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1 | <?xml version='1.0'?> <!--*-nxml-*--> | |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2010 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
19 | ||
20 | You should have received a copy of the GNU Lesser General Public License | |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
22 | --> | |
23 | ||
24 | <refentry id="systemd-nspawn"> | |
25 | ||
26 | <refentryinfo> | |
27 | <title>systemd-nspawn</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>systemd-nspawn</refentrytitle> | |
42 | <manvolnum>1</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>systemd-nspawn</refname> | |
47 | <refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose> | |
48 | </refnamediv> | |
49 | ||
50 | <refsynopsisdiv> | |
51 | <cmdsynopsis> | |
52 | <command>systemd-nspawn</command> | |
53 | <arg choice="opt" rep="repeat">OPTIONS</arg> | |
54 | <arg choice="opt"><replaceable>COMMAND</replaceable> | |
55 | <arg choice="opt" rep="repeat">ARGS</arg> | |
56 | </arg> | |
57 | </cmdsynopsis> | |
58 | <cmdsynopsis> | |
59 | <command>systemd-nspawn</command> | |
60 | <arg choice="plain">-b</arg> | |
61 | <arg choice="opt" rep="repeat">OPTIONS</arg> | |
62 | <arg choice="opt" rep="repeat">ARGS</arg> | |
63 | </cmdsynopsis> | |
64 | </refsynopsisdiv> | |
65 | ||
66 | <refsect1> | |
67 | <title>Description</title> | |
68 | ||
69 | <para><command>systemd-nspawn</command> may be used to | |
70 | run a command or OS in a light-weight namespace | |
71 | container. In many ways it is similar to | |
72 | <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
73 | but more powerful since it fully virtualizes the file | |
74 | system hierarchy, as well as the process tree, the | |
75 | various IPC subsystems and the host and domain | |
76 | name.</para> | |
77 | ||
78 | <para><command>systemd-nspawn</command> limits access | |
79 | to various kernel interfaces in the container to | |
80 | read-only, such as <filename>/sys</filename>, | |
81 | <filename>/proc/sys</filename> or | |
82 | <filename>/sys/fs/selinux</filename>. Network | |
83 | interfaces and the system clock may not be changed | |
84 | from within the container. Device nodes may not be | |
85 | created. The host system cannot be rebooted and kernel | |
86 | modules may not be loaded from within the | |
87 | container.</para> | |
88 | ||
89 | <para>Note that even though these security precautions | |
90 | are taken <command>systemd-nspawn</command> is not | |
91 | suitable for secure container setups. Many of the | |
92 | security features may be circumvented and are hence | |
93 | primarily useful to avoid accidental changes to the | |
94 | host system from the container. The intended use of | |
95 | this program is debugging and testing as well as | |
96 | building of packages, distributions and software | |
97 | involved with boot and systems management.</para> | |
98 | ||
99 | <para>In contrast to | |
100 | <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command> | |
101 | may be used to boot full Linux-based operating systems | |
102 | in a container.</para> | |
103 | ||
104 | <para>Use a tool like | |
105 | <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
106 | <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
107 | or | |
108 | <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
109 | to set up an OS directory tree suitable as file system | |
110 | hierarchy for <command>systemd-nspawn</command> | |
111 | containers.</para> | |
112 | ||
113 | <para>Note that <command>systemd-nspawn</command> will | |
114 | mount file systems private to the container to | |
115 | <filename>/dev</filename>, | |
116 | <filename>/run</filename> and similar. These will | |
117 | not be visible outside of the container, and their | |
118 | contents will be lost when the container exits.</para> | |
119 | ||
120 | <para>Note that running two | |
121 | <command>systemd-nspawn</command> containers from the | |
122 | same directory tree will not make processes in them | |
123 | see each other. The PID namespace separation of the | |
124 | two containers is complete and the containers will | |
125 | share very few runtime objects except for the | |
126 | underlying file system. It is however possible to | |
127 | enter an existing container, see | |
128 | <link linkend='example-nsenter'>Example 4</link> below. | |
129 | </para> | |
130 | ||
131 | <para><command>systemd-nspawn</command> implements the | |
132 | <ulink | |
133 | url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container | |
134 | Interface</ulink> specification.</para> | |
135 | ||
136 | <para>As a safety check | |
137 | <command>systemd-nspawn</command> will verify the | |
138 | existence of <filename>/etc/os-release</filename> in | |
139 | the container tree before starting the container (see | |
140 | <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It | |
141 | might be necessary to add this file to the container | |
142 | tree manually if the OS of the container is too old to | |
143 | contain this file out-of-the-box.</para> | |
144 | </refsect1> | |
145 | ||
146 | <refsect1> | |
147 | <title>Incompatibility with Auditing</title> | |
148 | ||
149 | <para>Note that the kernel auditing subsystem is | |
150 | currently broken when used together with | |
151 | containers. We hence recommend turning it off entirely | |
152 | by booting with <literal>audit=0</literal> on the | |
153 | kernel command line, or by turning it off at kernel | |
154 | build time. If auditing is enabled in the kernel | |
155 | operating systems booted in an nspawn container might | |
156 | refuse log-in attempts.</para> | |
157 | </refsect1> | |
158 | ||
159 | <refsect1> | |
160 | <title>Options</title> | |
161 | ||
162 | <para>If option <option>-b</option> is specified, the | |
163 | arguments are used as arguments for the init | |
164 | binary. Otherwise, <replaceable>COMMAND</replaceable> | |
165 | specifies the program to launch in the container, and | |
166 | the remaining arguments are used as arguments for this | |
167 | program. If <option>-b</option> is not used and no | |
168 | arguments are specifed, a shell is launched in the | |
169 | container.</para> | |
170 | ||
171 | <para>The following options are understood:</para> | |
172 | ||
173 | <variablelist> | |
174 | <varlistentry> | |
175 | <term><option>-h</option></term> | |
176 | <term><option>--help</option></term> | |
177 | ||
178 | <listitem><para>Prints a short help | |
179 | text and exits.</para></listitem> | |
180 | </varlistentry> | |
181 | ||
182 | <varlistentry> | |
183 | <term><option>--version</option></term> | |
184 | ||
185 | <listitem><para>Prints a version string | |
186 | and exits.</para></listitem> | |
187 | </varlistentry> | |
188 | ||
189 | <varlistentry> | |
190 | <term><option>-D</option></term> | |
191 | <term><option>--directory=</option></term> | |
192 | ||
193 | <listitem><para>Directory to use as | |
194 | file system root for the namespace | |
195 | container. If omitted the current | |
196 | directory will be | |
197 | used.</para></listitem> | |
198 | </varlistentry> | |
199 | ||
200 | <varlistentry> | |
201 | <term><option>-b</option></term> | |
202 | <term><option>--boot</option></term> | |
203 | ||
204 | <listitem><para>Automatically search | |
205 | for an init binary and invoke it | |
206 | instead of a shell or a user supplied | |
207 | program. If this option is used, arguments | |
208 | specified on the command line are used | |
209 | as arguments for the init binary. | |
210 | </para></listitem> | |
211 | </varlistentry> | |
212 | ||
213 | <varlistentry> | |
214 | <term><option>-u</option></term> | |
215 | <term><option>--user=</option></term> | |
216 | ||
217 | <listitem><para>Run the command | |
218 | under specified user, create home | |
219 | directory and cd into it. As rest | |
220 | of systemd-nspawn, this is not | |
221 | the security feature and limits | |
222 | against accidental changes only. | |
223 | </para></listitem> | |
224 | </varlistentry> | |
225 | ||
226 | <varlistentry> | |
227 | <term><option>-M</option></term> | |
228 | <term><option>--machine=</option></term> | |
229 | ||
230 | <listitem><para>Sets the machine name | |
231 | for this container. This name may be | |
232 | used to identify this container on the | |
233 | host, and is used to initialize the | |
234 | container's hostname (which the | |
235 | container can choose to override, | |
236 | however). If not specified the last | |
237 | component of the root directory of the | |
238 | container is used.</para></listitem> | |
239 | </varlistentry> | |
240 | ||
241 | <varlistentry> | |
242 | <term><option>--slice=</option></term> | |
243 | ||
244 | <listitem><para>Make the container | |
245 | part of the specified slice, instead | |
246 | of the | |
247 | <filename>machine.slice</filename>.</para> | |
248 | </listitem> | |
249 | </varlistentry> | |
250 | ||
251 | <varlistentry> | |
252 | <term><option>--uuid=</option></term> | |
253 | ||
254 | <listitem><para>Set the specified UUID | |
255 | for the container. The init system | |
256 | will initialize | |
257 | <filename>/etc/machine-id</filename> | |
258 | from this if this file is not set yet. | |
259 | </para></listitem> | |
260 | </varlistentry> | |
261 | ||
262 | <varlistentry> | |
263 | <term><option>--private-network</option></term> | |
264 | ||
265 | <listitem><para>Turn off networking in | |
266 | the container. This makes all network | |
267 | interfaces unavailable in the | |
268 | container, with the exception of the | |
269 | loopback device.</para></listitem> | |
270 | </varlistentry> | |
271 | ||
272 | <varlistentry> | |
273 | <term><option>--read-only</option></term> | |
274 | ||
275 | <listitem><para>Mount the root file | |
276 | system read-only for the | |
277 | container.</para></listitem> | |
278 | </varlistentry> | |
279 | ||
280 | <varlistentry> | |
281 | <term><option>--capability=</option></term> | |
282 | ||
283 | <listitem><para>List one or more | |
284 | additional capabilities to grant the | |
285 | container. Takes a comma-separated | |
286 | list of capability names, see | |
287 | <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
288 | for more information. Note that the | |
289 | following capabilities will be granted | |
290 | in any way: CAP_CHOWN, | |
291 | CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, | |
292 | CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER, | |
293 | CAP_KILL, CAP_LEASE, | |
294 | CAP_LINUX_IMMUTABLE, | |
295 | CAP_NET_BIND_SERVICE, | |
296 | CAP_NET_BROADCAST, CAP_NET_RAW, | |
297 | CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP, | |
298 | CAP_SETUID, CAP_SYS_ADMIN, | |
299 | CAP_SYS_CHROOT, CAP_SYS_NICE, | |
300 | CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG, | |
301 | CAP_SYS_RESOURCE, CAP_SYS_BOOT, | |
302 | CAP_AUDIT_WRITE, | |
303 | CAP_AUDIT_CONTROL.</para></listitem> | |
304 | </varlistentry> | |
305 | ||
306 | <varlistentry> | |
307 | <term><option>--link-journal=</option></term> | |
308 | ||
309 | <listitem><para>Control whether the | |
310 | container's journal shall be made | |
311 | visible to the host system. If enabled | |
312 | allows viewing the container's journal | |
313 | files from the host (but not vice | |
314 | versa). Takes one of | |
315 | <literal>no</literal>, | |
316 | <literal>host</literal>, | |
317 | <literal>guest</literal>, | |
318 | <literal>auto</literal>. If | |
319 | <literal>no</literal>, the journal is | |
320 | not linked. If <literal>host</literal>, | |
321 | the journal files are stored on the | |
322 | host file system (beneath | |
323 | <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>) | |
324 | and the subdirectory is bind-mounted | |
325 | into the container at the same | |
326 | location. If <literal>guest</literal>, | |
327 | the journal files are stored on the | |
328 | guest file system (beneath | |
329 | <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>) | |
330 | and the subdirectory is symlinked into the host | |
331 | at the same location. If | |
332 | <literal>auto</literal> (the default), | |
333 | and the right subdirectory of | |
334 | <filename>/var/log/journal</filename> | |
335 | exists, it will be bind mounted | |
336 | into the container. If the | |
337 | subdirectory doesn't exist, no | |
338 | linking is performed. Effectively, | |
339 | booting a container once with | |
340 | <literal>guest</literal> or | |
341 | <literal>host</literal> will link the | |
342 | journal persistently if further on | |
343 | the default of <literal>auto</literal> | |
344 | is used.</para></listitem> | |
345 | </varlistentry> | |
346 | ||
347 | <varlistentry> | |
348 | <term><option>-j</option></term> | |
349 | ||
350 | <listitem><para>Equivalent to | |
351 | <option>--link-journal=guest</option>.</para></listitem> | |
352 | </varlistentry> | |
353 | ||
354 | <varlistentry> | |
355 | <term><option>--bind=</option></term> | |
356 | <term><option>--bind-ro=</option></term> | |
357 | ||
358 | <listitem><para>Bind mount a file or | |
359 | directory from the host into the | |
360 | container. Either takes a path | |
361 | argument -- in which case the | |
362 | specified path will be mounted from | |
363 | the host to the same path in the | |
364 | container --, or a colon-separated | |
365 | pair of paths -- in which case the | |
366 | first specified path is the source in | |
367 | the host, and the second path is the | |
368 | destination in the container. The | |
369 | <option>--bind-ro=</option> option | |
370 | creates read-only bind | |
371 | mount.</para></listitem> | |
372 | </varlistentry> | |
373 | </variablelist> | |
374 | ||
375 | </refsect1> | |
376 | ||
377 | <refsect1> | |
378 | <title>Example 1</title> | |
379 | ||
380 | <programlisting># yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal | |
381 | # systemd-nspawn -bD /srv/mycontainer</programlisting> | |
382 | ||
383 | <para>This installs a minimal Fedora distribution into | |
384 | the directory <filename noindex='true'>/srv/mycontainer/</filename> and | |
385 | then boots an OS in a namespace container in | |
386 | it.</para> | |
387 | </refsect1> | |
388 | ||
389 | <refsect1> | |
390 | <title>Example 2</title> | |
391 | ||
392 | <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/ | |
393 | # systemd-nspawn -D ~/debian-tree/</programlisting> | |
394 | ||
395 | <para>This installs a minimal Debian unstable | |
396 | distribution into the directory | |
397 | <filename>~/debian-tree/</filename> and then spawns a | |
398 | shell in a namespace container in it.</para> | |
399 | </refsect1> | |
400 | ||
401 | <refsect1> | |
402 | <title>Example 3</title> | |
403 | ||
404 | <programlisting># pacstrap -c -d ~/arch-tree/ base | |
405 | # systemd-nspawn -bD ~/arch-tree/</programlisting> | |
406 | ||
407 | <para>This installs a mimimal Arch Linux distribution into | |
408 | the directory <filename>~/arch-tree/</filename> and then | |
409 | boots an OS in a namespace container in it.</para> | |
410 | </refsect1> | |
411 | ||
412 | <refsect1 id='example-nsenter'> | |
413 | <title>Example 4</title> | |
414 | ||
415 | <para>To enter the container, PID of one of the | |
416 | processes sharing the new namespaces must be used. | |
417 | <command>systemd-nspawn</command> prints the PID | |
418 | (as viewed from the outside) of the launched process, | |
419 | and it can be used to enter the container.</para> | |
420 | ||
421 | <programlisting># nsenter -m -u -i -n -p -t $PID</programlisting> | |
422 | ||
423 | <para><citerefentry><refentrytitle>nsenter</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
424 | is part of | |
425 | <ulink url="https://github.com/karelzak/util-linux">util-linux</ulink>. | |
426 | Kernel support for entering namespaces was added in | |
427 | Linux 3.8.</para> | |
428 | </refsect1> | |
429 | ||
430 | <refsect1> | |
431 | <title>Exit status</title> | |
432 | ||
433 | <para>The exit code of the program executed in the | |
434 | container is returned.</para> | |
435 | </refsect1> | |
436 | ||
437 | <refsect1> | |
438 | <title>See Also</title> | |
439 | <para> | |
440 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
441 | <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
442 | <citerefentry><refentrytitle>unshare</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
443 | <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
444 | <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
445 | <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
446 | <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
447 | </para> | |
448 | </refsect1> | |
449 | ||
450 | </refentry> |