option>.</para></listitem> | |
308 | </varlistentry> | |
309 | ||
310 | <varlistentry> | |
311 | <term><option>--oci-bundle=</option></term> | |
312 | ||
313 | <listitem><para>Takes the path to an OCI runtime bundle to invoke, as specified in the <ulink | |
314 | url="https://github.com/opencontainers/runtime-spec/blob/master/spec.md">OCI Runtime Specification</ulink>. In | |
315 | this case no <filename>.nspawn</filename> file is loaded, and the root directory and various settings are read | |
316 | from the OCI runtime JSON data (but data passed on the command line takes precedence).</para></listitem> | |
317 | </varlistentry> | |
318 | ||
319 | <varlistentry> | |
320 | <term><option>--read-only</option></term> | |
321 | ||
322 | <listitem><para>Mount the container's root file system (and any other file systems container in the container | |
323 | image) read-only. This has no effect on additional mounts made with <option>--bind=</option>, | |
324 | <option>--tmpfs=</option> and similar options. This mode is implied if the container image file or directory is | |
325 | marked read-only itself. It is also implied if <option>--volatile=</option> is used. In this case the container | |
326 | image on disk is strictly read-only, while changes are permitted but kept non-persistently in memory only. For | |
327 | further details, see below.</para></listitem> | |
328 | </varlistentry> | |
329 | ||
330 | <varlistentry> | |
331 | <term><option>--volatile</option></term> | |
332 | <term><option>--volatile=</option><replaceable>MODE</replaceable></term> | |
333 | ||
334 | <listitem><para>Boots the container in volatile mode. When no mode parameter is passed or when mode is | |
335 | specified as <option>yes</option>, full volatile mode is enabled. This means the root directory is mounted as a | |
336 | mostly unpopulated <literal>tmpfs</literal> instance, and <filename>/usr/</filename> from the OS tree is | |
337 | mounted into it in read-only mode (the system thus starts up with read-only OS image, but pristine state and | |
338 | configuration, any changes are lost on shutdown). When the mode parameter is specified as | |
339 | <option>state</option>, the OS tree is mounted read-only, but <filename>/var/</filename> is mounted as a | |
340 | writable <literal>tmpfs</literal> instance into it (the system thus starts up with read-only OS resources and | |
341 | configuration, but pristine state, and any changes to the latter are lost on shutdown). When the mode parameter | |
342 | is specified as <option>overlay</option> the read-only root file system is combined with a writable | |
343 | <filename>tmpfs</filename> instance through <literal>overlayfs</literal>, so that it appears at it normally | |
344 | would, but any changes are applied to the temporary file system only and lost when the container is | |
345 | terminated. When the mode parameter is specified as <option>no</option> (the default), the whole OS tree is | |
346 | made available writable (unless <option>--read-only</option> is specified, see above).</para> | |
347 | ||
348 | <para>Note that if one of the volatile modes is chosen, its effect is limited to the root file system (or | |
349 | <filename>/var/</filename> in case of <option>state</option>), and any other mounts placed in the hierarchy are | |
350 | unaffected — regardless if they are established automatically (e.g. the EFI system partition that might be | |
351 | mounted to <filename>/efi/</filename> or <filename>/boot/</filename>) or explicitly (e.g. through an additional | |
352 | command line option such as <option>--bind=</option>, see below). This means, even if | |
353 | <option>--volatile=overlay</option> is used changes to <filename>/efi/</filename> or | |
354 | <filename>/boot/</filename> are prohibited in case such a partition exists in the container image operated on, | |
355 | and even if <option>--volatile=state</option> is used the hypothetical file <filename>/etc/foobar</filename> is | |
356 | potentially writable if <option>--bind=/etc/foobar</option> if used to mount it from outside the read-only | |
357 | container <filename>/etc</filename> directory.</para> | |
358 | ||
359 | <para>The <option>--ephemeral</option> option is closely related to this setting, and provides similar | |
360 | behaviour by making a temporary, ephemeral copy of the whole OS image and executing that. For further details, | |
361 | see above.</para> | |
362 | ||
363 | <para>The <option>--tmpfs=</option> and <option>--overlay=</option> options provide similar functionality, but | |
364 | for specific sub-directories of the OS image only. For details, see below.</para> | |
365 | ||
366 | <para>This option provides similar functionality for containers as the <literal>systemd.volatile=</literal> | |
367 | kernel command line switch provides for host systems. See | |
368 | <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry> for | |
369 | details.</para> | |
370 | ||
371 | <para>Note that setting this option to <option>yes</option> or <option>state</option> will only work | |
372 | correctly with operating systems in the container that can boot up with only | |
373 | <filename>/usr/</filename> mounted, and are able to automatically populate <filename>/var/</filename> | |
374 | (and <filename>/etc/</filename> in case of <literal>--volatile=yes</literal>). Specifically, this | |
375 | means that operating systems that follow the historic split of <filename>/bin/</filename> and | |
376 | <filename>/lib/</filename> (and related directories) from <filename>/usr/</filename> (i.e. where the | |
377 | former are not symlinks into the latter) are not supported by <literal>--volatile=yes</literal> as | |
378 | container payload. The <option>overlay</option> option does not require any particular preparations | |
379 | in the OS, but do note that <literal>overlayfs</literal> behaviour differs from regular file systems | |
380 | in a number of ways, and hence compatibility is limited.</para></listitem> | |
381 | </varlistentry> | |
382 | ||
383 | <varlistentry> | |
384 | <term><option>--root-hash=</option></term> | |
385 | ||
386 | <listitem><para>Takes a data integrity (dm-verity) root hash specified in hexadecimal. This option enables data | |
387 | integrity checks using dm-verity, if the used image contains the appropriate integrity data (see above). The | |
388 | specified hash must match the root hash of integrity data, and is usually at least 256 bits (and hence 64 | |
389 | formatted hexadecimal characters) long (in case of SHA256 for example). If this option is not specified, but | |
390 | the image file carries the <literal>user.verity.roothash</literal> extended file attribute (see <citerefentry | |
391 | project='man-pages'><refentrytitle>xattr</refentrytitle><manvolnum>7</manvolnum></citerefentry>), then the root | |
392 | hash is read from it, also as formatted hexadecimal characters. If the extended file attribute is not found (or | |
393 | is not supported by the underlying file system), but a file with the <filename>.roothash</filename> suffix is | |
394 | found next to the image file, bearing otherwise the same name, the root hash is read from it and automatically | |
395 | used, also as formatted hexadecimal characters.</para></listitem> | |
396 | </varlistentry> | |
397 | ||
398 | <varlistentry> | |
399 | <term><option>--pivot-root=</option></term> | |
400 | ||
401 | <listitem><para>Pivot the specified directory to <filename>/</filename> inside the container, and either unmount the | |
402 | container's old root, or pivot it to another specified directory. Takes one of: a path argument — in which case the | |
403 | specified path will be pivoted to <filename>/</filename> and the old root will be unmounted; or a colon-separated pair | |
404 | of new root path and pivot destination for the old root. The new root path will be pivoted to <filename>/</filename>, | |
405 | and the old <filename>/</filename> will be pivoted to the other directory. Both paths must be absolute, and are resolved | |
406 | in the container's file system namespace.</para> | |
407 | ||
408 | <para>This is for containers which have several bootable directories in them; for example, several | |
409 | <ulink url="https://ostree.readthedocs.io/en/latest/">OSTree</ulink> deployments. It emulates the behavior of | |
410 | the boot loader and initial RAM disk which normally select which directory to mount as the root and start the | |
411 | container's PID 1 in.</para></listitem> | |
412 | </varlistentry> | |
413 | </variablelist> | |
414 | ||
415 | </refsect2><refsect2> | |
416 | <title>Execution Options</title> | |
417 | ||
418 | <variablelist> | |
419 | <varlistentry> | |
420 | <term><option>-a</option></term> | |
421 | <term><option>--as-pid2</option></term> | |
422 | ||
423 | <listitem><para>Invoke the shell or specified program as process ID (PID) 2 instead of PID 1 (init). By | |
424 | default, if neither this option nor <option>--boot</option> is used, the selected program is run as the process | |
425 | with PID 1, a mode only suitable for programs that are aware of the special semantics that the process with | |
426 | PID 1 has on UNIX. For example, it needs to reap all processes reparented to it, and should implement | |
427 | <command>sysvinit</command> compatible signal handling (specifically: it needs to reboot on SIGINT, reexecute | |
428 | on SIGTERM, reload configuration on SIGHUP, and so on). With <option>--as-pid2</option> a minimal stub init | |
429 | process is run as PID 1 and the selected program is executed as PID 2 (and hence does not need to implement any | |
430 | special semantics). The stub init process will reap processes as necessary and react appropriately to | |
431 | signals. It is recommended to use this mode to invoke arbitrary commands in containers, unless they have been | |
432 | modified to run correctly as PID 1. Or in other words: this switch should be used for pretty much all commands, | |
433 | except when the command refers to an init or shell implementation, as these are generally capable of running | |
434 | correctly as PID 1. This option may not be combined with <option>--boot</option>.</para> | |
435 | </listitem> | |
436 | </varlistentry> | |
437 | ||
438 | <varlistentry> | |
439 | <term><option>-b</option></term> | |
440 | <term><option>--boot</option></term> | |
441 | ||
442 | <listitem><para>Automatically search for an init program and invoke it as PID 1, instead of a shell or a user | |
443 | supplied program. If this option is used, arguments specified on the command line are used as arguments for the | |
444 | init program. This option may not be combined with <option>--as-pid2</option>.</para> | |
445 | ||
446 | <para>The following table explains the different modes of invocation and relationship to | |
447 | <option>--as-pid2</option> (see above):</para> | |
448 | ||
449 | <table> | |
450 | <title>Invocation Mode</title> | |
451 | <tgroup cols='2' align='left' colsep='1' rowsep='1'> | |
452 | <colspec colname="switch" /> | |
453 | <colspec colname="explanation" /> | |
454 | <thead> | |
455 | <row> | |
456 | <entry>Switch</entry> | |
457 | <entry>Explanation</entry> | |
458 | </row> | |
459 | </thead> | |
460 | <tbody> | |
461 | <row> | |
462 | <entry>Neither <option>--as-pid2</option> nor <option>--boot</option> specified</entry> | |
463 | <entry>The passed parameters are interpreted as the command line, which is executed as PID 1 in the container.</entry> | |
464 | </row> | |
465 | ||
466 | <row> | |
467 | <entry><option>--as-pid2</option> specified</entry> | |
468 | <entry>The passed parameters are interpreted as the command line, which is executed as PID 2 in the container. A stub init process is run as PID 1.</entry> | |
469 | </row> | |
470 | ||
471 | <row> | |
472 | <entry><option>--boot</option> specified</entry> | |
473 | <entry>An init program is automatically searched for and run as PID 1 in the container. The passed parameters are used as invocation parameters for this process.</entry> | |
474 | </row> | |
475 | ||
476 | </tbody> | |
477 | </tgroup> | |
478 | </table> | |
479 | ||
480 | <para>Note that <option>--boot</option> is the default mode of operation if the | |
481 | <filename>systemd-nspawn@.service</filename> template unit file is used.</para> | |
482 | </listitem> | |
483 | </varlistentry> | |
484 | ||
485 | <varlistentry> | |
486 | <term><option>--chdir=</option></term> | |
487 | ||
488 | <listitem><para>Change to the specified working directory before invoking the process in the container. Expects | |
489 | an absolute path in the container's file system namespace.</para></listitem> | |
490 | </varlistentry> | |
491 | ||
492 | <varlistentry> | |
493 | <term><option>-E <replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term> | |
494 | <term><option>--setenv=<replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term> | |
495 | ||
496 | <listitem><para>Specifies an environment variable assignment | |
497 | to pass to the init process in the container, in the format | |
498 | <literal>NAME=VALUE</literal>. This may be used to override | |
499 | the default variables or to set additional variables. This | |
500 | parameter may be used more than once.</para></listitem> | |
501 | </varlistentry> | |
502 | ||
503 | <varlistentry> | |
504 | <term><option>-u</option></term> | |
505 | <term><option>--user=</option></term> | |
506 | ||
507 | <listitem><para>After transitioning into the container, change | |
508 | to the specified user-defined in the container's user | |
509 | database. Like all other systemd-nspawn features, this is not | |
510 | a security feature and provides protection against accidental | |
511 | destructive operations only.</para></listitem> | |
512 | </varlistentry> | |
513 | ||
514 | <varlistentry> | |
515 | <term><option>--kill-signal=</option></term> | |
516 | ||
517 | <listitem><para>Specify the process signal to send to the container's PID 1 when nspawn itself receives | |
518 | <constant>SIGTERM</constant>, in order to trigger an orderly shutdown of the container. Defaults to | |
519 | <constant>SIGRTMIN+3</constant> if <option>--boot</option> is used (on systemd-compatible init systems | |
520 | <constant>SIGRTMIN+3</constant> triggers an orderly shutdown). If <option>--boot</option> is not used and this | |
521 | option is not specified the container's processes are terminated abruptly via <constant>SIGKILL</constant>. For | |
522 | a list of valid signals, see <citerefentry | |
523 | project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem> | |
524 | </varlistentry> | |
525 | ||
526 | <varlistentry> | |
527 | <term><option>--notify-ready=</option></term> | |
528 | ||
529 | <listitem><para>Configures support for notifications from the container's init process. | |
530 | <option>--notify-ready=</option> takes a boolean (<option>no</option> and <option>yes</option>). | |
531 | With option <option>no</option> systemd-nspawn notifies systemd | |
532 | with a <literal>READY=1</literal> message when the init process is created. | |
533 | With option <option>yes</option> systemd-nspawn waits for the | |
534 | <literal>READY=1</literal> message from the init process in the container | |
535 | before sending its own to systemd. For more details about notifications | |
536 | see <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).</para></listitem> | |
537 | </varlistentry> | |
538 | </variablelist> | |
539 | ||
540 | </refsect2><refsect2> | |
541 | <title>System Identity Options</title> | |
542 | ||
543 | <variablelist> | |
544 | <varlistentry> | |
545 | <term><option>-M</option></term> | |
546 | <term><option>--machine=</option></term> | |
547 | ||
548 | <listitem><para>Sets the machine name for this container. This | |
549 | name may be used to identify this container during its runtime | |
550 | (for example in tools like | |
551 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
552 | and similar), and is used to initialize the container's | |
553 | hostname (which the container can choose to override, | |
554 | however). If not specified, the last component of the root | |
555 | directory path of the container is used, possibly suffixed | |
556 | with a random identifier in case <option>--ephemeral</option> | |
557 | mode is selected. If the root directory selected is the host's | |
558 | root directory the host's hostname is used as default | |
559 | instead.</para></listitem> | |
560 | </varlistentry> | |
561 | ||
562 | <varlistentry> | |
563 | <term><option>--hostname=</option></term> | |
564 | ||
565 | <listitem><para>Controls the hostname to set within the container, if different from the machine name. Expects | |
566 | a valid hostname as argument. If this option is used, the kernel hostname of the container will be set to this | |
567 | value, otherwise it will be initialized to the machine name as controlled by the <option>--machine=</option> | |
568 | option described above. The machine name is used for various aspect of identification of the container from the | |
569 | outside, the kernel hostname configurable with this option is useful for the container to identify itself from | |
570 | the inside. It is usually a good idea to keep both forms of identification synchronized, in order to avoid | |
571 | confusion. It is hence recommended to avoid usage of this option, and use <option>--machine=</option> | |
572 | exclusively. Note that regardless whether the container's hostname is initialized from the name set with | |
573 | <option>--hostname=</option> or the one set with <option>--machine=</option>, the container can later override | |
574 | its kernel hostname freely on its own as well.</para> | |
575 | </listitem> | |
576 | </varlistentry> | |
577 | ||
578 | <varlistentry> | |
579 | <term><option>--uuid=</option></term> | |
580 | ||
581 | <listitem><para>Set the specified UUID for the container. The | |
582 | init system will initialize | |
583 | <filename>/etc/machine-id</filename> from this if this file is | |
584 | not set yet. Note that this option takes effect only if | |
585 | <filename>/etc/machine-id</filename> in the container is | |
586 | unpopulated.</para></listitem> | |
587 | </varlistentry> | |
588 | </variablelist> | |
589 | ||
590 | </refsect2><refsect2> | |
591 | <title>Property Options</title> | |
592 | ||
593 | <variablelist> | |
594 | <varlistentry> | |
595 | <term><option>-S</option></term> | |
596 | <term><option>--slice=</option></term> | |
597 | ||
598 | <listitem><para>Make the container part of the specified slice, instead of the default | |
599 | <filename>machine.slice</filename>. This applies only if the machine is run in its own scope unit, i.e. if | |
600 | <option>--keep-unit</option> isn't used.</para> | |
601 | </listitem> | |
602 | </varlistentry> | |
603 | ||
604 | <varlistentry> | |
605 | <term><option>--property=</option></term> | |
606 | ||
607 | <listitem><para>Set a unit property on the scope unit to register for the machine. This applies only if the | |
608 | machine is run in its own scope unit, i.e. if <option>--keep-unit</option> isn't used. Takes unit property | |
609 | assignments in the same format as <command>systemctl set-property</command>. This is useful to set memory | |
610 | limits and similar for container.</para> | |
611 | </listitem> | |
612 | </varlistentry> | |
613 | ||
614 | <varlistentry> | |
615 | <term><option>--register=</option></term> | |
616 | ||
617 | <listitem><para>Controls whether the container is registered with | |
618 | <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes a | |
619 | boolean argument, which defaults to <literal>yes</literal>. This option should be enabled when the container | |
620 | runs a full Operating System (more specifically: a system and service manager as PID 1), and is useful to | |
621 | ensure that the container is accessible via | |
622 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> and shown by | |
623 | tools such as <citerefentry | |
624 | project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If the container | |
625 | does not run a service manager, it is recommended to set this option to | |
626 | <literal>no</literal>.</para></listitem> | |
627 | </varlistentry> | |
628 | ||
629 | <varlistentry> | |
630 | <term><option>--keep-unit</option></term> | |
631 | ||
632 | <listitem><para>Instead of creating a transient scope unit to run the container in, simply use the service or | |
633 | scope unit <command>systemd-nspawn</command> has been invoked in. If <option>--register=yes</option> is set | |
634 | this unit is registered with | |
635 | <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This | |
636 | switch should be used if <command>systemd-nspawn</command> is invoked from within a service unit, and the | |
637 | service unit's sole purpose is to run a single <command>systemd-nspawn</command> container. This option is not | |
638 | available if run from a user session.</para> | |
639 | <para>Note that passing <option>--keep-unit</option> disables the effect of <option>--slice=</option> and | |
640 | <option>--property=</option>. Use <option>--keep-unit</option> and <option>--register=no</option> in | |
641 | combination to disable any kind of unit allocation or registration with | |
642 | <command>systemd-machined</command>.</para></listitem> | |
643 | </varlistentry> | |
644 | </variablelist> | |
645 | ||
646 | </refsect2><refsect2> | |
647 | <title>User Namespacing Options</title> | |
648 | ||
649 | <variablelist> | |
650 | <varlistentry> | |
651 | <term><option>--private-users=</option></term> | |
652 | ||
653 | <listitem><para>Controls user namespacing. If enabled, the container will run with its own private set of UNIX | |
654 | user and group ids (UIDs and GIDs). This involves mapping the private UIDs/GIDs used in the container (starting | |
655 | with the container's root user 0 and up) to a range of UIDs/GIDs on the host that are not used for other | |
656 | purposes (usually in the range beyond the host's UID/GID 65536). The parameter may be specified as follows:</para> | |
657 | ||
658 | <orderedlist> | |
659 | <listitem><para>If one or two colon-separated numbers are specified, user namespacing is turned on. The first | |
660 | parameter specifies the first host UID/GID to assign to the container, the second parameter specifies the | |
661 | number of host UIDs/GIDs to assign to the container. If the second parameter is omitted, 65536 UIDs/GIDs are | |
662 | assigned.</para></listitem> | |
663 | ||
664 | <listitem><para>If the parameter is omitted, or true, user namespacing is turned on. The UID/GID range to | |
665 | use is determined automatically from the file ownership of the root directory of the container's directory | |
666 | tree. To use this option, make sure to prepare the directory tree in advance, and ensure that all files and | |
667 | directories in it are owned by UIDs/GIDs in the range you'd like to use. Also, make sure that used file ACLs | |
668 | exclusively reference UIDs/GIDs in the appropriate range. If this mode is used the number of UIDs/GIDs | |
669 | assigned to the container for use is 65536, and the UID/GID of the root directory must be a multiple of | |
670 | 65536.</para></listitem> | |
671 | ||
672 | <listitem><para>If the parameter is false, user namespacing is turned off. This is the default.</para> | |
673 | </listitem> | |
674 | ||
675 | <listitem><para>The special value <literal>pick</literal> turns on user namespacing. In this case the UID/GID | |
676 | range is automatically chosen. As first step, the file owner of the root directory of the container's | |
677 | directory tree is read, and it is checked that it is currently not used by the system otherwise (in | |
678 | particular, that no other container is using it). If this check is successful, the UID/GID range determined | |
679 | this way is used, similar to the behavior if "yes" is specified. If the check is not successful (and thus | |
680 | the UID/GID range indicated in the root directory's file owner is already used elsewhere) a new – currently | |
681 | unused – UID/GID range of 65536 UIDs/GIDs is randomly chosen between the host UID/GIDs of 524288 and | |
682 | 1878982656, always starting at a multiple of 65536. This setting implies | |
683 | <option>--private-users-chown</option> (see below), which has the effect that the files and directories in | |
684 | the container's directory tree will be owned by the appropriate users of the range picked. Using this option | |
685 | makes user namespace behavior fully automatic. Note that the first invocation of a previously unused | |
686 | container image might result in picking a new UID/GID range for it, and thus in the (possibly expensive) file | |
687 | ownership adjustment operation. However, subsequent invocations of the container will be cheap (unless of | |
688 | course the picked UID/GID range is assigned to a different use by then).</para></listitem> | |
689 | </orderedlist> | |
690 | ||
691 | <para>It is recommended to assign at least 65536 UIDs/GIDs to each container, so that the usable UID/GID range in the | |
692 | container covers 16 bit. For best security, do not assign overlapping UID/GID ranges to multiple containers. It is | |
693 | hence a good idea to use the upper 16 bit of the host 32-bit UIDs/GIDs as container identifier, while the lower 16 | |
694 | bit encode the container UID/GID used. This is in fact the behavior enforced by the | |
695 | <option>--private-users=pick</option> option.</para> | |
696 | ||
697 | <para>When user namespaces are used, the GID range assigned to each container is always chosen identical to the | |
698 | UID range.</para> | |
699 | ||
700 | <para>In most cases, using <option>--private-users=pick</option> is the recommended option as it enhances | |
701 | container security massively and operates fully automatically in most cases.</para> | |
702 | ||
703 | <para>Note that the picked UID/GID range is not written to <filename>/etc/passwd</filename> or | |
704 | <filename>/etc/group</filename>. In fact, the allocation of the range is not stored persistently anywhere, | |
705 | except in the file ownership of the files and directories of the container.</para> | |
706 | ||
707 | <para>Note that when user namespacing is used file ownership on disk reflects this, and all of the container's | |
708 | files and directories are owned by the container's effective user and group IDs. This means that copying files | |
709 | from and to the container image requires correction of the numeric UID/GID values, according to the UID/GID | |
710 | shift applied.</para></listitem> | |
711 | </varlistentry> | |
712 | ||
713 | <varlistentry> | |
714 | <term><option>--private-users-chown</option></term> | |
715 | ||
716 | <listitem><para>If specified, all files and directories in the container's directory tree will be | |
717 | adjusted so that they are owned by the appropriate UIDs/GIDs selected for the container (see above). | |
718 | This operation is potentially expensive, as it involves iterating through the full directory tree of | |
719 | the container. Besides actual file ownership, file ACLs are adjusted as well.</para> | |
720 | ||
721 | <para>This option is implied if <option>--private-users=pick</option> is used. This option has no effect if | |
722 | user namespacing is not used.</para></listitem> | |
723 | </varlistentry> | |
724 | ||
725 | <varlistentry> | |
726 | <term><option>-U</option></term> | |
727 | ||
728 | <listitem><para>If the kernel supports the user namespaces feature, equivalent to | |
729 | <option>--private-users=pick --private-users-chown</option>, otherwise equivalent to | |
730 | <option>--private-users=no</option>.</para> | |
731 | ||
732 | <para>Note that <option>-U</option> is the default if the | |
733 | <filename>systemd-nspawn@.service</filename> template unit file is used.</para> | |
734 | ||
735 | <para>Note: it is possible to undo the effect of <option>--private-users-chown</option> (or | |
736 | <option>-U</option>) on the file system by redoing the operation with the first UID of 0:</para> | |
737 | ||
738 | <programlisting>systemd-nspawn … --private-users=0 --private-users-chown</programlisting> | |
739 | </listitem> | |
740 | </varlistentry> | |
741 | ||
742 | </variablelist> | |
743 | ||
744 | </refsect2><refsect2> | |
745 | <title>Networking Options</title> | |
746 | ||
747 | <variablelist> | |
748 | ||
749 | <varlistentry> | |
750 | <term><option>--private-network</option></term> | |
751 | ||
752 | <listitem><para>Disconnect networking of the container from | |
753 | the host. This makes all network interfaces unavailable in the | |
754 | container, with the exception of the loopback device and those | |
755 | specified with <option>--network-interface=</option> and | |
756 | configured with <option>--network-veth</option>. If this | |
757 | option is specified, the CAP_NET_ADMIN capability will be | |
758 | added to the set of capabilities the container retains. The | |
759 | latter may be disabled by using <option>--drop-capability=</option>. | |
760 | If this option is not specified (or implied by one of the options | |
761 | listed below), the container will have full access to the host network. | |
762 | </para></listitem> | |
763 | </varlistentry> | |
764 | ||
765 | <varlistentry> | |
766 | <term><option>--network-interface=</option></term> | |
767 | ||
768 | <listitem><para>Assign the specified network interface to the | |
769 | container. This will remove the specified interface from the | |
770 | calling namespace and place it in the container. When the | |
771 | container terminates, it is moved back to the host namespace. | |
772 | Note that <option>--network-interface=</option> implies | |
773 | <option>--private-network</option>. This option may be used | |
774 | more than once to add multiple network interfaces to the | |
775 | container.</para></listitem> | |
776 | </varlistentry> | |
777 | ||
778 | <varlistentry> | |
779 | <term><option>--network-macvlan=</option></term> | |
780 | ||
781 | <listitem><para>Create a <literal>macvlan</literal> interface | |
782 | of the specified Ethernet network interface and add it to the | |
783 | container. A <literal>macvlan</literal> interface is a virtual | |
784 | interface that adds a second MAC address to an existing | |
785 | physical Ethernet link. The interface in the container will be | |
786 | named after the interface on the host, prefixed with | |
787 | <literal>mv-</literal>. Note that | |
788 | <option>--network-macvlan=</option> implies | |
789 | <option>--private-network</option>. This option may be used | |
790 | more than once to add multiple network interfaces to the | |
791 | container.</para></listitem> | |
792 | </varlistentry> | |
793 | ||
794 | <varlistentry> | |
795 | <term><option>--network-ipvlan=</option></term> | |
796 | ||
797 | <listitem><para>Create an <literal>ipvlan</literal> interface | |
798 | of the specified Ethernet network interface and add it to the | |
799 | container. An <literal>ipvlan</literal> interface is a virtual | |
800 | interface, similar to a <literal>macvlan</literal> interface, | |
801 | which uses the same MAC address as the underlying interface. | |
802 | The interface in the container will be named after the | |
803 | interface on the host, prefixed with <literal>iv-</literal>. | |
804 | Note that <option>--network-ipvlan=</option> implies | |
805 | <option>--private-network</option>. This option may be used | |
806 | more than once to add multiple network interfaces to the | |
807 | container.</para></listitem> | |
808 | </varlistentry> | |
809 | ||
810 | <varlistentry> | |
811 | <term><option>-n</option></term> | |
812 | <term><option>--network-veth</option></term> | |
813 | ||
814 | <listitem><para>Create a virtual Ethernet link (<literal>veth</literal>) between host and container. The host | |
815 | side of the Ethernet link will be available as a network interface named after the container's name (as | |
816 | specified with <option>--machine=</option>), prefixed with <literal>ve-</literal>. The container side of the | |
817 | Ethernet link will be named <literal>host0</literal>. The <option>--network-veth</option> option implies | |
818 | <option>--private-network</option>.</para> | |
819 | ||
820 | <para>Note that | |
821 | <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
822 | includes by default a network file <filename>/usr/lib/systemd/network/80-container-ve.network</filename> | |
823 | matching the host-side interfaces created this way, which contains settings to enable automatic address | |
824 | provisioning on the created virtual link via DHCP, as well as automatic IP routing onto the host's external | |
825 | network interfaces. It also contains <filename>/usr/lib/systemd/network/80-container-host0.network</filename> | |
826 | matching the container-side interface created this way, containing settings to enable client side address | |
827 | assignment via DHCP. In case <filename>systemd-networkd</filename> is running on both the host and inside the | |
828 | container, automatic IP communication from the container to the host is thus available, with further | |
829 | connectivity to the external network.</para> | |
830 | ||
831 | <para>Note that <option>--network-veth</option> is the default if the | |
832 | <filename>systemd-nspawn@.service</filename> template unit file is used.</para> | |
833 | ||
834 | <para>Note that on Linux network interface names may have a length of 15 characters at maximum, while | |
835 | container names may have a length up to 64 characters. As this option derives the host-side interface | |
836 | name from the container name the name is possibly truncated. Thus, care needs to be taken to ensure | |
837 | that interface names remain unique in this case, or even better container names are generally not | |
838 | chosen longer than 12 characters, to avoid the truncation. Alternatively, the | |
839 | <option>--network-veth-extra=</option> option may be used, which allows free configuration of the | |
840 | host-side interface name independently of the container name — but might require a bit more | |
841 | additional configuration in case bridging in a fashion similar to <option>--network-bridge=</option> | |
842 | is desired.</para> | |
843 | </listitem> | |
844 | </varlistentry> | |
845 | ||
846 | <varlistentry> | |
847 | <term><option>--network-veth-extra=</option></term> | |
848 | ||
849 | <listitem><para>Adds an additional virtual Ethernet link | |
850 | between host and container. Takes a colon-separated pair of | |
851 | host interface name and container interface name. The latter | |
852 | may be omitted in which case the container and host sides will | |
853 | be assigned the same name. This switch is independent of | |
854 | <option>--network-veth</option>, and — in contrast — may be | |
855 | used multiple times, and allows configuration of the network | |
856 | interface names. Note that <option>--network-bridge=</option> | |
857 | has no effect on interfaces created with | |
858 | <option>--network-veth-extra=</option>.</para></listitem> | |
859 | </varlistentry> | |
860 | ||
861 | <varlistentry> | |
862 | <term><option>--network-bridge=</option></term> | |
863 | ||
864 | <listitem><para>Adds the host side of the Ethernet link created with <option>--network-veth</option> | |
865 | to the specified Ethernet bridge interface. Expects a valid network interface name of a bridge device | |
866 | as argument. Note that <option>--network-bridge=</option> implies <option>--network-veth</option>. If | |
867 | this option is used, the host side of the Ethernet link will use the <literal>vb-</literal> prefix | |
868 | instead of <literal>ve-</literal>. Regardless of the used naming prefix the same network interface | |
869 | name length limits imposed by Linux apply, along with the complications this creates (for details see | |
870 | above).</para></listitem> | |
871 | </varlistentry> | |
872 | ||
873 | <varlistentry> | |
874 | <term><option>--network-zone=</option></term> | |
875 | ||
876 | <listitem><para>Creates a virtual Ethernet link (<literal>veth</literal>) to the container and adds it to an | |
877 | automatically managed Ethernet bridge interface. The bridge interface is named after the passed argument, | |
878 | prefixed with <literal>vz-</literal>. The bridge interface is automatically created when the first container | |
879 | configured for its name is started, and is automatically removed when the last container configured for its | |
880 | name exits. Hence, each bridge interface configured this way exists only as long as there's at least one | |
881 | container referencing it running. This option is very similar to <option>--network-bridge=</option>, besides | |
882 | this automatic creation/removal of the bridge device.</para> | |
883 | ||
884 | <para>This setting makes it easy to place multiple related containers on a common, virtual Ethernet-based | |
885 | broadcast domain, here called a "zone". Each container may only be part of one zone, but each zone may contain | |
886 | any number of containers. Each zone is referenced by its name. Names may be chosen freely (as long as they form | |
887 | valid network interface names when prefixed with <literal>vz-</literal>), and it is sufficient to pass the same | |
888 | name to the <option>--network-zone=</option> switch of the various concurrently running containers to join | |
889 | them in one zone.</para> | |
890 | ||
891 | <para>Note that | |
892 | <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
893 | includes by default a network file <filename>/usr/lib/systemd/network/80-container-vz.network</filename> | |
894 | matching the bridge interfaces created this way, which contains settings to enable automatic address | |
895 | provisioning on the created virtual network via DHCP, as well as automatic IP routing onto the host's external | |
896 | network interfaces. Using <option>--network-zone=</option> is hence in most cases fully automatic and | |
897 | sufficient to connect multiple local containers in a joined broadcast domain to the host, with further | |
898 | connectivity to the external network.</para> | |
899 | </listitem> | |
900 | </varlistentry> | |
901 | ||
902 | <varlistentry> | |
903 | <term><option>--network-namespace-path=</option></term> | |
904 | ||
905 | <listitem><para>Takes the path to a file representing a kernel | |
906 | network namespace that the container shall run in. The specified path | |
907 | should refer to a (possibly bind-mounted) network namespace file, as | |
908 | exposed by the kernel below <filename>/proc/$PID/ns/net</filename>. | |
909 | This makes the container enter the given network namespace. One of the | |
910 | typical use cases is to give a network namespace under | |
911 | <filename>/run/netns</filename> created by <citerefentry | |
912 | project='man-pages'><refentrytitle>ip-netns</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
913 | for example, <option>--network-namespace-path=/run/netns/foo</option>. | |
914 | Note that this option cannot be used together with other | |
915 | network-related options, such as <option>--private-network</option> | |
916 | or <option>--network-interface=</option>.</para></listitem> | |
917 | </varlistentry> | |
918 | ||
919 | <varlistentry> | |
920 | <term><option>-p</option></term> | |
921 | <term><option>--port=</option></term> | |
922 | ||
923 | <listitem><para>If private networking is enabled, maps an IP | |
924 | port on the host onto an IP port on the container. Takes a | |
925 | protocol specifier (either <literal>tcp</literal> or | |
926 | <literal>udp</literal>), separated by a colon from a host port | |
927 | number in the range 1 to 65535, separated by a colon from a | |
928 | container port number in the range from 1 to 65535. The | |
929 | protocol specifier and its separating colon may be omitted, in | |
930 | which case <literal>tcp</literal> is assumed. The container | |
931 | port number and its colon may be omitted, in which case the | |
932 | same port as the host port is implied. This option is only | |
933 | supported if private networking is used, such as with | |
934 | <option>--network-veth</option>, <option>--network-zone=</option> | |
935 | <option>--network-bridge=</option>.</para></listitem> | |
936 | </varlistentry> | |
937 | </variablelist> | |
938 | ||
939 | </refsect2><refsect2> | |
940 | <title>Security Options</title> | |
941 | ||
942 | <variablelist> | |
943 | <varlistentry> | |
944 | <term><option>--capability=</option></term> | |
945 | ||
946 | <listitem><para>List one or more additional capabilities to grant the container. | |
947 | Takes a comma-separated list of capability names, see | |
948 | <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
949 | for more information. Note that the following capabilities will be granted in any way: | |
950 | CAP_AUDIT_CONTROL, CAP_AUDIT_WRITE, CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, | |
951 | CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER, CAP_KILL, CAP_LEASE, CAP_LINUX_IMMUTABLE, | |
952 | CAP_MKNOD, CAP_NET_BIND_SERVICE, CAP_NET_BROADCAST, CAP_NET_RAW, CAP_SETFCAP, | |
953 | CAP_SETGID, CAP_SETPCAP, CAP_SETUID, CAP_SYS_ADMIN, CAP_SYS_BOOT, CAP_SYS_CHROOT, | |
954 | CAP_SYS_NICE, CAP_SYS_PTRACE, CAP_SYS_RESOURCE, CAP_SYS_TTY_CONFIG. Also CAP_NET_ADMIN | |
955 | is retained if <option>--private-network</option> is specified. If the special value | |
956 | <literal>all</literal> is passed, all capabilities are retained.</para></listitem> | |
957 | </varlistentry> | |
958 | ||
959 | <varlistentry> | |
960 | <term><option>--drop-capability=</option></term> | |
961 | ||
962 | <listitem><para>Specify one or more additional capabilities to | |
963 | drop for the container. This allows running the container with | |
964 | fewer capabilities than the default (see | |
965 | above).</para></listitem> | |
966 | </varlistentry> | |
967 | ||
968 | <varlistentry> | |
969 | <term><option>--no-new-privileges=</option></term> | |
970 | ||
971 | <listitem><para>Takes a boolean argument. Specifies the value of the <constant>PR_SET_NO_NEW_PRIVS</constant> | |
972 | flag for the container payload. Defaults to off. When turned on the payload code of the container cannot | |
973 | acquire new privileges, i.e. the "setuid" file bit as well as file system capabilities will not have an effect | |
974 | anymore. See <citerefentry | |
975 | project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details | |
976 | about this flag. </para></listitem> | |
977 | </varlistentry> | |
978 | ||
979 | <varlistentry> | |
980 | <term><option>--system-call-filter=</option></term> | |
981 | ||
982 | <listitem><para>Alter the system call filter applied to containers. Takes a space-separated list of system call | |
983 | names or group names (the latter prefixed with <literal>@</literal>, as listed by the | |
984 | <command>syscall-filter</command> command of | |
985 | <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Passed | |
986 | system calls will be permitted. The list may optionally be prefixed by <literal>~</literal>, in which case all | |
987 | listed system calls are prohibited. If this command line option is used multiple times the configured lists are | |
988 | combined. If both a positive and a negative list (that is one system call list without and one with the | |
989 | <literal>~</literal> prefix) are configured, the negative list takes precedence over the positive list. Note | |
990 | that <command>systemd-nspawn</command> always implements a system call whitelist (as opposed to a blacklist), | |
991 | and this command line option hence adds or removes entries from the default whitelist, depending on the | |
992 | <literal>~</literal> prefix. Note that the applied system call filter is also altered implicitly if additional | |
993 | capabilities are passed using the <command>--capabilities=</command>.</para></listitem> | |
994 | </varlistentry> | |
995 | ||
996 | <varlistentry> | |
997 | <term><option>-Z</option></term> | |
998 | <term><option>--selinux-context=</option></term> | |
999 | ||
1000 | <listitem><para>Sets the SELinux security context to be used | |
1001 | to label processes in the container.</para> | |
1002 | </listitem> | |
1003 | </varlistentry> | |
1004 | ||
1005 | <varlistentry> | |
1006 | <term><option>-L</option></term> | |
1007 | <term><option>--selinux-apifs-context=</option></term> | |
1008 | ||
1009 | <listitem><para>Sets the SELinux security context to be used | |
1010 | to label files in the virtual API file systems in the | |
1011 | container.</para> | |
1012 | </listitem> | |
1013 | </varlistentry> | |
1014 | </variablelist> | |
1015 | ||
1016 | </refsect2><refsect2> | |
1017 | <title>Resource Options</title> | |
1018 | ||
1019 | <variablelist> | |
1020 | ||
1021 | <varlistentry> | |
1022 | <term><option>--rlimit=</option></term> | |
1023 | ||
1024 | <listitem><para>Sets the specified POSIX resource limit for the container payload. Expects an assignment of the | |
1025 | form | |
1026 | <literal><replaceable>LIMIT</replaceable>=<replaceable>SOFT</replaceable>:<replaceable>HARD</replaceable></literal> | |
1027 | or <literal><replaceable>LIMIT</replaceable>=<replaceable>VALUE</replaceable></literal>, where | |
1028 | <replaceable>LIMIT</replaceable> should refer to a resource limit type, such as | |
1029 | <constant>RLIMIT_NOFILE</constant> or <constant>RLIMIT_NICE</constant>. The <replaceable>SOFT</replaceable> and | |
1030 | <replaceable>HARD</replaceable> fields should refer to the numeric soft and hard resource limit values. If the | |
1031 | second form is used, <replaceable>VALUE</replaceable> may specify a value that is used both as soft and hard | |
1032 | limit. In place of a numeric value the special string <literal>infinity</literal> may be used to turn off | |
1033 | resource limiting for the specific type of resource. This command line option may be used multiple times to | |
1034 | control limits on multiple limit types. If used multiple times for the same limit type, the last use | |
1035 | wins. For details about resource limits see <citerefentry | |
1036 | project='man-pages'><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>. By default | |
1037 | resource limits for the container's init process (PID 1) are set to the same values the Linux kernel originally | |
1038 | passed to the host init system. Note that some resource limits are enforced on resources counted per user, in | |
1039 | particular <constant>RLIMIT_NPROC</constant>. This means that unless user namespacing is deployed | |
1040 | (i.e. <option>--private-users=</option> is used, see above), any limits set will be applied to the resource | |
1041 | usage of the same user on all local containers as well as the host. This means particular care needs to be | |
1042 | taken with these limits as they might be triggered by possibly less trusted code. Example: | |
1043 | <literal>--rlimit=RLIMIT_NOFILE=8192:16384</literal>.</para></listitem> | |
1044 | </varlistentry> | |
1045 | ||
1046 | <varlistentry> | |
1047 | <term><option>--oom-score-adjust=</option></term> | |
1048 | ||
1049 | <listitem><para>Changes the OOM ("Out Of Memory") score adjustment value for the container payload. This controls | |
1050 | <filename>/proc/self/oom_score_adj</filename> which influences the preference with which this container is | |
1051 | terminated when memory becomes scarce. For details see <citerefentry | |
1052 | project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Takes an | |
1053 | integer in the range -1000…1000.</para></listitem> | |
1054 | </varlistentry> | |
1055 | ||
1056 | <varlistentry> | |
1057 | <term><option>--cpu-affinity=</option></term> | |
1058 | ||
1059 | <listitem><para>Controls the CPU affinity of the container payload. Takes a comma separated list of CPU numbers | |
1060 | or number ranges (the latter's start and end value separated by dashes). See <citerefentry | |
1061 | project='man-pages'><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry> for | |
1062 | details.</para></listitem> | |
1063 | </varlistentry> | |
1064 | ||
1065 | <varlistentry> | |
1066 | <term><option>--personality=</option></term> | |
1067 | ||
1068 | <listitem><para>Control the architecture ("personality") | |
1069 | reported by | |
1070 | <citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
1071 | in the container. Currently, only <literal>x86</literal> and | |
1072 | <literal>x86-64</literal> are supported. This is useful when | |
1073 | running a 32-bit container on a 64-bit host. If this setting | |
1074 | is not used, the personality reported in the container is the | |
1075 | same as the one reported on the host.</para></listitem> | |
1076 | </varlistentry> | |
1077 | </variablelist> | |
1078 | ||
1079 | </refsect2><refsect2> | |
1080 | <title>Integration Options</title> | |
1081 | ||
1082 | <variablelist> | |
1083 | <varlistentry> | |
1084 | <term><option>--resolv-conf=</option></term> | |
1085 | ||
1086 | <listitem><para>Configures how <filename>/etc/resolv.conf</filename> inside of the container (i.e. DNS | |
1087 | configuration synchronization from host to container) shall be handled. Takes one of <literal>off</literal>, | |
1088 | <literal>copy-host</literal>, <literal>copy-static</literal>, <literal>bind-host</literal>, | |
1089 | <literal>bind-static</literal>, <literal>delete</literal> or <literal>auto</literal>. If set to | |
1090 | <literal>off</literal> the <filename>/etc/resolv.conf</filename> file in the container is left as it is | |
1091 | included in the image, and neither modified nor bind mounted over. If set to <literal>copy-host</literal>, the | |
1092 | <filename>/etc/resolv.conf</filename> file from the host is copied into the container. Similar, if | |
1093 | <literal>bind-host</literal> is used, the file is bind mounted from the host into the container. If set to | |
1094 | <literal>copy-static</literal> the static <filename>resolv.conf</filename> file supplied with | |
1095 | <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> is | |
1096 | copied into the container, and correspondingly <literal>bind-static</literal> bind mounts it there. If set to | |
1097 | <literal>delete</literal> the <filename>/etc/resolv.conf</filename> file in the container is deleted if it | |
1098 | exists. Finally, if set to <literal>auto</literal> the file is left as it is if private networking is turned on | |
1099 | (see <option>--private-network</option>). Otherwise, if <filename>systemd-resolved.service</filename> is | |
1100 | connectible its static <filename>resolv.conf</filename> file is used, and if not the host's | |
1101 | <filename>/etc/resolv.conf</filename> file is used. In the latter cases the file is copied if the image is | |
1102 | writable, and bind mounted otherwise. It's recommended to use <literal>copy</literal> if the container shall be | |
1103 | able to make changes to the DNS configuration on its own, deviating from the host's settings. Otherwise | |
1104 | <literal>bind</literal> is preferable, as it means direct changes to <filename>/etc/resolv.conf</filename> in | |
1105 | the container are not allowed, as it is a read-only bind mount (but note that if the container has enough | |
1106 | privileges, it might simply go ahead and unmount the bind mount anyway). Note that both if the file is bind | |
1107 | mounted and if it is copied no further propagation of configuration is generally done after the one-time early | |
1108 | initialization (this is because the file is usually updated through copying and renaming). Defaults to | |
1109 | <literal>auto</literal>.</para></listitem> | |
1110 | </varlistentry> | |
1111 | ||
1112 | <varlistentry> | |
1113 | <term><option>--timezone=</option></term> | |
1114 | ||
1115 | <listitem><para>Configures how <filename>/etc/localtime</filename> inside of the container (i.e. local timezone | |
1116 | synchronization from host to container) shall be handled. Takes one of <literal>off</literal>, | |
1117 | <literal>copy</literal>, <literal>bind</literal>, <literal>symlink</literal>, <literal>delete</literal> or | |
1118 | <literal>auto</literal>. If set to <literal>off</literal> the <filename>/etc/localtime</filename> file in the | |
1119 | container is left as it is included in the image, and neither modified nor bind mounted over. If set to | |
1120 | <literal>copy</literal> the <filename>/etc/localtime</filename> file of the host is copied into the | |
1121 | container. Similar, if <literal>bind</literal> is used, it is bind mounted from the host into the container. If | |
1122 | set to <literal>symlink</literal> a symlink from <filename>/etc/localtime</filename> in the container is | |
1123 | created pointing to the matching the timezone file of the container that matches the timezone setting on the | |
1124 | host. If set to <literal>delete</literal> the file in the container is deleted, should it exist. If set to | |
1125 | <literal>auto</literal> and the <filename>/etc/localtime</filename> file of the host is a symlink, then | |
1126 | <literal>symlink</literal> mode is used, and <literal>copy</literal> otherwise, except if the image is | |
1127 | read-only in which case <literal>bind</literal> is used instead. Defaults to | |
1128 | <literal>auto</literal>.</para></listitem> | |
1129 | </varlistentry> | |
1130 | ||
1131 | <varlistentry> | |
1132 | <term><option>--link-journal=</option></term> | |
1133 | ||
1134 | <listitem><para>Control whether the container's journal shall | |
1135 | be made visible to the host system. If enabled, allows viewing | |
1136 | the container's journal files from the host (but not vice | |
1137 | versa). Takes one of <literal>no</literal>, | |
1138 | <literal>host</literal>, <literal>try-host</literal>, | |
1139 | <literal>guest</literal>, <literal>try-guest</literal>, | |
1140 | <literal>auto</literal>. If <literal>no</literal>, the journal | |
1141 | is not linked. If <literal>host</literal>, the journal files | |
1142 | are stored on the host file system (beneath | |
1143 | <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>) | |
1144 | and the subdirectory is bind-mounted into the container at the | |
1145 | same location. If <literal>guest</literal>, the journal files | |
1146 | are stored on the guest file system (beneath | |
1147 | <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>) | |
1148 | and the subdirectory is symlinked into the host at the same | |
1149 | location. <literal>try-host</literal> and | |
1150 | <literal>try-guest</literal> do the same but do not fail if | |
1151 | the host does not have persistent journaling enabled. If | |
1152 | <literal>auto</literal> (the default), and the right | |
1153 | subdirectory of <filename>/var/log/journal</filename> exists, | |
1154 | it will be bind mounted into the container. If the | |
1155 | subdirectory does not exist, no linking is performed. | |
1156 | Effectively, booting a container once with | |
1157 | <literal>guest</literal> or <literal>host</literal> will link | |
1158 | the journal persistently if further on the default of | |
1159 | <literal>auto</literal> is used.</para> | |
1160 | ||
1161 | <para>Note that <option>--link-journal=try-guest</option> is the default if the | |
1162 | <filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem> | |
1163 | </varlistentry> | |
1164 | ||
1165 | <varlistentry> | |
1166 | <term><option>-j</option></term> | |
1167 | ||
1168 | <listitem><para>Equivalent to | |
1169 | <option>--link-journal=try-guest</option>.</para></listitem> | |
1170 | </varlistentry> | |
1171 | ||
1172 | </variablelist> | |
1173 | ||
1174 | </refsect2><refsect2> | |
1175 | <title>Mount Options</title> | |
1176 | ||
1177 | <variablelist> | |
1178 | ||
1179 | <varlistentry> | |
1180 | <term><option>--bind=</option></term> | |
1181 | <term><option>--bind-ro=</option></term> | |
1182 | ||
1183 | <listitem><para>Bind mount a file or directory from the host into the container. Takes one of: a path | |
1184 | argument — in which case the specified path will be mounted from the host to the same path in the container, or | |
1185 | a colon-separated pair of paths — in which case the first specified path is the source in the host, and the | |
1186 | second path is the destination in the container, or a colon-separated triple of source path, destination path | |
1187 | and mount options. The source path may optionally be prefixed with a <literal>+</literal> character. If so, the | |
1188 | source path is taken relative to the image's root directory. This permits setting up bind mounts within the | |
1189 | container image. The source path may be specified as empty string, in which case a temporary directory below | |
1190 | the host's <filename>/var/tmp</filename> directory is used. It is automatically removed when the container is | |
1191 | shut down. Mount options are comma-separated and currently, only <option>rbind</option> and | |
1192 | <option>norbind</option> are allowed, controlling whether to create a recursive or a regular bind | |
1193 | mount. Defaults to "rbind". Backslash escapes are interpreted, so <literal>\:</literal> may be used to embed | |
1194 | colons in either path. This option may be specified multiple times for creating multiple independent bind | |
1195 | mount points. The <option>--bind-ro=</option> option creates read-only bind mounts.</para> | |
1196 | ||
1197 | <para>Note that when this option is used in combination with <option>--private-users</option>, the resulting | |
1198 | mount points will be owned by the <constant>nobody</constant> user. That's because the mount and its files and | |
1199 | directories continue to be owned by the relevant host users and groups, which do not exist in the container, | |
1200 | and thus show up under the wildcard UID 65534 (nobody). If such bind mounts are created, it is recommended to | |
1201 | make them read-only, using <option>--bind-ro=</option>.</para></listitem> | |
1202 | </varlistentry> | |
1203 | ||
1204 | <varlistentry> | |
1205 | <term><option>--inaccessible=</option></term> | |
1206 | ||
1207 | <listitem><para>Make the specified path inaccessible in the container. This over-mounts the specified path | |
1208 | (which must exist in the container) with a file node of the same type that is empty and has the most | |
1209 | restrictive access mode supported. This is an effective way to mask files, directories and other file system | |
1210 | objects from the container payload. This option may be used more than once in case all specified paths are | |
1211 | masked.</para></listitem> | |
1212 | </varlistentry> | |
1213 | ||
1214 | <varlistentry> | |
1215 | <term><option>--tmpfs=</option></term> | |
1216 | ||
1217 | <listitem><para>Mount a tmpfs file system into the container. Takes a single absolute path argument that | |
1218 | specifies where to mount the tmpfs instance to (in which case the directory access mode will be chosen as 0755, | |
1219 | owned by root/root), or optionally a colon-separated pair of path and mount option string that is used for | |
1220 | mounting (in which case the kernel default for access mode and owner will be chosen, unless otherwise | |
1221 | specified). Backslash escapes are interpreted in the path, so <literal>\:</literal> may be used to embed colons | |
1222 | in the path.</para> | |
1223 | ||
1224 | <para>Note that this option cannot be used to replace the root file system of the container with a temporary | |
1225 | file system. However, the <option>--volatile=</option> option described below provides similar | |
1226 | functionality, with a focus on implementing stateless operating system images.</para></listitem> | |
1227 | </varlistentry> | |
1228 | ||
1229 | <varlistentry> | |
1230 | <term><option>--overlay=</option></term> | |
1231 | <term><option>--overlay-ro=</option></term> | |
1232 | ||
1233 | <listitem><para>Combine multiple directory trees into one | |
1234 | overlay file system and mount it into the container. Takes a | |
1235 | list of colon-separated paths to the directory trees to | |
1236 | combine and the destination mount point.</para> | |
1237 | ||
1238 | <para>Backslash escapes are interpreted in the paths, so | |
1239 | <literal>\:</literal> may be used to embed colons in the paths. | |
1240 | </para> | |
1241 | ||
1242 | <para>If three or more paths are specified, then the last | |
1243 | specified path is the destination mount point in the | |
1244 | container, all paths specified before refer to directory trees | |
1245 | on the host and are combined in the specified order into one | |
1246 | overlay file system. The left-most path is hence the lowest | |
1247 | directory tree, the second-to-last path the highest directory | |
1248 | tree in the stacking order. If <option>--overlay-ro=</option> | |
1249 | is used instead of <option>--overlay=</option>, a read-only | |
1250 | overlay file system is created. If a writable overlay file | |
1251 | system is created, all changes made to it are written to the | |
1252 | highest directory tree in the stacking order, i.e. the | |
1253 | second-to-last specified.</para> | |
1254 | ||
1255 | <para>If only two paths are specified, then the second | |
1256 | specified path is used both as the top-level directory tree in | |
1257 | the stacking order as seen from the host, as well as the mount | |
1258 | point for the overlay file system in the container. At least | |
1259 | two paths have to be specified.</para> | |
1260 | ||
1261 | <para>The source paths may optionally be prefixed with <literal>+</literal> character. If so they are taken | |
1262 | relative to the image's root directory. The uppermost source path may also be specified as empty string, in | |
1263 | which case a temporary directory below the host's <filename>/var/tmp</filename> is used. The directory is | |
1264 | removed automatically when the container is shut down. This behaviour is useful in order to make read-only | |
1265 | container directories writable while the container is running. For example, use the | |
1266 | <literal>--overlay=+/var::/var</literal> option in order to automatically overlay a writable temporary | |
1267 | directory on a read-only <filename>/var</filename> directory.</para> | |
1268 | ||
1269 | <para>For details about overlay file systems, see <ulink | |
1270 | url="https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt">overlayfs.txt</ulink>. Note | |
1271 | that the semantics of overlay file systems are substantially | |
1272 | different from normal file systems, in particular regarding | |
1273 | reported device and inode information. Device and inode | |
1274 | information may change for a file while it is being written | |
1275 | to, and processes might see out-of-date versions of files at | |
1276 | times. Note that this switch automatically derives the | |
1277 | <literal>workdir=</literal> mount option for the overlay file | |
1278 | system from the top-level directory tree, making it a sibling | |
1279 | of it. It is hence essential that the top-level directory tree | |
1280 | is not a mount point itself (since the working directory must | |
1281 | be on the same file system as the top-most directory | |
1282 | tree). Also note that the <literal>lowerdir=</literal> mount | |
1283 | option receives the paths to stack in the opposite order of | |
1284 | this switch.</para> | |
1285 | ||
1286 | <para>Note that this option cannot be used to replace the root file system of the container with an overlay | |
1287 | file system. However, the <option>--volatile=</option> option described above provides similar functionality, | |
1288 | with a focus on implementing stateless operating system images.</para></listitem> | |
1289 | </varlistentry> | |
1290 | </variablelist> | |
1291 | ||
1292 | </refsect2><refsect2> | |
1293 | <title>Input/Output Options</title> | |
1294 | ||
1295 | <variablelist> | |
1296 | <varlistentry> | |
1297 | <term><option>--console=</option><replaceable>MODE</replaceable></term> | |
1298 | ||
1299 | <listitem><para>Configures how to set up standard input, output and error output for the container | |
1300 | payload, as well as the <filename>/dev/console</filename> device for the container. Takes one of | |
1301 | <option>interactive</option>, <option>read-only</option>, <option>passive</option>, or | |
1302 | <option>pipe</option>. If <option>interactive</option>, a pseudo-TTY is allocated and made available | |
1303 | as <filename>/dev/console</filename> in the container. It is then bi-directionally connected to the | |
1304 | standard input and output passed to <command>systemd-nspawn</command>. <option>read-only</option> is | |
1305 | similar but only the output of the container is propagated and no input from the caller is read. If | |
1306 | <option>passive</option>, a pseudo TTY is allocated, but it is not connected anywhere. Finally, in | |
1307 | <option>pipe</option> mode no pseudo TTY is allocated, but the standard input, output and error | |
1308 | output file descriptors passed to <command>systemd-nspawn</command> are passed on — as they are — to | |
1309 | the container payload, see the following paragraph. Defaults to <option>interactive</option> if | |
1310 | <command>systemd-nspawn</command> is invoked from a terminal, and <option>read-only</option> | |
1311 | otherwise.</para> | |
1312 | ||
1313 | <para>In <option>pipe</option> mode, <filename>/dev/console</filename> will not exist in the | |
1314 | container. This means that the container payload generally cannot be a full init system as init | |
1315 | systems tend to require <filename>/dev/console</filename> to be available. On the other hand, in this | |
1316 | mode container invocations can be used within shell pipelines. This is because intermediary pseudo | |
1317 | TTYs do not permit independent bidirectional propagation of the end-of-file (EOF) condition, which is | |
1318 | necessary for shell pipelines to work correctly. <emphasis>Note that the <option>pipe</option> mode | |
1319 | should be used carefully</emphasis>, as passing arbitrary file descriptors to less trusted container | |
1320 | payloads might open up unwanted interfaces for access by the container payload. For example, if a | |
1321 | passed file descriptor refers to a TTY of some form, APIs such as <constant>TIOCSTI</constant> may be | |
1322 | used to synthesize input that might be used for escaping the container. Hence <option>pipe</option> | |
1323 | mode should only be used if the payload is sufficiently trusted or when the standard | |
1324 | input/output/error output file descriptors are known safe, for example pipes.</para></listitem> | |
1325 | </varlistentry> | |
1326 | ||
1327 | <varlistentry> | |
1328 | <term><option>--pipe</option></term> | |
1329 | <term><option>-P</option></term> | |
1330 | ||
1331 | <listitem><para>Equivalent to <option>--console=pipe</option>.</para></listitem> | |
1332 | </varlistentry> | |
1333 | ||
1334 | <xi:include href="standard-options.xml" xpointer="no-pager" /> | |
1335 | <xi:include href="standard-options.xml" xpointer="help" /> | |
1336 | <xi:include href="standard-options.xml" xpointer="version" /> | |
1337 | </variablelist> | |
1338 | </refsect2> | |
1339 | </refsect1> | |
1340 | ||
1341 | <xi:include href="less-variables.xml" /> | |
1342 | ||
1343 | <refsect1> | |
1344 | <title>Examples</title> | |
1345 | ||
1346 | <example> | |
1347 | <title>Download a | |
1348 | <ulink url="https://getfedora.org">Fedora</ulink> image and start a shell in it</title> | |
1349 | ||
1350 | <programlisting># machinectl pull-raw --verify=no \ | |
1351 | https://download.fedoraproject.org/pub/fedora/linux/releases/&fedora_latest_version;/Cloud/x86_64/images/Fedora-Cloud-Base-&fedora_latest_version;-&fedora_cloud_release;.x86_64.raw.xz \ | |
1352 | Fedora-Cloud-Base-&fedora_latest_version;-&fedora_cloud_release;.x86-64 | |
1353 | # systemd-nspawn -M Fedora-Cloud-Base-&fedora_latest_version;-&fedora_cloud_release;.x86-64</programlisting> | |
1354 | ||
1355 | <para>This downloads an image using | |
1356 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
1357 | and opens a shell in it.</para> | |
1358 | </example> | |
1359 | ||
1360 | <example> | |
1361 | <title>Build and boot a minimal Fedora distribution in a container</title> | |
1362 | ||
1363 | <programlisting># dnf -y --releasever=&fedora_latest_version; --installroot=/var/lib/machines/f&fedora_latest_version; \ | |
1364 | --disablerepo='*' --enablerepo=fedora --enablerepo=updates install \ | |
1365 | systemd passwd dnf fedora-release vim-minimal | |
1366 | # systemd-nspawn -bD /var/lib/machines/f&fedora_latest_version;</programlisting> | |
1367 | ||
1368 | <para>This installs a minimal Fedora distribution into the | |
1369 | directory <filename index="false">/var/lib/machines/f&fedora_latest_version;</filename> | |
1370 | and then boots an OS in a namespace container in it. Because the installation | |
1371 | is located underneath the standard <filename>/var/lib/machines/</filename> | |
1372 | directory, it is also possible to start the machine using | |
1373 | <command>systemd-nspawn -M f&fedora_latest_version;</command>.</para> | |
1374 | </example> | |
1375 | ||
1376 | <example> | |
1377 | <title>Spawn a shell in a container of a minimal Debian unstable distribution</title> | |
1378 | ||
1379 | <programlisting># debootstrap unstable ~/debian-tree/ | |
1380 | # systemd-nspawn -D ~/debian-tree/</programlisting> | |
1381 | ||
1382 | <para>This installs a minimal Debian unstable distribution into | |
1383 | the directory <filename>~/debian-tree/</filename> and then | |
1384 | spawns a shell in a namespace container in it.</para> | |
1385 | ||
1386 | <para><command>debootstrap</command> supports | |
1387 | <ulink url="https://www.debian.org">Debian</ulink>, | |
1388 | <ulink url="https://www.ubuntu.com">Ubuntu</ulink>, | |
1389 | and <ulink url="https://www.tanglu.org">Tanglu</ulink> | |
1390 | out of the box, so the same command can be used to install any of those. For other | |
1391 | distributions from the Debian family, a mirror has to be specified, see | |
1392 | <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
1393 | </para> | |
1394 | </example> | |
1395 | ||
1396 | <example> | |
1397 | <title>Boot a minimal | |
1398 | <ulink url="https://www.archlinux.org">Arch Linux</ulink> distribution in a container</title> | |
1399 | ||
1400 | <programlisting># pacstrap -c ~/arch-tree/ base | |
1401 | # systemd-nspawn -bD ~/arch-tree/</programlisting> | |
1402 | ||
1403 | <para>This installs a minimal Arch Linux distribution into the | |
1404 | directory <filename>~/arch-tree/</filename> and then boots an OS | |
1405 | in a namespace container in it.</para> | |
1406 | </example> | |
1407 | ||
1408 | <example> | |
1409 | <title>Install the | |
1410 | <ulink url="https://software.opensuse.org/distributions/tumbleweed">OpenSUSE Tumbleweed</ulink> | |
1411 | rolling distribution</title> | |
1412 | ||
1413 | <programlisting># zypper --root=/var/lib/machines/tumbleweed ar -c \ | |
1414 | https://download.opensuse.org/tumbleweed/repo/oss tumbleweed | |
1415 | # zypper --root=/var/lib/machines/tumbleweed refresh | |
1416 | # zypper --root=/var/lib/machines/tumbleweed install --no-recommends \ | |
1417 | systemd shadow zypper openSUSE-release vim | |
1418 | # systemd-nspawn -M tumbleweed passwd root | |
1419 | # systemd-nspawn -M tumbleweed -b</programlisting> | |
1420 | </example> | |
1421 | ||
1422 | <example> | |
1423 | <title>Boot into an ephemeral snapshot of the host system</title> | |
1424 | ||
1425 | <programlisting># systemd-nspawn -D / -xb</programlisting> | |
1426 | ||
1427 | <para>This runs a copy of the host system in a snapshot which is removed immediately when the container | |
1428 | exits. All file system changes made during runtime will be lost on shutdown, hence.</para> | |
1429 | </example> | |
1430 | ||
1431 | <example> | |
1432 | <title>Run a container with SELinux sandbox security contexts</title> | |
1433 | ||
1434 | <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container | |
1435 | # systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 \ | |
1436 | -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh</programlisting> | |
1437 | </example> | |
1438 | ||
1439 | <example> | |
1440 | <title>Run a container with an OSTree deployment</title> | |
1441 | ||
1442 | <programlisting># systemd-nspawn -b -i ~/image.raw \ | |
1443 | --pivot-root=/ostree/deploy/$OS/deploy/$CHECKSUM:/sysroot \ | |
1444 | --bind=+/sysroot/ostree/deploy/$OS/var:/var</programlisting> | |
1445 | </example> | |
1446 | </refsect1> | |
1447 | ||
1448 | <refsect1> | |
1449 | <title>Exit status</title> | |
1450 | ||
1451 | <para>The exit code of the program executed in the container is | |
1452 | returned.</para> | |
1453 | </refsect1> | |
1454 | ||
1455 | <refsect1> | |
1456 | <title>See Also</title> | |
1457 | <para> | |
1458 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
1459 | <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
1460 | <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
1461 | <citerefentry project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
1462 | <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
1463 | <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
1464 | <citerefentry project='mankier'><refentrytitle>zypper</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
1465 | <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
1466 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
1467 | <citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
1468 | </para> | |
1469 | </refsect1> | |
1470 | ||
1471 | </refentry> |