man/systemd-nspawn.xml

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  23
  24 <refentry id="systemd-nspawn"
  25     xmlns:xi="http://www.w3.org/2001/XInclude">
  26
  27   <refentryinfo>
  28     <title>systemd-nspawn</title>
  29     <productname>systemd</productname>
  30
  31     <authorgroup>
  32       <author>
  33         <contrib>Developer</contrib>
  34         <firstname>Lennart</firstname>
  35         <surname>Poettering</surname>
  36         <email>lennart@poettering.net</email>
  37       </author>
  38     </authorgroup>
  39   </refentryinfo>
  40
  41   <refmeta>
  42     <refentrytitle>systemd-nspawn</refentrytitle>
  43     <manvolnum>1</manvolnum>
  44   </refmeta>
  45
  46   <refnamediv>
  47     <refname>systemd-nspawn</refname>
  48     <refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose>
  49   </refnamediv>
  50
  51   <refsynopsisdiv>
  52     <cmdsynopsis>
  53       <command>systemd-nspawn</command>
  54       <arg choice="opt" rep="repeat">OPTIONS</arg>
  55       <arg choice="opt"><replaceable>COMMAND</replaceable>
  56       <arg choice="opt" rep="repeat">ARGS</arg>
  57       </arg>
  58     </cmdsynopsis>
  59     <cmdsynopsis>
  60       <command>systemd-nspawn</command>
  61       <arg choice="plain">--boot</arg>
  62       <arg choice="opt" rep="repeat">OPTIONS</arg>
  63       <arg choice="opt" rep="repeat">ARGS</arg>
  64     </cmdsynopsis>
  65   </refsynopsisdiv>
  66
  67   <refsect1>
  68     <title>Description</title>
  69
  70     <para><command>systemd-nspawn</command> may be used to run a command or OS in a light-weight namespace
  71     container. In many ways it is similar to <citerefentry
  72     project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>, but more powerful
  73     since it fully virtualizes the file system hierarchy, as well as the process tree, the various IPC subsystems and
  74     the host and domain name.</para>
  75
  76     <para><command>systemd-nspawn</command> may be invoked on any directory tree containing an operating system tree,
  77     using the <option>--directory=</option> command line option. By using the <option>--machine=</option> option an OS
  78     tree is automatically searched for in a couple of locations, most importantly in
  79     <filename>/var/lib/machines</filename>, the suggested directory to place container images installed on the
  80     system.</para>
  81
  82     <para>In contrast to <citerefentry
  83     project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command>
  84     may be used to boot full Linux-based operating systems in a container.</para>
  85
  86     <para><command>systemd-nspawn</command> limits access to various kernel interfaces in the container to read-only,
  87     such as <filename>/sys</filename>, <filename>/proc/sys</filename> or <filename>/sys/fs/selinux</filename>. The
  88     host's network interfaces and the system clock may not be changed from within the container. Device nodes may not
  89     be created. The host system cannot be rebooted and kernel modules may not be loaded from within the
  90     container.</para>
  91
  92     <para>Use a tool like <citerefentry
  93     project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry
  94     project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or
  95     <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry> to
  96     set up an OS directory tree suitable as file system hierarchy for <command>systemd-nspawn</command> containers. See
  97     the Examples section below for details on suitable invocation of these commands.</para>
  98
  99     <para>As a safety check <command>systemd-nspawn</command> will verify the existence of
 100     <filename>/usr/lib/os-release</filename> or <filename>/etc/os-release</filename> in the container tree before
 101     starting the container (see
 102     <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>).  It might be
 103     necessary to add this file to the container tree manually if the OS of the container is too old to contain this
 104     file out-of-the-box.</para>
 105
 106     <para><command>systemd-nspawn</command> may be invoked directly from the interactive command line or run as system
 107     service in the background. In this mode each container instance runs as its own service instance; a default
 108     template unit file <filename>systemd-nspawn@.service</filename> is provided to make this easy, taking the container
 109     name as instance identifier. Note that different default options apply when <command>systemd-nspawn</command> is
 110     invoked by the template unit file than interactively on the command line. Most importantly the template unit file
 111     makes use of the <option>--boot</option> which is not the default in case <command>systemd-nspawn</command> is
 112     invoked from the interactive command line. Further differences with the defaults are documented along with the
 113     various supported options below.</para>
 114
 115     <para>The <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool may
 116     be used to execute a number of operations on containers. In particular it provides easy-to-use commands to run
 117     containers as system services using the <filename>systemd-nspawn@.service</filename> template unit
 118     file.</para>
 119
 120     <para>Along with each container a settings file with the <filename>.nspawn</filename> suffix may exist, containing
 121     additional settings to apply when running the container. See
 122     <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 123     details. Settings files override the default options used by the <filename>systemd-nspawn@.service</filename>
 124     template unit file, making it usually unnecessary to alter this template file directly.</para>
 125
 126     <para>Note that <command>systemd-nspawn</command> will mount file systems private to the container to
 127     <filename>/dev</filename>, <filename>/run</filename> and similar. These will not be visible outside of the
 128     container, and their contents will be lost when the container exits.</para>
 129
 130     <para>Note that running two <command>systemd-nspawn</command> containers from the same directory tree will not make
 131     processes in them see each other. The PID namespace separation of the two containers is complete and the containers
 132     will share very few runtime objects except for the underlying file system. Use
 133     <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 134     <command>login</command> or <command>shell</command> commands to request an additional login session in a running
 135     container.</para>
 136
 137     <para><command>systemd-nspawn</command> implements the <ulink
 138     url="https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container Interface</ulink>
 139     specification.</para>
 140
 141     <para>While running, containers invoked with <command>systemd-nspawn</command> are registered with the
 142     <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> service that
 143     keeps track of running containers, and provides programming interfaces to interact with them.</para>
 144   </refsect1>
 145
 146   <refsect1>
 147     <title>Options</title>
 148
 149     <para>If option <option>-b</option> is specified, the arguments
 150     are used as arguments for the init binary. Otherwise,
 151     <replaceable>COMMAND</replaceable> specifies the program to launch
 152     in the container, and the remaining arguments are used as
 153     arguments for this program. If <option>--boot</option> is not used and
 154     no arguments are specified, a shell is launched in the
 155     container.</para>
 156
 157     <para>The following options are understood:</para>
 158
 159     <variablelist>
 160       <varlistentry>
 161         <term><option>-D</option></term>
 162         <term><option>--directory=</option></term>
 163
 164         <listitem><para>Directory to use as file system root for the
 165         container.</para>
 166
 167         <para>If neither <option>--directory=</option>, nor
 168         <option>--image=</option> is specified the directory is
 169         determined by searching for a directory named the same as the
 170         machine name specified with <option>--machine=</option>. See
 171         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 172         section "Files and Directories" for the precise search path.</para>
 173
 174         <para>If neither <option>--directory=</option>,
 175         <option>--image=</option>, nor <option>--machine=</option>
 176         are specified, the current directory will
 177         be used. May not be specified together with
 178         <option>--image=</option>.</para></listitem>
 179       </varlistentry>
 180
 181       <varlistentry>
 182         <term><option>--template=</option></term>
 183
 184         <listitem><para>Directory or <literal>btrfs</literal> subvolume to use as template for the container's root
 185         directory. If this is specified and the container's root directory (as configured by
 186         <option>--directory=</option>) does not yet exist it is created as <literal>btrfs</literal> snapshot (if
 187         supported) or plain directory (otherwise) and populated from this template tree. Ideally, the specified
 188         template path refers to the root of a <literal>btrfs</literal> subvolume, in which case a simple copy-on-write
 189         snapshot is taken, and populating the root directory is instant. If the specified template path does not refer
 190         to the root of a <literal>btrfs</literal> subvolume (or not even to a <literal>btrfs</literal> file system at
 191         all), the tree is copied (though possibly in a copy-on-write scheme — if the file system supports that), which
 192         can be substantially more time-consuming. May not be specified together with <option>--image=</option> or
 193         <option>--ephemeral</option>.</para>
 194
 195         <para>Note that this switch leaves host name, machine ID and
 196         all other settings that could identify the instance
 197         unmodified.</para></listitem>
 198       </varlistentry>
 199
 200       <varlistentry>
 201         <term><option>-x</option></term>
 202         <term><option>--ephemeral</option></term>
 203
 204         <listitem><para>If specified, the container is run with a temporary snapshot of its file system that is removed
 205         immediately when the container terminates. May not be specified together with
 206         <option>--template=</option>.</para>
 207         <para>Note that this switch leaves host name, machine ID and
 208         all other settings that could identify the instance
 209         unmodified.</para></listitem>
 210       </varlistentry>
 211
 212       <varlistentry>
 213         <term><option>-i</option></term>
 214         <term><option>--image=</option></term>
 215
 216         <listitem><para>Disk image to mount the root directory for the
 217         container from. Takes a path to a regular file or to a block
 218         device node. The file or block device must contain
 219         either:</para>
 220
 221         <itemizedlist>
 222           <listitem><para>An MBR partition table with a single
 223           partition of type 0x83 that is marked
 224           bootable.</para></listitem>
 225
 226           <listitem><para>A GUID partition table (GPT) with a single
 227           partition of type
 228           0fc63daf-8483-4772-8e79-3d69d8477de4.</para></listitem>
 229
 230           <listitem><para>A GUID partition table (GPT) with a marked
 231           root partition which is mounted as the root directory of the
 232           container. Optionally, GPT images may contain a home and/or
 233           a server data partition which are mounted to the appropriate
 234           places in the container. All these partitions must be
 235           identified by the partition types defined by the <ulink
 236           url="https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
 237           Partitions Specification</ulink>.</para></listitem>
 238
 239           <listitem><para>No partition table, and a single file system spanning the whole image.</para></listitem>
 240         </itemizedlist>
 241
 242         <para>On GPT images, if an EFI System Partition (ESP) is discovered, it is automatically mounted to
 243         <filename>/efi</filename> (or <filename>/boot</filename> as fallback) in case a directory by this name exists
 244         and is empty.</para>
 245
 246         <para>Partitions encrypted with LUKS are automatically decrypted. Also, on GPT images dm-verity data integrity
 247         hash partitions are set up if the root hash for them is specified using the <option>--root-hash=</option>
 248         option.</para>
 249
 250         <para>Any other partitions, such as foreign partitions or swap partitions are not mounted. May not be specified
 251         together with <option>--directory=</option>, <option>--template=</option>.</para></listitem>
 252       </varlistentry>
 253
 254       <varlistentry>
 255         <term><option>--root-hash=</option></term>
 256
 257         <listitem><para>Takes a data integrity (dm-verity) root hash specified in hexadecimal. This option enables data
 258         integrity checks using dm-verity, if the used image contains the appropriate integrity data (see above). The
 259         specified hash must match the root hash of integrity data, and is usually at least 256 bits (and hence 64
 260         formatted hexadecimal characters) long (in case of SHA256 for example). If this option is not specified, but
 261         the image file carries the <literal>user.verity.roothash</literal> extended file attribute (see <citerefentry
 262         project='man-pages'><refentrytitle>xattr</refentrytitle><manvolnum>7</manvolnum></citerefentry>), then the root
 263         hash is read from it, also as formatted hexadecimal characters. If the extended file attribute is not found (or
 264         is not supported by the underlying file system), but a file with the <filename>.roothash</filename> suffix is
 265         found next to the image file, bearing otherwise the same name, the root hash is read from it and automatically
 266         used, also as formatted hexadecimal characters.</para></listitem>
 267       </varlistentry>
 268
 269       <varlistentry>
 270         <term><option>-a</option></term>
 271         <term><option>--as-pid2</option></term>
 272
 273         <listitem><para>Invoke the shell or specified program as process ID (PID) 2 instead of PID 1 (init). By
 274         default, if neither this option nor <option>--boot</option> is used, the selected binary is run as process with
 275         PID 1, a mode only suitable for programs that are aware of the special semantics that the process with PID 1
 276         has on UNIX. For example, it needs to reap all processes reparented to it, and should implement
 277         <command>sysvinit</command> compatible signal handling (specifically: it needs to reboot on SIGINT, reexecute
 278         on SIGTERM, reload configuration on SIGHUP, and so on). With <option>--as-pid2</option> a minimal stub init
 279         process is run as PID 1 and the selected binary is executed as PID 2 (and hence does not need to implement any
 280         special semantics). The stub init process will reap processes as necessary and react appropriately to
 281         signals. It is recommended to use this mode to invoke arbitrary commands in containers, unless they have been
 282         modified to run correctly as PID 1. Or in other words: this switch should be used for pretty much all commands,
 283         except when the command refers to an init or shell implementation, as these are generally capable of running
 284         correctly as PID 1. This option may not be combined with <option>--boot</option>.</para>
 285         </listitem>
 286       </varlistentry>
 287
 288       <varlistentry>
 289         <term><option>-b</option></term>
 290         <term><option>--boot</option></term>
 291
 292         <listitem><para>Automatically search for an init binary and invoke it as PID 1, instead of a shell or a user
 293         supplied program. If this option is used, arguments specified on the command line are used as arguments for the
 294         init binary. This option may not be combined with <option>--as-pid2</option>.</para>
 295
 296         <para>The following table explains the different modes of invocation and relationship to
 297         <option>--as-pid2</option> (see above):</para>
 298
 299         <table>
 300           <title>Invocation Mode</title>
 301           <tgroup cols='2' align='left' colsep='1' rowsep='1'>
 302             <colspec colname="switch" />
 303             <colspec colname="explanation" />
 304             <thead>
 305               <row>
 306                 <entry>Switch</entry>
 307                 <entry>Explanation</entry>
 308               </row>
 309             </thead>
 310             <tbody>
 311               <row>
 312                 <entry>Neither <option>--as-pid2</option> nor <option>--boot</option> specified</entry>
 313                 <entry>The passed parameters are interpreted as the command line, which is executed as PID 1 in the container.</entry>
 314               </row>
 315
 316               <row>
 317                 <entry><option>--as-pid2</option> specified</entry>
 318                 <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>
 319               </row>
 320
 321               <row>
 322                 <entry><option>--boot</option> specified</entry>
 323                 <entry>An init binary as automatically searched and run as PID 1 in the container. The passed parameters are used as invocation parameters for this process.</entry>
 324               </row>
 325
 326             </tbody>
 327           </tgroup>
 328         </table>
 329
 330         <para>Note that <option>--boot</option> is the default mode of operation if the
 331         <filename>systemd-nspawn@.service</filename> template unit file is used.</para>
 332         </listitem>
 333       </varlistentry>
 334
 335       <varlistentry>
 336         <term><option>--chdir=</option></term>
 337
 338         <listitem><para>Change to the specified working directory before invoking the process in the container. Expects
 339         an absolute path in the container's file system namespace.</para></listitem>
 340       </varlistentry>
 341
 342       <varlistentry>
 343         <term><option>--pivot-root=</option></term>
 344
 345         <listitem><para>Pivot the specified directory to <filename>/</filename> inside the container, and either unmount the
 346         container's old root, or pivot it to another specified directory. Takes one of: a path argument — in which case the
 347         specified path will be pivoted to <filename>/</filename> and the old root will be unmounted; or a colon-separated pair
 348         of new root path and pivot destination for the old root. The new root path will be pivoted to <filename>/</filename>,
 349         and the old <filename>/</filename> will be pivoted to the other directory. Both paths must be absolute, and are resolved
 350         in the container's file system namespace.</para>
 351
 352         <para>This is for containers which have several bootable directories in them; for example, several
 353         <ulink url="https://ostree.readthedocs.io/en/latest/">OSTree</ulink> deployments. It emulates the behavior of
 354         the boot loader and initial RAM disk which normally select which directory to mount as the root and start the
 355         container's PID 1 in.</para></listitem>
 356       </varlistentry>
 357
 358       <varlistentry>
 359         <term><option>-u</option></term>
 360         <term><option>--user=</option></term>
 361
 362         <listitem><para>After transitioning into the container, change
 363         to the specified user-defined in the container's user
 364         database. Like all other systemd-nspawn features, this is not
 365         a security feature and provides protection against accidental
 366         destructive operations only.</para></listitem>
 367       </varlistentry>
 368
 369       <varlistentry>
 370         <term><option>-M</option></term>
 371         <term><option>--machine=</option></term>
 372
 373         <listitem><para>Sets the machine name for this container. This
 374         name may be used to identify this container during its runtime
 375         (for example in tools like
 376         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 377         and similar), and is used to initialize the container's
 378         hostname (which the container can choose to override,
 379         however). If not specified, the last component of the root
 380         directory path of the container is used, possibly suffixed
 381         with a random identifier in case <option>--ephemeral</option>
 382         mode is selected. If the root directory selected is the host's
 383         root directory the host's hostname is used as default
 384         instead.</para></listitem>
 385       </varlistentry>
 386
 387       <varlistentry>
 388         <term><option>--uuid=</option></term>
 389
 390         <listitem><para>Set the specified UUID for the container. The
 391         init system will initialize
 392         <filename>/etc/machine-id</filename> from this if this file is
 393         not set yet. Note that this option takes effect only if
 394         <filename>/etc/machine-id</filename> in the container is
 395         unpopulated.</para></listitem>
 396       </varlistentry>
 397
 398       <varlistentry>
 399         <term><option>--slice=</option></term>
 400
 401         <listitem><para>Make the container part of the specified
 402         slice, instead of the default
 403         <filename>machine.slice</filename>. This is only applies if
 404         the machine is run in its own scope unit, i.e. if
 405         <option>--keep-unit</option> is not used.</para>
 406         </listitem>
 407       </varlistentry>
 408
 409       <varlistentry>
 410         <term><option>--property=</option></term>
 411
 412         <listitem><para>Set a unit property on the scope unit to
 413         register for the machine. This only applies if the machine is
 414         run in its own scope unit, i.e. if
 415         <option>--keep-unit</option> is not used. Takes unit property
 416         assignments in the same format as <command>systemctl
 417         set-property</command>. This is useful to set memory limits
 418         and similar for machines.</para>
 419         </listitem>
 420       </varlistentry>
 421
 422       <varlistentry>
 423         <term><option>--private-users=</option></term>
 424
 425         <listitem><para>Controls user namespacing. If enabled, the container will run with its own private set of UNIX
 426         user and group ids (UIDs and GIDs). This involves mapping the private UIDs/GIDs used in the container (starting
 427         with the container's root user 0 and up) to a range of UIDs/GIDs on the host that are not used for other
 428         purposes (usually in the range beyond the host's UID/GID 65536). The parameter may be specified as follows:</para>
 429
 430         <orderedlist>
 431           <listitem><para>If one or two colon-separated numbers are specified, user namespacing is turned on. The first
 432           parameter specifies the first host UID/GID to assign to the container, the second parameter specifies the
 433           number of host UIDs/GIDs to assign to the container. If the second parameter is omitted, 65536 UIDs/GIDs are
 434           assigned.</para></listitem>
 435
 436           <listitem><para>If the parameter is omitted, or true, user namespacing is turned on. The UID/GID range to
 437           use is determined automatically from the file ownership of the root directory of the container's directory
 438           tree. To use this option, make sure to prepare the directory tree in advance, and ensure that all files and
 439           directories in it are owned by UIDs/GIDs in the range you'd like to use. Also, make sure that used file ACLs
 440           exclusively reference UIDs/GIDs in the appropriate range. If this mode is used the number of UIDs/GIDs
 441           assigned to the container for use is 65536, and the UID/GID of the root directory must be a multiple of
 442           65536.</para></listitem>
 443
 444           <listitem><para>If the parameter is false, user namespacing is turned off. This is the default.</para>
 445           </listitem>
 446
 447           <listitem><para>The special value <literal>pick</literal> turns on user namespacing. In this case the UID/GID
 448           range is automatically chosen. As first step, the file owner of the root directory of the container's
 449           directory tree is read, and it is checked that it is currently not used by the system otherwise (in
 450           particular, that no other container is using it). If this check is successful, the UID/GID range determined
 451           this way is used, similar to the behavior if "yes" is specified. If the check is not successful (and thus
 452           the UID/GID range indicated in the root directory's file owner is already used elsewhere) a new – currently
 453           unused – UID/GID range of 65536 UIDs/GIDs is randomly chosen between the host UID/GIDs of 524288 and
 454           1878982656, always starting at a multiple of 65536. This setting implies
 455           <option>--private-users-chown</option> (see below), which has the effect that the files and directories in
 456           the container's directory tree will be owned by the appropriate users of the range picked. Using this option
 457           makes user namespace behavior fully automatic. Note that the first invocation of a previously unused
 458           container image might result in picking a new UID/GID range for it, and thus in the (possibly expensive) file
 459           ownership adjustment operation. However, subsequent invocations of the container will be cheap (unless of
 460           course the picked UID/GID range is assigned to a different use by then).</para></listitem>
 461         </orderedlist>
 462
 463         <para>It is recommended to assign at least 65536 UIDs/GIDs to each container, so that the usable UID/GID range in the
 464         container covers 16 bit. For best security, do not assign overlapping UID/GID ranges to multiple containers. It is
 465         hence a good idea to use the upper 16 bit of the host 32-bit UIDs/GIDs as container identifier, while the lower 16
 466         bit encode the container UID/GID used. This is in fact the behavior enforced by the
 467         <option>--private-users=pick</option> option.</para>
 468
 469         <para>When user namespaces are used, the GID range assigned to each container is always chosen identical to the
 470         UID range.</para>
 471
 472         <para>In most cases, using <option>--private-users=pick</option> is the recommended option as it enhances
 473         container security massively and operates fully automatically in most cases.</para>
 474
 475         <para>Note that the picked UID/GID range is not written to <filename>/etc/passwd</filename> or
 476         <filename>/etc/group</filename>. In fact, the allocation of the range is not stored persistently anywhere,
 477         except in the file ownership of the files and directories of the container.</para>
 478
 479         <para>Note that when user namespacing is used file ownership on disk reflects this, and all of the container's
 480         files and directories are owned by the container's effective user and group IDs. This means that copying files
 481         from and to the container image requires correction of the numeric UID/GID values, according to the UID/GID
 482         shift applied.</para></listitem>
 483       </varlistentry>
 484
 485       <varlistentry>
 486         <term><option>--private-users-chown</option></term>
 487
 488         <listitem><para>If specified, all files and directories in the container's directory tree will adjusted so that
 489         they are owned to the appropriate UIDs/GIDs selected for the container (see above). This operation is
 490         potentially expensive, as it involves descending and iterating through the full directory tree of the
 491         container. Besides actual file ownership, file ACLs are adjusted as well.</para>
 492
 493         <para>This option is implied if <option>--private-users=pick</option> is used. This option has no effect if
 494         user namespacing is not used.</para></listitem>
 495       </varlistentry>
 496
 497       <varlistentry>
 498         <term><option>-U</option></term>
 499
 500         <listitem><para>If the kernel supports the user namespaces feature, equivalent to
 501         <option>--private-users=pick --private-users-chown</option>, otherwise equivalent to
 502         <option>--private-users=no</option>.</para>
 503
 504         <para>Note that <option>-U</option> is the default if the
 505         <filename>systemd-nspawn@.service</filename> template unit file is used.</para>
 506
 507         <para>Note: it is possible to undo the effect of <option>--private-users-chown</option> (or
 508         <option>-U</option>) on the file system by redoing the operation with the first UID of 0:</para>
 509
 510         <programlisting>systemd-nspawn … --private-users=0 --private-users-chown</programlisting>
 511         </listitem>
 512       </varlistentry>
 513
 514       <varlistentry>
 515         <term><option>--private-network</option></term>
 516
 517         <listitem><para>Disconnect networking of the container from
 518         the host. This makes all network interfaces unavailable in the
 519         container, with the exception of the loopback device and those
 520         specified with <option>--network-interface=</option> and
 521         configured with <option>--network-veth</option>. If this
 522         option is specified, the CAP_NET_ADMIN capability will be
 523         added to the set of capabilities the container retains. The
 524         latter may be disabled by using
 525         <option>--drop-capability=</option>.</para></listitem>
 526       </varlistentry>
 527
 528       <varlistentry>
 529         <term><option>--network-interface=</option></term>
 530
 531         <listitem><para>Assign the specified network interface to the
 532         container. This will remove the specified interface from the
 533         calling namespace and place it in the container. When the
 534         container terminates, it is moved back to the host namespace.
 535         Note that <option>--network-interface=</option> implies
 536         <option>--private-network</option>. This option may be used
 537         more than once to add multiple network interfaces to the
 538         container.</para></listitem>
 539       </varlistentry>
 540
 541       <varlistentry>
 542         <term><option>--network-macvlan=</option></term>
 543
 544         <listitem><para>Create a <literal>macvlan</literal> interface
 545         of the specified Ethernet network interface and add it to the
 546         container. A <literal>macvlan</literal> interface is a virtual
 547         interface that adds a second MAC address to an existing
 548         physical Ethernet link. The interface in the container will be
 549         named after the interface on the host, prefixed with
 550         <literal>mv-</literal>. Note that
 551         <option>--network-macvlan=</option> implies
 552         <option>--private-network</option>. This option may be used
 553         more than once to add multiple network interfaces to the
 554         container.</para></listitem>
 555       </varlistentry>
 556
 557       <varlistentry>
 558         <term><option>--network-ipvlan=</option></term>
 559
 560         <listitem><para>Create an <literal>ipvlan</literal> interface
 561         of the specified Ethernet network interface and add it to the
 562         container. An <literal>ipvlan</literal> interface is a virtual
 563         interface, similar to a <literal>macvlan</literal> interface,
 564         which uses the same MAC address as the underlying interface.
 565         The interface in the container will be named after the
 566         interface on the host, prefixed with <literal>iv-</literal>.
 567         Note that <option>--network-ipvlan=</option> implies
 568         <option>--private-network</option>. This option may be used
 569         more than once to add multiple network interfaces to the
 570         container.</para></listitem>
 571       </varlistentry>
 572
 573       <varlistentry>
 574         <term><option>-n</option></term>
 575         <term><option>--network-veth</option></term>
 576
 577         <listitem><para>Create a virtual Ethernet link (<literal>veth</literal>) between host and container. The host
 578         side of the Ethernet link will be available as a network interface named after the container's name (as
 579         specified with <option>--machine=</option>), prefixed with <literal>ve-</literal>. The container side of the
 580         Ethernet link will be named <literal>host0</literal>. The <option>--network-veth</option> option implies
 581         <option>--private-network</option>.</para>
 582
 583         <para>Note that
 584         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 585         includes by default a network file <filename>/usr/lib/systemd/network/80-container-ve.network</filename>
 586         matching the host-side interfaces created this way, which contains settings to enable automatic address
 587         provisioning on the created virtual link via DHCP, as well as automatic IP routing onto the host's external
 588         network interfaces. It also contains <filename>/usr/lib/systemd/network/80-container-host0.network</filename>
 589         matching the container-side interface created this way, containing settings to enable client side address
 590         assignment via DHCP. In case <filename>systemd-networkd</filename> is running on both the host and inside the
 591         container, automatic IP communication from the container to the host is thus available, with further
 592         connectivity to the external network.</para>
 593
 594         <para>Note that <option>--network-veth</option> is the default if the
 595         <filename>systemd-nspawn@.service</filename> template unit file is used.</para>
 596         </listitem>
 597       </varlistentry>
 598
 599       <varlistentry>
 600         <term><option>--network-veth-extra=</option></term>
 601
 602         <listitem><para>Adds an additional virtual Ethernet link
 603         between host and container. Takes a colon-separated pair of
 604         host interface name and container interface name. The latter
 605         may be omitted in which case the container and host sides will
 606         be assigned the same name. This switch is independent of
 607         <option>--network-veth</option>, and — in contrast — may be
 608         used multiple times, and allows configuration of the network
 609         interface names. Note that <option>--network-bridge=</option>
 610         has no effect on interfaces created with
 611         <option>--network-veth-extra=</option>.</para></listitem>
 612       </varlistentry>
 613
 614       <varlistentry>
 615         <term><option>--network-bridge=</option></term>
 616
 617         <listitem><para>Adds the host side of the Ethernet link created with <option>--network-veth</option> to the
 618         specified Ethernet bridge interface. Expects a valid network interface name of a bridge device as
 619         argument. Note that <option>--network-bridge=</option> implies <option>--network-veth</option>. If this option
 620         is used, the host side of the Ethernet link will use the <literal>vb-</literal> prefix instead of
 621         <literal>ve-</literal>.</para></listitem>
 622       </varlistentry>
 623
 624       <varlistentry>
 625         <term><option>--network-zone=</option></term>
 626
 627         <listitem><para>Creates a virtual Ethernet link (<literal>veth</literal>) to the container and adds it to an
 628         automatically managed Ethernet bridge interface. The bridge interface is named after the passed argument,
 629         prefixed with <literal>vz-</literal>. The bridge interface is automatically created when the first container
 630         configured for its name is started, and is automatically removed when the last container configured for its
 631         name exits. Hence, each bridge interface configured this way exists only as long as there's at least one
 632         container referencing it running. This option is very similar to <option>--network-bridge=</option>, besides
 633         this automatic creation/removal of the bridge device.</para>
 634
 635         <para>This setting makes it easy to place multiple related containers on a common, virtual Ethernet-based
 636         broadcast domain, here called a "zone". Each container may only be part of one zone, but each zone may contain
 637         any number of containers. Each zone is referenced by its name. Names may be chosen freely (as long as they form
 638         valid network interface names when prefixed with <literal>vz-</literal>), and it is sufficient to pass the same
 639         name to the <option>--network-zones=</option> switch of the various concurrently running containers to join
 640         them in one zone.</para>
 641
 642         <para>Note that
 643         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 644         includes by default a network file <filename>/usr/lib/systemd/network/80-container-vz.network</filename>
 645         matching the bridge interfaces created this way, which contains settings to enable automatic address
 646         provisioning on the created virtual network via DHCP, as well as automatic IP routing onto the host's external
 647         network interfaces. Using <option>--network-zone=</option> is hence in most cases fully automatic and
 648         sufficient to connect multiple local containers in a joined broadcast domain to the host, with further
 649         connectivity to the external network.</para>
 650         </listitem>
 651       </varlistentry>
 652
 653       <varlistentry>
 654         <term><option>-p</option></term>
 655         <term><option>--port=</option></term>
 656
 657         <listitem><para>If private networking is enabled, maps an IP
 658         port on the host onto an IP port on the container. Takes a
 659         protocol specifier (either <literal>tcp</literal> or
 660         <literal>udp</literal>), separated by a colon from a host port
 661         number in the range 1 to 65535, separated by a colon from a
 662         container port number in the range from 1 to 65535. The
 663         protocol specifier and its separating colon may be omitted, in
 664         which case <literal>tcp</literal> is assumed. The container
 665         port number and its colon may be omitted, in which case the
 666         same port as the host port is implied. This option is only
 667         supported if private networking is used, such as with
 668         <option>--network-veth</option>, <option>--network-zone=</option>
 669         <option>--network-bridge=</option>.</para></listitem>
 670       </varlistentry>
 671
 672       <varlistentry>
 673         <term><option>-Z</option></term>
 674         <term><option>--selinux-context=</option></term>
 675
 676         <listitem><para>Sets the SELinux security context to be used
 677         to label processes in the container.</para>
 678         </listitem>
 679       </varlistentry>
 680
 681       <varlistentry>
 682         <term><option>-L</option></term>
 683         <term><option>--selinux-apifs-context=</option></term>
 684
 685         <listitem><para>Sets the SELinux security context to be used
 686         to label files in the virtual API file systems in the
 687         container.</para>
 688         </listitem>
 689       </varlistentry>
 690
 691       <varlistentry>
 692         <term><option>--capability=</option></term>
 693
 694         <listitem><para>List one or more additional capabilities to
 695         grant the container. Takes a comma-separated list of
 696         capability names, see
 697         <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 698         for more information. Note that the following capabilities
 699         will be granted in any way: CAP_CHOWN, CAP_DAC_OVERRIDE,
 700         CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 701         CAP_KILL, CAP_LEASE, CAP_LINUX_IMMUTABLE,
 702         CAP_NET_BIND_SERVICE, CAP_NET_BROADCAST, CAP_NET_RAW,
 703         CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP, CAP_SETUID,
 704         CAP_SYS_ADMIN, CAP_SYS_CHROOT, CAP_SYS_NICE, CAP_SYS_PTRACE,
 705         CAP_SYS_TTY_CONFIG, CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 706         CAP_AUDIT_WRITE, CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN is
 707         retained if <option>--private-network</option> is specified.
 708         If the special value <literal>all</literal> is passed, all
 709         capabilities are retained.</para></listitem>
 710       </varlistentry>
 711
 712       <varlistentry>
 713         <term><option>--drop-capability=</option></term>
 714
 715         <listitem><para>Specify one or more additional capabilities to
 716         drop for the container. This allows running the container with
 717         fewer capabilities than the default (see
 718         above).</para></listitem>
 719       </varlistentry>
 720
 721       <varlistentry>
 722         <term><option>--kill-signal=</option></term>
 723
 724         <listitem><para>Specify the process signal to send to the
 725         container's PID 1 when nspawn itself receives SIGTERM, in
 726         order to trigger an orderly shutdown of the
 727         container. Defaults to SIGRTMIN+3 if <option>--boot</option>
 728         is used (on systemd-compatible init systems SIGRTMIN+3
 729         triggers an orderly shutdown). For a list of valid signals, see
 730         <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
 731       </varlistentry>
 732
 733       <varlistentry>
 734         <term><option>--link-journal=</option></term>
 735
 736         <listitem><para>Control whether the container's journal shall
 737         be made visible to the host system. If enabled, allows viewing
 738         the container's journal files from the host (but not vice
 739         versa). Takes one of <literal>no</literal>,
 740         <literal>host</literal>, <literal>try-host</literal>,
 741         <literal>guest</literal>, <literal>try-guest</literal>,
 742         <literal>auto</literal>. If <literal>no</literal>, the journal
 743         is not linked. If <literal>host</literal>, the journal files
 744         are stored on the host file system (beneath
 745         <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 746         and the subdirectory is bind-mounted into the container at the
 747         same location. If <literal>guest</literal>, the journal files
 748         are stored on the guest file system (beneath
 749         <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 750         and the subdirectory is symlinked into the host at the same
 751         location. <literal>try-host</literal> and
 752         <literal>try-guest</literal> do the same but do not fail if
 753         the host does not have persistent journaling enabled. If
 754         <literal>auto</literal> (the default), and the right
 755         subdirectory of <filename>/var/log/journal</filename> exists,
 756         it will be bind mounted into the container. If the
 757         subdirectory does not exist, no linking is performed.
 758         Effectively, booting a container once with
 759         <literal>guest</literal> or <literal>host</literal> will link
 760         the journal persistently if further on the default of
 761         <literal>auto</literal> is used.</para>
 762
 763         <para>Note that <option>--link-journal=try-guest</option> is the default if the
 764         <filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem>
 765       </varlistentry>
 766
 767       <varlistentry>
 768         <term><option>-j</option></term>
 769
 770         <listitem><para>Equivalent to
 771         <option>--link-journal=try-guest</option>.</para></listitem>
 772       </varlistentry>
 773
 774       <varlistentry>
 775         <term><option>--read-only</option></term>
 776
 777         <listitem><para>Mount the root file system read-only for the
 778         container.</para></listitem>
 779       </varlistentry>
 780
 781       <varlistentry>
 782         <term><option>--bind=</option></term>
 783         <term><option>--bind-ro=</option></term>
 784
 785         <listitem><para>Bind mount a file or directory from the host into the container. Takes one of: a path
 786         argument — in which case the specified path will be mounted from the host to the same path in the container, or
 787         a colon-separated pair of paths — in which case the first specified path is the source in the host, and the
 788         second path is the destination in the container, or a colon-separated triple of source path, destination path
 789         and mount options. The source path may optionally be prefixed with a <literal>+</literal> character. If so, the
 790         source path is taken relative to the image's root directory. This permits setting up bind mounts within the
 791         container image. The source path may be specified as empty string, in which case a temporary directory below
 792         the host's <filename>/var/tmp</filename> directory is used. It is automatically removed when the container is
 793         shut down. Mount options are comma-separated and currently, only <option>rbind</option> and
 794         <option>norbind</option> are allowed, controlling whether to create a recursive or a regular bind
 795         mount. Defaults to "rbind". Backslash escapes are interpreted, so <literal>\:</literal> may be used to embed
 796         colons in either path.  This option may be specified multiple times for creating multiple independent bind
 797         mount points. The <option>--bind-ro=</option> option creates read-only bind mounts.</para></listitem>
 798       </varlistentry>
 799
 800       <varlistentry>
 801         <term><option>--tmpfs=</option></term>
 802
 803         <listitem><para>Mount a tmpfs file system into the container.
 804         Takes a single absolute path argument that specifies where to
 805         mount the tmpfs instance to (in which case the directory
 806         access mode will be chosen as 0755, owned by root/root), or
 807         optionally a colon-separated pair of path and mount option
 808         string that is used for mounting (in which case the kernel
 809         default for access mode and owner will be chosen, unless
 810         otherwise specified). This option is particularly useful for
 811         mounting directories such as <filename>/var</filename> as
 812         tmpfs, to allow state-less systems, in particular when
 813         combined with <option>--read-only</option>.
 814         Backslash escapes are interpreted in the path, so
 815         <literal>\:</literal> may be used to embed colons in the path.
 816         </para></listitem>
 817       </varlistentry>
 818
 819       <varlistentry>
 820         <term><option>--overlay=</option></term>
 821         <term><option>--overlay-ro=</option></term>
 822
 823         <listitem><para>Combine multiple directory trees into one
 824         overlay file system and mount it into the container. Takes a
 825         list of colon-separated paths to the directory trees to
 826         combine and the destination mount point.</para>
 827
 828         <para>Backslash escapes are interpreted in the paths, so
 829         <literal>\:</literal> may be used to embed colons in the paths.
 830         </para>
 831
 832         <para>If three or more paths are specified, then the last
 833         specified path is the destination mount point in the
 834         container, all paths specified before refer to directory trees
 835         on the host and are combined in the specified order into one
 836         overlay file system. The left-most path is hence the lowest
 837         directory tree, the second-to-last path the highest directory
 838         tree in the stacking order. If <option>--overlay-ro=</option>
 839         is used instead of <option>--overlay=</option>, a read-only
 840         overlay file system is created. If a writable overlay file
 841         system is created, all changes made to it are written to the
 842         highest directory tree in the stacking order, i.e. the
 843         second-to-last specified.</para>
 844
 845         <para>If only two paths are specified, then the second
 846         specified path is used both as the top-level directory tree in
 847         the stacking order as seen from the host, as well as the mount
 848         point for the overlay file system in the container. At least
 849         two paths have to be specified.</para>
 850
 851         <para>The source paths may optionally be prefixed with <literal>+</literal> character. If so they are taken
 852         relative to the image's root directory. The uppermost source path may also be specified as empty string, in
 853         which case a temporary directory below the host's <filename>/var/tmp</filename> is used. The directory is
 854         removed automatically when the container is shut down. This behaviour is useful in order to make read-only
 855         container directories writable while the container is running. For example, use the
 856         <literal>--overlay=+/var::/var</literal> option in order to automatically overlay a writable temporary
 857         directory on a read-only <filename>/var</filename> directory.</para>
 858
 859         <para>For details about overlay file systems, see <ulink
 860         url="https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt">overlayfs.txt</ulink>. Note
 861         that the semantics of overlay file systems are substantially
 862         different from normal file systems, in particular regarding
 863         reported device and inode information. Device and inode
 864         information may change for a file while it is being written
 865         to, and processes might see out-of-date versions of files at
 866         times. Note that this switch automatically derives the
 867         <literal>workdir=</literal> mount option for the overlay file
 868         system from the top-level directory tree, making it a sibling
 869         of it. It is hence essential that the top-level directory tree
 870         is not a mount point itself (since the working directory must
 871         be on the same file system as the top-most directory
 872         tree). Also note that the <literal>lowerdir=</literal> mount
 873         option receives the paths to stack in the opposite order of
 874         this switch.</para></listitem>
 875       </varlistentry>
 876
 877       <varlistentry>
 878         <term><option>-E <replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term>
 879         <term><option>--setenv=<replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term>
 880
 881         <listitem><para>Specifies an environment variable assignment
 882         to pass to the init process in the container, in the format
 883         <literal>NAME=VALUE</literal>. This may be used to override
 884         the default variables or to set additional variables. This
 885         parameter may be used more than once.</para></listitem>
 886       </varlistentry>
 887
 888       <varlistentry>
 889         <term><option>--register=</option></term>
 890
 891         <listitem><para>Controls whether the container is registered
 892         with
 893         <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 894         Takes a boolean argument, which defaults to <literal>yes</literal>.
 895         This option should be enabled when the container runs a full
 896         Operating System (more specifically: an init system), and is
 897         useful to ensure that the container is accessible via
 898         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 899         and shown by tools such as
 900         <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 901         If the container does not run an init system, it is
 902         recommended to set this option to <literal>no</literal>.</para></listitem>
 903       </varlistentry>
 904
 905       <varlistentry>
 906         <term><option>--keep-unit</option></term>
 907
 908         <listitem><para>Instead of creating a transient scope unit to
 909         run the container in, simply register the service or scope
 910         unit <command>systemd-nspawn</command> has been invoked in
 911         with
 912         <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 913         This has no effect if <option>--register=no</option> is used.
 914         This switch should be used if
 915         <command>systemd-nspawn</command> is invoked from within a
 916         service unit, and the service unit's sole purpose is to run a
 917         single <command>systemd-nspawn</command> container. This
 918         option is not available if run from a user
 919         session.</para></listitem>
 920       </varlistentry>
 921
 922       <varlistentry>
 923         <term><option>--personality=</option></term>
 924
 925         <listitem><para>Control the architecture ("personality")
 926         reported by
 927         <citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 928         in the container. Currently, only <literal>x86</literal> and
 929         <literal>x86-64</literal> are supported. This is useful when
 930         running a 32-bit container on a 64-bit host. If this setting
 931         is not used, the personality reported in the container is the
 932         same as the one reported on the host.</para></listitem>
 933       </varlistentry>
 934
 935       <varlistentry>
 936         <term><option>-q</option></term>
 937         <term><option>--quiet</option></term>
 938
 939         <listitem><para>Turns off any status output by the tool
 940         itself. When this switch is used, the only output from nspawn
 941         will be the console output of the container OS
 942         itself.</para></listitem>
 943       </varlistentry>
 944
 945       <varlistentry>
 946         <term><option>--volatile</option></term>
 947         <term><option>--volatile=</option><replaceable>MODE</replaceable></term>
 948
 949         <listitem><para>Boots the container in volatile mode. When no
 950         mode parameter is passed or when mode is specified as
 951         <option>yes</option>, full volatile mode is enabled. This
 952         means the root directory is mounted as a mostly unpopulated
 953         <literal>tmpfs</literal> instance, and
 954         <filename>/usr</filename> from the OS tree is mounted into it
 955         in read-only mode (the system thus starts up with read-only OS
 956         image, but pristine state and configuration, any changes
 957         are lost on shutdown). When the mode parameter
 958         is specified as <option>state</option>, the OS tree is
 959         mounted read-only, but <filename>/var</filename> is mounted as
 960         a <literal>tmpfs</literal> instance into it (the system thus
 961         starts up with read-only OS resources and configuration, but
 962         pristine state, and any changes to the latter are lost on
 963         shutdown). When the mode parameter is specified as
 964         <option>no</option> (the default), the whole OS tree is made
 965         available writable.</para>
 966
 967         <para>This option provides similar functionality for containers as the <literal>systemd.volatile=</literal>
 968         kernel command line switch provides for host systems. See
 969         <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
 970         details.</para>
 971
 972         <para>Note that enabling this setting will only work correctly with operating systems in the container that can
 973         boot up with only <filename>/usr</filename> mounted, and are able to automatically populate
 974         <filename>/var</filename>, and also <filename>/etc</filename> in case of
 975         <literal>--volatile=yes</literal>.</para></listitem>
 976       </varlistentry>
 977
 978       <varlistentry>
 979         <term><option>--settings=</option><replaceable>MODE</replaceable></term>
 980
 981         <listitem><para>Controls whether
 982         <command>systemd-nspawn</command> shall search for and use
 983         additional per-container settings from
 984         <filename>.nspawn</filename> files. Takes a boolean or the
 985         special values <option>override</option> or
 986         <option>trusted</option>.</para>
 987
 988         <para>If enabled (the default), a settings file named after the
 989         machine (as specified with the <option>--machine=</option>
 990         setting, or derived from the directory or image file name)
 991         with the suffix <filename>.nspawn</filename> is searched in
 992         <filename>/etc/systemd/nspawn/</filename> and
 993         <filename>/run/systemd/nspawn/</filename>. If it is found
 994         there, its settings are read and used. If it is not found
 995         there, it is subsequently searched in the same directory as the
 996         image file or in the immediate parent of the root directory of
 997         the container. In this case, if the file is found, its settings
 998         will be also read and used, but potentially unsafe settings
 999         are ignored. Note that in both these cases, settings on the
1000         command line take precedence over the corresponding settings
1001         from loaded <filename>.nspawn</filename> files, if both are
1002         specified. Unsafe settings are considered all settings that
1003         elevate the container's privileges or grant access to
1004         additional resources such as files or directories of the
1005         host. For details about the format and contents of
1006         <filename>.nspawn</filename> files, consult
1007         <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1008
1009         <para>If this option is set to <option>override</option>, the
1010         file is searched, read and used the same way, however, the order of
1011         precedence is reversed: settings read from the
1012         <filename>.nspawn</filename> file will take precedence over
1013         the corresponding command line options, if both are
1014         specified.</para>
1015
1016         <para>If this option is set to <option>trusted</option>, the
1017         file is searched, read and used the same way, but regardless
1018         of being found in <filename>/etc/systemd/nspawn/</filename>,
1019         <filename>/run/systemd/nspawn/</filename> or next to the image
1020         file or container root directory, all settings will take
1021         effect, however, command line arguments still take precedence
1022         over corresponding settings.</para>
1023
1024         <para>If disabled, no <filename>.nspawn</filename> file is read
1025         and no settings except the ones on the command line are in
1026         effect.</para></listitem>
1027       </varlistentry>
1028
1029       <varlistentry>
1030         <term><option>--notify-ready=</option></term>
1031
1032         <listitem><para>Configures support for notifications from the container's init process.
1033         <option>--notify-ready=</option> takes a boolean (<option>no</option> and  <option>yes</option>).
1034         With option <option>no</option> systemd-nspawn notifies systemd
1035         with a <literal>READY=1</literal> message when the init process is created.
1036         With option <option>yes</option> systemd-nspawn waits for the
1037         <literal>READY=1</literal> message from the init process in the container
1038         before sending its own to systemd. For more details about notifications
1039         see <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).</para></listitem>
1040       </varlistentry>
1041
1042       <xi:include href="standard-options.xml" xpointer="help" />
1043       <xi:include href="standard-options.xml" xpointer="version" />
1044     </variablelist>
1045
1046   </refsect1>
1047
1048   <refsect1>
1049     <title>Examples</title>
1050
1051     <example>
1052       <title>Download a Fedora image and start a shell in it</title>
1053
1054       <programlisting># machinectl pull-raw --verify=no \
1055       https://download.fedoraproject.org/pub/fedora/linux/releases/25/CloudImages/x86_64/images/Fedora-Cloud-Base-25-1.3.x86_64.raw.xz
1056 # systemd-nspawn -M Fedora-Cloud-Base-25-1.3.x86_64.raw</programlisting>
1057
1058       <para>This downloads an image using
1059       <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1060       and opens a shell in it.</para>
1061     </example>
1062
1063     <example>
1064       <title>Build and boot a minimal Fedora distribution in a container</title>
1065
1066       <programlisting># dnf -y --releasever=25 --installroot=/srv/mycontainer \
1067       --disablerepo='*' --enablerepo=fedora --enablerepo=updates install \
1068       systemd passwd dnf fedora-release vim-minimal
1069 # systemd-nspawn -bD /srv/mycontainer</programlisting>
1070
1071       <para>This installs a minimal Fedora distribution into the
1072       directory <filename noindex='true'>/srv/mycontainer/</filename>
1073       and then boots an OS in a namespace container in it.</para>
1074     </example>
1075
1076     <example>
1077       <title>Spawn a shell in a container of a minimal Debian unstable distribution</title>
1078
1079       <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
1080 # systemd-nspawn -D ~/debian-tree/</programlisting>
1081
1082       <para>This installs a minimal Debian unstable distribution into
1083       the directory <filename>~/debian-tree/</filename> and then
1084       spawns a shell in a namespace container in it.</para>
1085     </example>
1086
1087     <example>
1088       <title>Boot a minimal Arch Linux distribution in a container</title>
1089
1090       <programlisting># pacstrap -c -d ~/arch-tree/ base
1091 # systemd-nspawn -bD ~/arch-tree/</programlisting>
1092
1093       <para>This installs a minimal Arch Linux distribution into the
1094       directory <filename>~/arch-tree/</filename> and then boots an OS
1095       in a namespace container in it.</para>
1096     </example>
1097
1098     <example>
1099       <title>Boot into an ephemeral snapshot of the host system</title>
1100
1101       <programlisting># systemd-nspawn -D / -xb</programlisting>
1102
1103       <para>This runs a copy of the host system in a snapshot which is removed immediately when the container
1104       exits. All file system changes made during runtime will be lost on shutdown, hence.</para>
1105     </example>
1106
1107     <example>
1108       <title>Run a container with SELinux sandbox security contexts</title>
1109
1110       <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
1111 # systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 \
1112       -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh</programlisting>
1113     </example>
1114
1115     <example>
1116       <title>Run a container with an OSTree deployment</title>
1117
1118       <programlisting># systemd-nspawn -b -i ~/image.raw \
1119       --pivot-root=/ostree/deploy/$OS/deploy/$CHECKSUM:/sysroot \
1120       --bind=+/sysroot/ostree/deploy/$OS/var:/var</programlisting>
1121     </example>
1122   </refsect1>
1123
1124   <refsect1>
1125     <title>Exit status</title>
1126
1127     <para>The exit code of the program executed in the container is
1128     returned.</para>
1129   </refsect1>
1130
1131   <refsect1>
1132     <title>See Also</title>
1133     <para>
1134       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1135       <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1136       <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1137       <citerefentry project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1138       <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1139       <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1140       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1141       <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1142       <citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1143     </para>
1144   </refsect1>
1145
1146 </refentry>