1SYSTEMD-NSPAWN(1) systemd-nspawn SYSTEMD-NSPAWN(1)
2
6 systemd-nspawn - Spawn a command or OS in a light-weight container
7
9 systemd-nspawn [OPTIONS...] [COMMAND [ARGS...]]
10 systemd-nspawn --boot [OPTIONS...] [ARGS...]
12
14 systemd-nspawn may be used to run a command or OS in a light-weight
15 namespace container. In many ways it is similar to chroot(1), but more
16 powerful since it fully virtualizes the file system hierarchy, as well
17 as the process tree, the various IPC subsystems and the host and domain
18 name.
19 systemd-nspawn may be invoked on any directory tree containing an
21 operating system tree, using the --directory= command line option. By
22 using the --machine= option an OS tree is automatically searched for in
23 a couple of locations, most importantly in /var/lib/machines/, the
24 suggested directory to place OS container images installed on the
25 system.
26 In contrast to chroot(1) systemd-nspawn may be used to boot full
28 Linux-based operating systems in a container.
29 systemd-nspawn limits access to various kernel interfaces in the
31 container to read-only, such as /sys/, /proc/sys/ or /sys/fs/selinux/.
32 The host's network interfaces and the system clock may not be changed
33 from within the container. Device nodes may not be created. The host
34 system cannot be rebooted and kernel modules may not be loaded from
35 within the container.
36 Use a tool like dnf(8), debootstrap(8), or pacman(8) to set up an OS
38 directory tree suitable as file system hierarchy for systemd-nspawn
39 containers. See the Examples section below for details on suitable
40 invocation of these commands.
41 As a safety check systemd-nspawn will verify the existence of
43 /usr/lib/os-release or /etc/os-release in the container tree before
44 starting the container (see os-release(5)). It might be necessary to
45 add this file to the container tree manually if the OS of the container
46 is too old to contain this file out-of-the-box.
47 systemd-nspawn may be invoked directly from the interactive command
49 line or run as system service in the background. In this mode each
50 container instance runs as its own service instance; a default template
51 unit file systemd-nspawn@.service is provided to make this easy, taking
52 the container name as instance identifier. Note that different default
53 options apply when systemd-nspawn is invoked by the template unit file
54 than interactively on the command line. Most importantly the template
55 unit file makes use of the --boot which is not the default in case
56 systemd-nspawn is invoked from the interactive command line. Further
57 differences with the defaults are documented along with the various
58 supported options below.
59 The machinectl(1) tool may be used to execute a number of operations on
61 containers. In particular it provides easy-to-use commands to run
62 containers as system services using the systemd-nspawn@.service
63 template unit file.
64 Along with each container a settings file with the .nspawn suffix may
66 exist, containing additional settings to apply when running the
67 container. See systemd.nspawn(5) for details. Settings files override
68 the default options used by the systemd-nspawn@.service template unit
69 file, making it usually unnecessary to alter this template file
70 directly.
71 Note that systemd-nspawn will mount file systems private to the
73 container to /dev/, /run/ and similar. These will not be visible
74 outside of the container, and their contents will be lost when the
75 container exits.
76 Note that running two systemd-nspawn containers from the same directory
78 tree will not make processes in them see each other. The PID namespace
79 separation of the two containers is complete and the containers will
80 share very few runtime objects except for the underlying file system.
81 Use machinectl(1)'s login or shell commands to request an additional
82 login session in a running container.
83 systemd-nspawn implements the Container Interface[1] specification.
85 While running, containers invoked with systemd-nspawn are registered
87 with the systemd-machined(8) service that keeps track of running
88 containers, and provides programming interfaces to interact with them.
89
91 If option -b is specified, the arguments are used as arguments for the
92 init program. Otherwise, COMMAND specifies the program to launch in the
93 container, and the remaining arguments are used as arguments for this
94 program. If --boot is not used and no arguments are specified, a shell
95 is launched in the container.
96 The following options are understood:
98 -q, --quiet
100 Turns off any status output by the tool itself. When this switch is
101 used, the only output from nspawn will be the console output of the
102 container OS itself.
103 --settings=MODE
105 Controls whether systemd-nspawn shall search for and use additional
106 per-container settings from .nspawn files. Takes a boolean or the
107 special values override or trusted.
108 If enabled (the default), a settings file named after the machine
110 (as specified with the --machine= setting, or derived from the
111 directory or image file name) with the suffix .nspawn is searched
112 in /etc/systemd/nspawn/ and /run/systemd/nspawn/. If it is found
113 there, its settings are read and used. If it is not found there, it
114 is subsequently searched in the same directory as the image file or
115 in the immediate parent of the root directory of the container. In
116 this case, if the file is found, its settings will be also read and
117 used, but potentially unsafe settings are ignored. Note that in
118 both these cases, settings on the command line take precedence over
119 the corresponding settings from loaded .nspawn files, if both are
120 specified. Unsafe settings are considered all settings that elevate
121 the container's privileges or grant access to additional resources
122 such as files or directories of the host. For details about the
123 format and contents of .nspawn files, consult systemd.nspawn(5).
124 If this option is set to override, the file is searched, read and
126 used the same way, however, the order of precedence is reversed:
127 settings read from the .nspawn file will take precedence over the
128 corresponding command line options, if both are specified.
129 If this option is set to trusted, the file is searched, read and
131 used the same way, but regardless of being found in
132 /etc/systemd/nspawn/, /run/systemd/nspawn/ or next to the image
133 file or container root directory, all settings will take effect,
134 however, command line arguments still take precedence over
135 corresponding settings.
136 If disabled, no .nspawn file is read and no settings except the
138 ones on the command line are in effect.
139 Image Options
141 -D, --directory=
142 Directory to use as file system root for the container.
143 If neither --directory=, nor --image= is specified the directory is
145 determined by searching for a directory named the same as the
146 machine name specified with --machine=. See machinectl(1) section
147 "Files and Directories" for the precise search path.
148 If neither --directory=, --image=, nor --machine= are specified,
150 the current directory will be used. May not be specified together
151 with --image=.
152 --template=
154 Directory or "btrfs" subvolume to use as template for the
155 container's root directory. If this is specified and the
156 container's root directory (as configured by --directory=) does not
157 yet exist it is created as "btrfs" snapshot (if supported) or plain
158 directory (otherwise) and populated from this template tree.
159 Ideally, the specified template path refers to the root of a
160 "btrfs" subvolume, in which case a simple copy-on-write snapshot is
161 taken, and populating the root directory is instant. If the
162 specified template path does not refer to the root of a "btrfs"
163 subvolume (or not even to a "btrfs" file system at all), the tree
164 is copied (though possibly in a 'reflink' copy-on-write scheme — if
165 the file system supports that), which can be substantially more
166 time-consuming. Note that the snapshot taken is of the specified
167 directory or subvolume, including all subdirectories and subvolumes
168 below it, but excluding any sub-mounts. May not be specified
169 together with --image= or --ephemeral.
170 Note that this switch leaves hostname, machine ID and all other
172 settings that could identify the instance unmodified.
173 -x, --ephemeral
175 If specified, the container is run with a temporary snapshot of its
176 file system that is removed immediately when the container
177 terminates. May not be specified together with --template=.
178 Note that this switch leaves hostname, machine ID and all other
180 settings that could identify the instance unmodified. Please note
181 that — as with --template= — taking the temporary snapshot is more
182 efficient on file systems that support subvolume snapshots or
183 'reflinks' natively ("btrfs" or new "xfs") than on more traditional
184 file systems that do not ("ext4"). Note that the snapshot taken is
185 of the specified directory or subvolume, including all
186 subdirectories and subvolumes below it, but excluding any
187 sub-mounts.
188 With this option no modifications of the container image are
190 retained. Use --volatile= (described below) for other mechanisms to
191 restrict persistency of container images during runtime.
192 -i, --image=
194 Disk image to mount the root directory for the container from.
195 Takes a path to a regular file or to a block device node. The file
196 or block device must contain either:
197 • An MBR partition table with a single partition of type 0x83
199 that is marked bootable.
200 • A GUID partition table (GPT) with a single partition of type
202 0fc63daf-8483-4772-8e79-3d69d8477de4.
203 • A GUID partition table (GPT) with a marked root partition which
205 is mounted as the root directory of the container. Optionally,
206 GPT images may contain a home and/or a server data partition
207 which are mounted to the appropriate places in the container.
208 All these partitions must be identified by the partition types
209 defined by the Discoverable Partitions Specification[2].
210 • No partition table, and a single file system spanning the whole
212 image.
213 On GPT images, if an EFI System Partition (ESP) is discovered, it
215 is automatically mounted to /efi (or /boot as fallback) in case a
216 directory by this name exists and is empty.
217 Partitions encrypted with LUKS are automatically decrypted. Also,
219 on GPT images dm-verity data integrity hash partitions are set up
220 if the root hash for them is specified using the --root-hash=
221 option.
222 Single file system images (i.e. file systems without a surrounding
224 partition table) can be opened using dm-verity if the integrity
225 data is passed using the --root-hash= and --verity-data= (and
226 optionally --root-hash-sig=) options.
227 Any other partitions, such as foreign partitions or swap partitions
229 are not mounted. May not be specified together with --directory=,
230 --template=.
231 --oci-bundle=
233 Takes the path to an OCI runtime bundle to invoke, as specified in
234 the OCI Runtime Specification[3]. In this case no .nspawn file is
235 loaded, and the root directory and various settings are read from
236 the OCI runtime JSON data (but data passed on the command line
237 takes precedence).
238 --read-only
240 Mount the container's root file system (and any other file systems
241 container in the container image) read-only. This has no effect on
242 additional mounts made with --bind=, --tmpfs= and similar options.
243 This mode is implied if the container image file or directory is
244 marked read-only itself. It is also implied if --volatile= is used.
245 In this case the container image on disk is strictly read-only,
246 while changes are permitted but kept non-persistently in memory
247 only. For further details, see below.
248 --volatile, --volatile=MODE
250 Boots the container in volatile mode. When no mode parameter is
251 passed or when mode is specified as yes, full volatile mode is
252 enabled. This means the root directory is mounted as a mostly
253 unpopulated "tmpfs" instance, and /usr/ from the OS tree is mounted
254 into it in read-only mode (the system thus starts up with read-only
255 OS image, but pristine state and configuration, any changes are
256 lost on shutdown). When the mode parameter is specified as state,
257 the OS tree is mounted read-only, but /var/ is mounted as a
258 writable "tmpfs" instance into it (the system thus starts up with
259 read-only OS resources and configuration, but pristine state, and
260 any changes to the latter are lost on shutdown). When the mode
261 parameter is specified as overlay the read-only root file system is
262 combined with a writable tmpfs instance through "overlayfs", so
263 that it appears at it normally would, but any changes are applied
264 to the temporary file system only and lost when the container is
265 terminated. When the mode parameter is specified as no (the
266 default), the whole OS tree is made available writable (unless
267 --read-only is specified, see above).
268 Note that if one of the volatile modes is chosen, its effect is
270 limited to the root file system (or /var/ in case of state), and
271 any other mounts placed in the hierarchy are unaffected —
272 regardless if they are established automatically (e.g. the EFI
273 system partition that might be mounted to /efi/ or /boot/) or
274 explicitly (e.g. through an additional command line option such as
275 --bind=, see below). This means, even if --volatile=overlay is used
276 changes to /efi/ or /boot/ are prohibited in case such a partition
277 exists in the container image operated on, and even if
278 --volatile=state is used the hypothetical file /etc/foobar is
279 potentially writable if --bind=/etc/foobar if used to mount it from
280 outside the read-only container /etc/ directory.
281 The --ephemeral option is closely related to this setting, and
283 provides similar behaviour by making a temporary, ephemeral copy of
284 the whole OS image and executing that. For further details, see
285 above.
286 The --tmpfs= and --overlay= options provide similar functionality,
288 but for specific sub-directories of the OS image only. For details,
289 see below.
290 This option provides similar functionality for containers as the
292 "systemd.volatile=" kernel command line switch provides for host
293 systems. See kernel-command-line(7) for details.
294 Note that setting this option to yes or state will only work
296 correctly with operating systems in the container that can boot up
297 with only /usr/ mounted, and are able to automatically populate
298 /var/ (and /etc/ in case of "--volatile=yes"). Specifically, this
299 means that operating systems that follow the historic split of
300 /bin/ and /lib/ (and related directories) from /usr/ (i.e. where
301 the former are not symlinks into the latter) are not supported by
302 "--volatile=yes" as container payload. The overlay option does not
303 require any particular preparations in the OS, but do note that
304 "overlayfs" behaviour differs from regular file systems in a number
305 of ways, and hence compatibility is limited.
306 --root-hash=
308 Takes a data integrity (dm-verity) root hash specified in
309 hexadecimal. This option enables data integrity checks using
310 dm-verity, if the used image contains the appropriate integrity
311 data (see above). The specified hash must match the root hash of
312 integrity data, and is usually at least 256 bits (and hence 64
313 formatted hexadecimal characters) long (in case of SHA256 for
314 example). If this option is not specified, but the image file
315 carries the "user.verity.roothash" extended file attribute (see
316 xattr(7)), then the root hash is read from it, also as formatted
317 hexadecimal characters. If the extended file attribute is not found
318 (or is not supported by the underlying file system), but a file
319 with the .roothash suffix is found next to the image file, bearing
320 otherwise the same name (except if the image has the .raw suffix,
321 in which case the root hash file must not have it in its name), the
322 root hash is read from it and automatically used, also as formatted
323 hexadecimal characters.
324 Note that this configures the root hash for the root file system.
326 Disk images may also contain separate file systems for the /usr/
327 hierarchy, which may be Verity protected as well. The root hash for
328 this protection may be configured via the "user.verity.usrhash"
329 extended file attribute or via a .usrhash file adjacent to the disk
330 image, following the same format and logic as for the root hash for
331 the root file system described here. Note that there's currently no
332 switch to configure the root hash for the /usr/ from the command
333 line.
334 Also see the RootHash= option in systemd.exec(5).
336 --root-hash-sig=
338 Takes a PKCS7 signature of the --root-hash= option. The semantics
339 are the same as for the RootHashSignature= option, see
340 systemd.exec(5).
341 --verity-data=
343 Takes the path to a data integrity (dm-verity) file. This option
344 enables data integrity checks using dm-verity, if a root-hash is
345 passed and if the used image itself does not contains the integrity
346 data. The integrity data must be matched by the root hash. If this
347 option is not specified, but a file with the .verity suffix is
348 found next to the image file, bearing otherwise the same name
349 (except if the image has the .raw suffix, in which case the verity
350 data file must not have it in its name), the verity data is read
351 from it and automatically used.
352 --pivot-root=
354 Pivot the specified directory to / inside the container, and either
355 unmount the container's old root, or pivot it to another specified
356 directory. Takes one of: a path argument — in which case the
357 specified path will be pivoted to / and the old root will be
358 unmounted; or a colon-separated pair of new root path and pivot
359 destination for the old root. The new root path will be pivoted to
360 /, and the old / will be pivoted to the other directory. Both paths
361 must be absolute, and are resolved in the container's file system
362 namespace.
363 This is for containers which have several bootable directories in
365 them; for example, several OSTree[4] deployments. It emulates the
366 behavior of the boot loader and initial RAM disk which normally
367 select which directory to mount as the root and start the
368 container's PID 1 in.
369 Execution Options
371 -a, --as-pid2
372 Invoke the shell or specified program as process ID (PID) 2 instead
373 of PID 1 (init). By default, if neither this option nor --boot is
374 used, the selected program is run as the process with PID 1, a mode
375 only suitable for programs that are aware of the special semantics
376 that the process with PID 1 has on UNIX. For example, it needs to
377 reap all processes reparented to it, and should implement sysvinit
378 compatible signal handling (specifically: it needs to reboot on
379 SIGINT, reexecute on SIGTERM, reload configuration on SIGHUP, and
380 so on). With --as-pid2 a minimal stub init process is run as PID 1
381 and the selected program is executed as PID 2 (and hence does not
382 need to implement any special semantics). The stub init process
383 will reap processes as necessary and react appropriately to
384 signals. It is recommended to use this mode to invoke arbitrary
385 commands in containers, unless they have been modified to run
386 correctly as PID 1. Or in other words: this switch should be used
387 for pretty much all commands, except when the command refers to an
388 init or shell implementation, as these are generally capable of
389 running correctly as PID 1. This option may not be combined with
390 --boot.
391 -b, --boot
393 Automatically search for an init program and invoke it as PID 1,
394 instead of a shell or a user supplied program. If this option is
395 used, arguments specified on the command line are used as arguments
396 for the init program. This option may not be combined with
397 --as-pid2.
398 The following table explains the different modes of invocation and
400 relationship to --as-pid2 (see above):
401 Table 1. Invocation Mode
403 ┌──────────────────────┬────────────────────────────┐
404 │Switch │ Explanation │
405 ├──────────────────────┼────────────────────────────┤
406 │Neither --as-pid2 nor │ The passed parameters are │
407 │--boot specified │ interpreted as the command │
408 │ │ line, which is executed as │
409 │ │ PID 1 in the container. │
410 ├──────────────────────┼────────────────────────────┤
411 │--as-pid2 specified │ The passed parameters are │
412 │ │ interpreted as the command │
413 │ │ line, which is executed as │
414 │ │ PID 2 in the container. A │
415 │ │ stub init process is run │
416 │ │ as PID 1. │
417 ├──────────────────────┼────────────────────────────┤
418 │--boot specified │ An init program is │
419 │ │ automatically searched for │
420 │ │ and run as PID 1 in the │
421 │ │ container. The passed │
422 │ │ parameters are used as │
423 │ │ invocation parameters for │
424 │ │ this process. │
425 └──────────────────────┴────────────────────────────┘
426 Note that --boot is the default mode of operation if the
427 systemd-nspawn@.service template unit file is used.
428 --chdir=
430 Change to the specified working directory before invoking the
431 process in the container. Expects an absolute path in the
432 container's file system namespace.
433 -E NAME=VALUE, --setenv=NAME=VALUE
435 Specifies an environment variable assignment to pass to the init
436 process in the container, in the format "NAME=VALUE". This may be
437 used to override the default variables or to set additional
438 variables. This parameter may be used more than once.
439 -u, --user=
441 After transitioning into the container, change to the specified
442 user defined in the container's user database. Like all other
443 systemd-nspawn features, this is not a security feature and
444 provides protection against accidental destructive operations only.
445 --kill-signal=
447 Specify the process signal to send to the container's PID 1 when
448 nspawn itself receives SIGTERM, in order to trigger an orderly
449 shutdown of the container. Defaults to SIGRTMIN+3 if --boot is used
450 (on systemd-compatible init systems SIGRTMIN+3 triggers an orderly
451 shutdown). If --boot is not used and this option is not specified
452 the container's processes are terminated abruptly via SIGKILL. For
453 a list of valid signals, see signal(7).
454 --notify-ready=
456 Configures support for notifications from the container's init
457 process. --notify-ready= takes a boolean (no and yes). With option
458 no systemd-nspawn notifies systemd with a "READY=1" message when
459 the init process is created. With option yes systemd-nspawn waits
460 for the "READY=1" message from the init process in the container
461 before sending its own to systemd. For more details about
462 notifications see sd_notify(3).
463 System Identity Options
465 -M, --machine=
466 Sets the machine name for this container. This name may be used to
467 identify this container during its runtime (for example in tools
468 like machinectl(1) and similar), and is used to initialize the
469 container's hostname (which the container can choose to override,
470 however). If not specified, the last component of the root
471 directory path of the container is used, possibly suffixed with a
472 random identifier in case --ephemeral mode is selected. If the root
473 directory selected is the host's root directory the host's hostname
474 is used as default instead.
475 --hostname=
477 Controls the hostname to set within the container, if different
478 from the machine name. Expects a valid hostname as argument. If
479 this option is used, the kernel hostname of the container will be
480 set to this value, otherwise it will be initialized to the machine
481 name as controlled by the --machine= option described above. The
482 machine name is used for various aspect of identification of the
483 container from the outside, the kernel hostname configurable with
484 this option is useful for the container to identify itself from the
485 inside. It is usually a good idea to keep both forms of
486 identification synchronized, in order to avoid confusion. It is
487 hence recommended to avoid usage of this option, and use --machine=
488 exclusively. Note that regardless whether the container's hostname
489 is initialized from the name set with --hostname= or the one set
490 with --machine=, the container can later override its kernel
491 hostname freely on its own as well.
492 --uuid=
494 Set the specified UUID for the container. The init system will
495 initialize /etc/machine-id from this if this file is not set yet.
496 Note that this option takes effect only if /etc/machine-id in the
497 container is unpopulated.
498 Property Options
500 -S, --slice=
501 Make the container part of the specified slice, instead of the
502 default machine.slice. This applies only if the machine is run in
503 its own scope unit, i.e. if --keep-unit isn't used.
504 --property=
506 Set a unit property on the scope unit to register for the machine.
507 This applies only if the machine is run in its own scope unit, i.e.
508 if --keep-unit isn't used. Takes unit property assignments in the
509 same format as systemctl set-property. This is useful to set memory
510 limits and similar for container.
511 --register=
513 Controls whether the container is registered with systemd-
514 machined(8). Takes a boolean argument, which defaults to "yes".
515 This option should be enabled when the container runs a full
516 Operating System (more specifically: a system and service manager
517 as PID 1), and is useful to ensure that the container is accessible
518 via machinectl(1) and shown by tools such as ps(1). If the
519 container does not run a service manager, it is recommended to set
520 this option to "no".
521 --keep-unit
523 Instead of creating a transient scope unit to run the container in,
524 simply use the service or scope unit systemd-nspawn has been
525 invoked in. If --register=yes is set this unit is registered with
526 systemd-machined(8). This switch should be used if systemd-nspawn
527 is invoked from within a service unit, and the service unit's sole
528 purpose is to run a single systemd-nspawn container. This option is
529 not available if run from a user session.
530 Note that passing --keep-unit disables the effect of --slice= and
532 --property=. Use --keep-unit and --register=no in combination to
533 disable any kind of unit allocation or registration with
534 systemd-machined.
535 User Namespacing Options
537 --private-users=
538 Controls user namespacing. If enabled, the container will run with
539 its own private set of UNIX user and group ids (UIDs and GIDs).
540 This involves mapping the private UIDs/GIDs used in the container
541 (starting with the container's root user 0 and up) to a range of
542 UIDs/GIDs on the host that are not used for other purposes (usually
543 in the range beyond the host's UID/GID 65536). The parameter may be
544 specified as follows:
545 1. If one or two colon-separated numbers are specified, user
547 namespacing is turned on. The first parameter specifies the
548 first host UID/GID to assign to the container, the second
549 parameter specifies the number of host UIDs/GIDs to assign to
550 the container. If the second parameter is omitted, 65536
551 UIDs/GIDs are assigned.
552 2. If the parameter is omitted, or true, user namespacing is
554 turned on. The UID/GID range to use is determined automatically
555 from the file ownership of the root directory of the
556 container's directory tree. To use this option, make sure to
557 prepare the directory tree in advance, and ensure that all
558 files and directories in it are owned by UIDs/GIDs in the range
559 you'd like to use. Also, make sure that used file ACLs
560 exclusively reference UIDs/GIDs in the appropriate range. If
561 this mode is used the number of UIDs/GIDs assigned to the
562 container for use is 65536, and the UID/GID of the root
563 directory must be a multiple of 65536.
564 3. If the parameter is false, user namespacing is turned off. This
566 is the default.
567 4. The special value "pick" turns on user namespacing. In this
569 case the UID/GID range is automatically chosen. As first step,
570 the file owner of the root directory of the container's
571 directory tree is read, and it is checked that it is currently
572 not used by the system otherwise (in particular, that no other
573 container is using it). If this check is successful, the
574 UID/GID range determined this way is used, similar to the
575 behavior if "yes" is specified. If the check is not successful
576 (and thus the UID/GID range indicated in the root directory's
577 file owner is already used elsewhere) a new – currently unused
578 – UID/GID range of 65536 UIDs/GIDs is randomly chosen between
579 the host UID/GIDs of 524288 and 1878982656, always starting at
580 a multiple of 65536, and, if possible, consistently hashed from
581 the machine name. This setting implies --private-users-chown
582 (see below), which has the effect that the files and
583 directories in the container's directory tree will be owned by
584 the appropriate users of the range picked. Using this option
585 makes user namespace behavior fully automatic. Note that the
586 first invocation of a previously unused container image might
587 result in picking a new UID/GID range for it, and thus in the
588 (possibly expensive) file ownership adjustment operation.
589 However, subsequent invocations of the container will be cheap
590 (unless of course the picked UID/GID range is assigned to a
591 different use by then).
592 It is recommended to assign at least 65536 UIDs/GIDs to each
594 container, so that the usable UID/GID range in the container covers
595 16 bit. For best security, do not assign overlapping UID/GID ranges
596 to multiple containers. It is hence a good idea to use the upper 16
597 bit of the host 32-bit UIDs/GIDs as container identifier, while the
598 lower 16 bit encode the container UID/GID used. This is in fact the
599 behavior enforced by the --private-users=pick option.
600 When user namespaces are used, the GID range assigned to each
602 container is always chosen identical to the UID range.
603 In most cases, using --private-users=pick is the recommended option
605 as it enhances container security massively and operates fully
606 automatically in most cases.
607 Note that the picked UID/GID range is not written to /etc/passwd or
609 /etc/group. In fact, the allocation of the range is not stored
610 persistently anywhere, except in the file ownership of the files
611 and directories of the container.
612 Note that when user namespacing is used file ownership on disk
614 reflects this, and all of the container's files and directories are
615 owned by the container's effective user and group IDs. This means
616 that copying files from and to the container image requires
617 correction of the numeric UID/GID values, according to the UID/GID
618 shift applied.
619 --private-users-chown
621 If specified, all files and directories in the container's
622 directory tree will be adjusted so that they are owned by the
623 appropriate UIDs/GIDs selected for the container (see above). This
624 operation is potentially expensive, as it involves iterating
625 through the full directory tree of the container. Besides actual
626 file ownership, file ACLs are adjusted as well.
627 This option is implied if --private-users=pick is used. This option
629 has no effect if user namespacing is not used.
630 -U
632 If the kernel supports the user namespaces feature, equivalent to
633 --private-users=pick --private-users-chown, otherwise equivalent to
634 --private-users=no.
635 Note that -U is the default if the systemd-nspawn@.service template
637 unit file is used.
638 Note: it is possible to undo the effect of --private-users-chown
640 (or -U) on the file system by redoing the operation with the first
641 UID of 0:
642 systemd-nspawn ... --private-users=0 --private-users-chown
644 Networking Options
646 --private-network
647 Disconnect networking of the container from the host. This makes
648 all network interfaces unavailable in the container, with the
649 exception of the loopback device and those specified with
650 --network-interface= and configured with --network-veth. If this
651 option is specified, the CAP_NET_ADMIN capability will be added to
652 the set of capabilities the container retains. The latter may be
653 disabled by using --drop-capability=. If this option is not
654 specified (or implied by one of the options listed below), the
655 container will have full access to the host network.
656 --network-interface=
658 Assign the specified network interface to the container. This will
659 remove the specified interface from the calling namespace and place
660 it in the container. When the container terminates, it is moved
661 back to the calling namespace. Note that --network-interface=
662 implies --private-network. This option may be used more than once
663 to add multiple network interfaces to the container.
664 Note that any network interface specified this way must already
666 exist at the time the container is started. If the container shall
667 be started automatically at boot via a systemd-nspawn@.service unit
668 file instance, it might hence make sense to add a unit file drop-in
669 to the service instance (e.g.
670 /etc/systemd/system/systemd-nspawn@foobar.service.d/50-network.conf)
671 with contents like the following:
672 [Unit]
674 Wants=sys-subsystem-net-devices-ens1.device
675 After=sys-subsystem-net-devices-ens1.device
676 This will make sure that activation of the container service will
678 be delayed until the "ens1" network interface has shown up. This is
679 required since hardware probing is fully asynchronous, and network
680 interfaces might be discovered only later during the boot process,
681 after the container would normally be started without these
682 explicit dependencies.
683 --network-macvlan=
685 Create a "macvlan" interface of the specified Ethernet network
686 interface and add it to the container. A "macvlan" interface is a
687 virtual interface that adds a second MAC address to an existing
688 physical Ethernet link. The interface in the container will be
689 named after the interface on the host, prefixed with "mv-". Note
690 that --network-macvlan= implies --private-network. This option may
691 be used more than once to add multiple network interfaces to the
692 container.
693 As with --network-interface=, the underlying Ethernet network
695 interface must already exist at the time the container is started,
696 and thus similar unit file drop-ins as described above might be
697 useful.
698 --network-ipvlan=
700 Create an "ipvlan" interface of the specified Ethernet network
701 interface and add it to the container. An "ipvlan" interface is a
702 virtual interface, similar to a "macvlan" interface, which uses the
703 same MAC address as the underlying interface. The interface in the
704 container will be named after the interface on the host, prefixed
705 with "iv-". Note that --network-ipvlan= implies --private-network.
706 This option may be used more than once to add multiple network
707 interfaces to the container.
708 As with --network-interface=, the underlying Ethernet network
710 interface must already exist at the time the container is started,
711 and thus similar unit file drop-ins as described above might be
712 useful.
713 -n, --network-veth
715 Create a virtual Ethernet link ("veth") between host and container.
716 The host side of the Ethernet link will be available as a network
717 interface named after the container's name (as specified with
718 --machine=), prefixed with "ve-". The container side of the
719 Ethernet link will be named "host0". The --network-veth option
720 implies --private-network.
721 Note that systemd-networkd.service(8) includes by default a network
723 file /usr/lib/systemd/network/80-container-ve.network matching the
724 host-side interfaces created this way, which contains settings to
725 enable automatic address provisioning on the created virtual link
726 via DHCP, as well as automatic IP routing onto the host's external
727 network interfaces. It also contains
728 /usr/lib/systemd/network/80-container-host0.network matching the
729 container-side interface created this way, containing settings to
730 enable client side address assignment via DHCP. In case
731 systemd-networkd is running on both the host and inside the
732 container, automatic IP communication from the container to the
733 host is thus available, with further connectivity to the external
734 network.
735 Note that --network-veth is the default if the
737 systemd-nspawn@.service template unit file is used.
738 Note that on Linux network interface names may have a length of 15
740 characters at maximum, while container names may have a length up
741 to 64 characters. As this option derives the host-side interface
742 name from the container name the name is possibly truncated. Thus,
743 care needs to be taken to ensure that interface names remain unique
744 in this case, or even better container names are generally not
745 chosen longer than 12 characters, to avoid the truncation. If the
746 name is truncated, systemd-nspawn will automatically append a
747 4-digit hash value to the name to reduce the chance of collisions.
748 However, the hash algorithm is not collision-free. (See
749 systemd.net-naming-scheme(7) for details on older naming algorithms
750 for this interface). Alternatively, the --network-veth-extra=
751 option may be used, which allows free configuration of the
752 host-side interface name independently of the container name — but
753 might require a bit more additional configuration in case bridging
754 in a fashion similar to --network-bridge= is desired.
755 --network-veth-extra=
757 Adds an additional virtual Ethernet link between host and
758 container. Takes a colon-separated pair of host interface name and
759 container interface name. The latter may be omitted in which case
760 the container and host sides will be assigned the same name. This
761 switch is independent of --network-veth, and — in contrast — may be
762 used multiple times, and allows configuration of the network
763 interface names. Note that --network-bridge= has no effect on
764 interfaces created with --network-veth-extra=.
765 --network-bridge=
767 Adds the host side of the Ethernet link created with --network-veth
768 to the specified Ethernet bridge interface. Expects a valid network
769 interface name of a bridge device as argument. Note that
770 --network-bridge= implies --network-veth. If this option is used,
771 the host side of the Ethernet link will use the "vb-" prefix
772 instead of "ve-". Regardless of the used naming prefix the same
773 network interface name length limits imposed by Linux apply, along
774 with the complications this creates (for details see above).
775 As with --network-interface=, the underlying bridge network
777 interface must already exist at the time the container is started,
778 and thus similar unit file drop-ins as described above might be
779 useful.
780 --network-zone=
782 Creates a virtual Ethernet link ("veth") to the container and adds
783 it to an automatically managed Ethernet bridge interface. The
784 bridge interface is named after the passed argument, prefixed with
785 "vz-". The bridge interface is automatically created when the first
786 container configured for its name is started, and is automatically
787 removed when the last container configured for its name exits.
788 Hence, each bridge interface configured this way exists only as
789 long as there's at least one container referencing it running. This
790 option is very similar to --network-bridge=, besides this automatic
791 creation/removal of the bridge device.
792 This setting makes it easy to place multiple related containers on
794 a common, virtual Ethernet-based broadcast domain, here called a
795 "zone". Each container may only be part of one zone, but each zone
796 may contain any number of containers. Each zone is referenced by
797 its name. Names may be chosen freely (as long as they form valid
798 network interface names when prefixed with "vz-"), and it is
799 sufficient to pass the same name to the --network-zone= switch of
800 the various concurrently running containers to join them in one
801 zone.
802 Note that systemd-networkd.service(8) includes by default a network
804 file /usr/lib/systemd/network/80-container-vz.network matching the
805 bridge interfaces created this way, which contains settings to
806 enable automatic address provisioning on the created virtual
807 network via DHCP, as well as automatic IP routing onto the host's
808 external network interfaces. Using --network-zone= is hence in most
809 cases fully automatic and sufficient to connect multiple local
810 containers in a joined broadcast domain to the host, with further
811 connectivity to the external network.
812 --network-namespace-path=
814 Takes the path to a file representing a kernel network namespace
815 that the container shall run in. The specified path should refer to
816 a (possibly bind-mounted) network namespace file, as exposed by the
817 kernel below /proc/$PID/ns/net. This makes the container enter the
818 given network namespace. One of the typical use cases is to give a
819 network namespace under /run/netns created by ip-netns(8), for
820 example, --network-namespace-path=/run/netns/foo. Note that this
821 option cannot be used together with other network-related options,
822 such as --private-network or --network-interface=.
823 -p, --port=
825 If private networking is enabled, maps an IP port on the host onto
826 an IP port on the container. Takes a protocol specifier (either
827 "tcp" or "udp"), separated by a colon from a host port number in
828 the range 1 to 65535, separated by a colon from a container port
829 number in the range from 1 to 65535. The protocol specifier and its
830 separating colon may be omitted, in which case "tcp" is assumed.
831 The container port number and its colon may be omitted, in which
832 case the same port as the host port is implied. This option is only
833 supported if private networking is used, such as with
834 --network-veth, --network-zone= --network-bridge=.
835 Security Options
837 --capability=
838 List one or more additional capabilities to grant the container.
839 Takes a comma-separated list of capability names, see
840 capabilities(7) for more information. Note that the following
841 capabilities will be granted in any way: CAP_AUDIT_CONTROL,
842 CAP_AUDIT_WRITE, CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
843 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER, CAP_KILL, CAP_LEASE,
844 CAP_LINUX_IMMUTABLE, CAP_MKNOD, CAP_NET_BIND_SERVICE,
845 CAP_NET_BROADCAST, CAP_NET_RAW, CAP_SETFCAP, CAP_SETGID,
846 CAP_SETPCAP, CAP_SETUID, CAP_SYS_ADMIN, CAP_SYS_BOOT,
847 CAP_SYS_CHROOT, CAP_SYS_NICE, CAP_SYS_PTRACE, CAP_SYS_RESOURCE,
848 CAP_SYS_TTY_CONFIG. Also CAP_NET_ADMIN is retained if
849 --private-network is specified. If the special value "all" is
850 passed, all capabilities are retained.
851 If the special value of "help" is passed, the program will print
853 known capability names and exit.
854 This option sets the bounding set of capabilities which also limits
856 the ambient capabilities as given with the --ambient-capability=.
857 --drop-capability=
859 Specify one or more additional capabilities to drop for the
860 container. This allows running the container with fewer
861 capabilities than the default (see above).
862 If the special value of "help" is passed, the program will print
864 known capability names and exit.
865 This option sets the bounding set of capabilities which also limits
867 the ambient capabilities as given with the --ambient-capability=.
868 --ambient-capability=
870 Specify one or more additional capabilities to pass in the
871 inheritable and ambient set to the program started within the
872 container. The value "all" is not supported for this setting.
873 All capabilities specified here must be in the set allowed with the
875 --capability= and --drop-capability= options. Otherwise, an error
876 message will be shown.
877 This option cannot be combined with the boot mode of the container
879 (as requested via --boot).
880 If the special value of "help" is passed, the program will print
882 known capability names and exit.
883 --no-new-privileges=
885 Takes a boolean argument. Specifies the value of the
886 PR_SET_NO_NEW_PRIVS flag for the container payload. Defaults to
887 off. When turned on the payload code of the container cannot
888 acquire new privileges, i.e. the "setuid" file bit as well as file
889 system capabilities will not have an effect anymore. See prctl(2)
890 for details about this flag.
891 --system-call-filter=
893 Alter the system call filter applied to containers. Takes a
894 space-separated list of system call names or group names (the
895 latter prefixed with "@", as listed by the syscall-filter command
896 of systemd-analyze(1)). Passed system calls will be permitted. The
897 list may optionally be prefixed by "~", in which case all listed
898 system calls are prohibited. If this command line option is used
899 multiple times the configured lists are combined. If both a
900 positive and a negative list (that is one system call list without
901 and one with the "~" prefix) are configured, the negative list
902 takes precedence over the positive list. Note that systemd-nspawn
903 always implements a system call allow list (as opposed to a deny
904 list!), and this command line option hence adds or removes entries
905 from the default allow list, depending on the "~" prefix. Note that
906 the applied system call filter is also altered implicitly if
907 additional capabilities are passed using the --capabilities=.
908 -Z, --selinux-context=
910 Sets the SELinux security context to be used to label processes in
911 the container.
912 -L, --selinux-apifs-context=
914 Sets the SELinux security context to be used to label files in the
915 virtual API file systems in the container.
916 Resource Options
918 --rlimit=
919 Sets the specified POSIX resource limit for the container payload.
920 Expects an assignment of the form "LIMIT=SOFT:HARD" or
921 "LIMIT=VALUE", where LIMIT should refer to a resource limit type,
922 such as RLIMIT_NOFILE or RLIMIT_NICE. The SOFT and HARD fields
923 should refer to the numeric soft and hard resource limit values. If
924 the second form is used, VALUE may specify a value that is used
925 both as soft and hard limit. In place of a numeric value the
926 special string "infinity" may be used to turn off resource limiting
927 for the specific type of resource. This command line option may be
928 used multiple times to control limits on multiple limit types. If
929 used multiple times for the same limit type, the last use wins. For
930 details about resource limits see setrlimit(2). By default resource
931 limits for the container's init process (PID 1) are set to the same
932 values the Linux kernel originally passed to the host init system.
933 Note that some resource limits are enforced on resources counted
934 per user, in particular RLIMIT_NPROC. This means that unless user
935 namespacing is deployed (i.e. --private-users= is used, see
936 above), any limits set will be applied to the resource usage of the
937 same user on all local containers as well as the host. This means
938 particular care needs to be taken with these limits as they might
939 be triggered by possibly less trusted code. Example:
940 "--rlimit=RLIMIT_NOFILE=8192:16384".
941 --oom-score-adjust=
943 Changes the OOM ("Out Of Memory") score adjustment value for the
944 container payload. This controls /proc/self/oom_score_adj which
945 influences the preference with which this container is terminated
946 when memory becomes scarce. For details see proc(5). Takes an
947 integer in the range -1000...1000.
948 --cpu-affinity=
950 Controls the CPU affinity of the container payload. Takes a comma
951 separated list of CPU numbers or number ranges (the latter's start
952 and end value separated by dashes). See sched_setaffinity(2) for
953 details.
954 --personality=
956 Control the architecture ("personality") reported by uname(2) in
957 the container. Currently, only "x86" and "x86-64" are supported.
958 This is useful when running a 32-bit container on a 64-bit host. If
959 this setting is not used, the personality reported in the container
960 is the same as the one reported on the host.
961 Integration Options
963 --resolv-conf=
964 Configures how /etc/resolv.conf inside of the container shall be
965 handled (i.e. DNS configuration synchronization from host to
966 container). Takes one of "off", "copy-host", "copy-static",
967 "copy-uplink", "copy-stub", "replace-host", "replace-static",
968 "replace-uplink", "replace-stub", "bind-host", "bind-static",
969 "bind-uplink", "bind-stub", "delete" or "auto".
970 If set to "off" the /etc/resolv.conf file in the container is left
972 as it is included in the image, and neither modified nor bind
973 mounted over.
974 If set to "copy-host", the /etc/resolv.conf file from the host is
976 copied into the container, unless the file exists already and is
977 not a regular file (e.g. a symlink). Similar, if "replace-host" is
978 used the file is copied, replacing any existing inode, including
979 symlinks. Similar, if "bind-host" is used, the file is bind mounted
980 from the host into the container.
981 If set to "copy-static", "replace-static" or "bind-static" the
983 static resolv.conf file supplied with systemd-resolved.service(8)
984 (specifically: /usr/lib/systemd/resolv.conf) is copied or bind
985 mounted into the container.
986 If set to "copy-uplink", "replace-uplink" or "bind-uplink" the
988 uplink resolv.conf file managed by systemd-resolved.service
989 (specifically: /run/systemd/resolve/resolv.conf) is copied or bind
990 mounted into the container.
991 If set to "copy-stub", "replace-stub" or "bind-stub" the stub
993 resolv.conf file managed by systemd-resolved.service (specifically:
994 /run/systemd/resolve/stub-resolv.conf) is copied or bind mounted
995 into the container.
996 If set to "delete" the /etc/resolv.conf file in the container is
998 deleted if it exists.
999 Finally, if set to "auto" the file is left as it is if private
1001 networking is turned on (see --private-network). Otherwise, if
1002 systemd-resolved.service is running its stub resolv.conf file is
1003 used, and if not the host's /etc/resolv.conf file. In the latter
1004 cases the file is copied if the image is writable, and bind mounted
1005 otherwise.
1006 It's recommended to use "copy-..." or "replace-..." if the
1008 container shall be able to make changes to the DNS configuration on
1009 its own, deviating from the host's settings. Otherwise "bind" is
1010 preferable, as it means direct changes to /etc/resolv.conf in the
1011 container are not allowed, as it is a read-only bind mount (but
1012 note that if the container has enough privileges, it might simply
1013 go ahead and unmount the bind mount anyway). Note that both if the
1014 file is bind mounted and if it is copied no further propagation of
1015 configuration is generally done after the one-time early
1016 initialization (this is because the file is usually updated through
1017 copying and renaming). Defaults to "auto".
1018 --timezone=
1020 Configures how /etc/localtime inside of the container (i.e. local
1021 timezone synchronization from host to container) shall be handled.
1022 Takes one of "off", "copy", "bind", "symlink", "delete" or "auto".
1023 If set to "off" the /etc/localtime file in the container is left as
1024 it is included in the image, and neither modified nor bind mounted
1025 over. If set to "copy" the /etc/localtime file of the host is
1026 copied into the container. Similarly, if "bind" is used, the file
1027 is bind mounted from the host into the container. If set to
1028 "symlink", a symlink is created pointing from /etc/localtime in the
1029 container to the timezone file in the container that matches the
1030 timezone setting on the host. If set to "delete", the file in the
1031 container is deleted, should it exist. If set to "auto" and the
1032 /etc/localtime file of the host is a symlink, then "symlink" mode
1033 is used, and "copy" otherwise, except if the image is read-only in
1034 which case "bind" is used instead. Defaults to "auto".
1035 --link-journal=
1037 Control whether the container's journal shall be made visible to
1038 the host system. If enabled, allows viewing the container's journal
1039 files from the host (but not vice versa). Takes one of "no",
1040 "host", "try-host", "guest", "try-guest", "auto". If "no", the
1041 journal is not linked. If "host", the journal files are stored on
1042 the host file system (beneath /var/log/journal/machine-id) and the
1043 subdirectory is bind-mounted into the container at the same
1044 location. If "guest", the journal files are stored on the guest
1045 file system (beneath /var/log/journal/machine-id) and the
1046 subdirectory is symlinked into the host at the same location.
1047 "try-host" and "try-guest" do the same but do not fail if the host
1048 does not have persistent journaling enabled. If "auto" (the
1049 default), and the right subdirectory of /var/log/journal exists, it
1050 will be bind mounted into the container. If the subdirectory does
1051 not exist, no linking is performed. Effectively, booting a
1052 container once with "guest" or "host" will link the journal
1053 persistently if further on the default of "auto" is used.
1054 Note that --link-journal=try-guest is the default if the
1056 systemd-nspawn@.service template unit file is used.
1057 -j
1059 Equivalent to --link-journal=try-guest.
1060 Mount Options
1062 --bind=, --bind-ro=
1063 Bind mount a file or directory from the host into the container.
1064 Takes one of: a path argument — in which case the specified path
1065 will be mounted from the host to the same path in the container, or
1066 a colon-separated pair of paths — in which case the first specified
1067 path is the source in the host, and the second path is the
1068 destination in the container, or a colon-separated triple of source
1069 path, destination path and mount options. The source path may
1070 optionally be prefixed with a "+" character. If so, the source path
1071 is taken relative to the image's root directory. This permits
1072 setting up bind mounts within the container image. The source path
1073 may be specified as empty string, in which case a temporary
1074 directory below the host's /var/tmp/ directory is used. It is
1075 automatically removed when the container is shut down. Mount
1076 options are comma-separated and currently, only rbind and norbind
1077 are allowed, controlling whether to create a recursive or a regular
1078 bind mount. Defaults to "rbind". Backslash escapes are interpreted,
1079 so "\:" may be used to embed colons in either path. This option may
1080 be specified multiple times for creating multiple independent bind
1081 mount points. The --bind-ro= option creates read-only bind mounts.
1082 Note that when this option is used in combination with
1084 --private-users, the resulting mount points will be owned by the
1085 nobody user. That's because the mount and its files and directories
1086 continue to be owned by the relevant host users and groups, which
1087 do not exist in the container, and thus show up under the wildcard
1088 UID 65534 (nobody). If such bind mounts are created, it is
1089 recommended to make them read-only, using --bind-ro=.
1090 --inaccessible=
1092 Make the specified path inaccessible in the container. This
1093 over-mounts the specified path (which must exist in the container)
1094 with a file node of the same type that is empty and has the most
1095 restrictive access mode supported. This is an effective way to mask
1096 files, directories and other file system objects from the container
1097 payload. This option may be used more than once in case all
1098 specified paths are masked.
1099 --tmpfs=
1101 Mount a tmpfs file system into the container. Takes a single
1102 absolute path argument that specifies where to mount the tmpfs
1103 instance to (in which case the directory access mode will be chosen
1104 as 0755, owned by root/root), or optionally a colon-separated pair
1105 of path and mount option string that is used for mounting (in which
1106 case the kernel default for access mode and owner will be chosen,
1107 unless otherwise specified). Backslash escapes are interpreted in
1108 the path, so "\:" may be used to embed colons in the path.
1109 Note that this option cannot be used to replace the root file
1111 system of the container with a temporary file system. However, the
1112 --volatile= option described below provides similar functionality,
1113 with a focus on implementing stateless operating system images.
1114 --overlay=, --overlay-ro=
1116 Combine multiple directory trees into one overlay file system and
1117 mount it into the container. Takes a list of colon-separated paths
1118 to the directory trees to combine and the destination mount point.
1119 Backslash escapes are interpreted in the paths, so "\:" may be used
1121 to embed colons in the paths.
1122 If three or more paths are specified, then the last specified path
1124 is the destination mount point in the container, all paths
1125 specified before refer to directory trees on the host and are
1126 combined in the specified order into one overlay file system. The
1127 left-most path is hence the lowest directory tree, the
1128 second-to-last path the highest directory tree in the stacking
1129 order. If --overlay-ro= is used instead of --overlay=, a read-only
1130 overlay file system is created. If a writable overlay file system
1131 is created, all changes made to it are written to the highest
1132 directory tree in the stacking order, i.e. the second-to-last
1133 specified.
1134 If only two paths are specified, then the second specified path is
1136 used both as the top-level directory tree in the stacking order as
1137 seen from the host, as well as the mount point for the overlay file
1138 system in the container. At least two paths have to be specified.
1139 The source paths may optionally be prefixed with "+" character. If
1141 so they are taken relative to the image's root directory. The
1142 uppermost source path may also be specified as an empty string, in
1143 which case a temporary directory below the host's /var/tmp/ is
1144 used. The directory is removed automatically when the container is
1145 shut down. This behaviour is useful in order to make read-only
1146 container directories writable while the container is running. For
1147 example, use "--overlay=+/var::/var" in order to automatically
1148 overlay a writable temporary directory on a read-only /var/
1149 directory.
1150 For details about overlay file systems, see overlayfs.txt[5]. Note
1152 that the semantics of overlay file systems are substantially
1153 different from normal file systems, in particular regarding
1154 reported device and inode information. Device and inode information
1155 may change for a file while it is being written to, and processes
1156 might see out-of-date versions of files at times. Note that this
1157 switch automatically derives the "workdir=" mount option for the
1158 overlay file system from the top-level directory tree, making it a
1159 sibling of it. It is hence essential that the top-level directory
1160 tree is not a mount point itself (since the working directory must
1161 be on the same file system as the top-most directory tree). Also
1162 note that the "lowerdir=" mount option receives the paths to stack
1163 in the opposite order of this switch.
1164 Note that this option cannot be used to replace the root file
1166 system of the container with an overlay file system. However, the
1167 --volatile= option described above provides similar functionality,
1168 with a focus on implementing stateless operating system images.
1169 Input/Output Options
1171 --console=MODE
1172 Configures how to set up standard input, output and error output
1173 for the container payload, as well as the /dev/console device for
1174 the container. Takes one of interactive, read-only, passive, pipe
1175 or autopipe. If interactive, a pseudo-TTY is allocated and made
1176 available as /dev/console in the container. It is then
1177 bi-directionally connected to the standard input and output passed
1178 to systemd-nspawn. read-only is similar but only the output of the
1179 container is propagated and no input from the caller is read. If
1180 passive, a pseudo TTY is allocated, but it is not connected
1181 anywhere. In pipe mode no pseudo TTY is allocated, but the standard
1182 input, output and error output file descriptors passed to
1183 systemd-nspawn are passed on — as they are — to the container
1184 payload, see the following paragraph. Finally, autopipe mode
1185 operates like interactive when systemd-nspawn is invoked on a
1186 terminal, and like pipe otherwise. Defaults to interactive if
1187 systemd-nspawn is invoked from a terminal, and read-only otherwise.
1188 In pipe mode, /dev/console will not exist in the container. This
1190 means that the container payload generally cannot be a full init
1191 system as init systems tend to require /dev/console to be
1192 available. On the other hand, in this mode container invocations
1193 can be used within shell pipelines. This is because intermediary
1194 pseudo TTYs do not permit independent bidirectional propagation of
1195 the end-of-file (EOF) condition, which is necessary for shell
1196 pipelines to work correctly. Note that the pipe mode should be
1197 used carefully, as passing arbitrary file descriptors to less
1198 trusted container payloads might open up unwanted interfaces for
1199 access by the container payload. For example, if a passed file
1200 descriptor refers to a TTY of some form, APIs such as TIOCSTI may
1201 be used to synthesize input that might be used for escaping the
1202 container. Hence pipe mode should only be used if the payload is
1203 sufficiently trusted or when the standard input/output/error output
1204 file descriptors are known safe, for example pipes.
1205 --pipe, -P
1207 Equivalent to --console=pipe.
1208 Credentials
1210 --load-credential=ID:PATH, --set-credential=ID:VALUE
1211 Pass a credential to the container. These two options correspond to
1212 the LoadCredential= and SetCredential= settings in unit files. See
1213 systemd.exec(5) for details about these concepts, as well as the
1214 syntax of the option's arguments.
1215 Note: when systemd-nspawn runs as systemd system service it can
1217 propagate the credentials it received via
1218 LoadCredential=/SetCredential= to the container payload. A systemd
1219 service manager running as PID 1 in the container can further
1220 propagate them to the services it itself starts. It is thus
1221 possible to easily propagate credentials from a parent service
1222 manager to a container manager service and from there into its
1223 payload. This can even be done recursively.
1224 In order to embed binary data into the credential data for
1226 --set-credential= use C-style escaping (i.e. "\n" to embed a
1227 newline, or "\x00" to embed a NUL byte. Note that the invoking
1228 shell might already apply unescaping once, hence this might require
1229 double escaping!).
1230 Other
1232 --no-pager
1233 Do not pipe output into a pager.
1234 -h, --help
1236 Print a short help text and exit.
1237 --version
1239 Print a short version string and exit.
1240
1242 $SYSTEMD_LOG_LEVEL
1243 The maximum log level of emitted messages (messages with a higher
1244 log level, i.e. less important ones, will be suppressed). Either
1245 one of (in order of decreasing importance) emerg, alert, crit, err,
1246 warning, notice, info, debug, or an integer in the range 0...7. See
1247 syslog(3) for more information.
1248 $SYSTEMD_LOG_COLOR
1250 A boolean. If true, messages written to the tty will be colored
1251 according to priority.
1252 This setting is only useful when messages are written directly to
1254 the terminal, because journalctl(1) and other tools that display
1255 logs will color messages based on the log level on their own.
1256 $SYSTEMD_LOG_TIME
1258 A boolean. If true, log messages will be prefixed with a timestamp.
1259 This setting is only useful when messages are written directly to
1261 the terminal or a file, because journalctl(1) and other tools that
1262 display logs will attach timestamps based on the entry metadata on
1263 their own.
1264 $SYSTEMD_LOG_LOCATION
1266 A boolean. If true, messages will be prefixed with a filename and
1267 line number in the source code where the message originates.
1268 Note that the log location is often attached as metadata to journal
1270 entries anyway. Including it directly in the message text can
1271 nevertheless be convenient when debugging programs.
1272 $SYSTEMD_LOG_TID
1274 A boolean. If true, messages will be prefixed with the current
1275 numerical thread ID (TID).
1276 Note that the this information is attached as metadata to journal
1278 entries anyway. Including it directly in the message text can
1279 nevertheless be convenient when debugging programs.
1280 $SYSTEMD_LOG_TARGET
1282 The destination for log messages. One of console (log to the
1283 attached tty), console-prefixed (log to the attached tty but with
1284 prefixes encoding the log level and "facility", see syslog(3), kmsg
1285 (log to the kernel circular log buffer), journal (log to the
1286 journal), journal-or-kmsg (log to the journal if available, and to
1287 kmsg otherwise), auto (determine the appropriate log target
1288 automatically, the default), null (disable log output).
1289 $SYSTEMD_PAGER
1291 Pager to use when --no-pager is not given; overrides $PAGER. If
1292 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
1293 pager implementations are tried in turn, including less(1) and
1294 more(1), until one is found. If no pager implementation is
1295 discovered no pager is invoked. Setting this environment variable
1296 to an empty string or the value "cat" is equivalent to passing
1297 --no-pager.
1298 $SYSTEMD_LESS
1300 Override the options passed to less (by default "FRSXMK").
1301 Users might want to change two options in particular:
1303 K
1305 This option instructs the pager to exit immediately when Ctrl+C
1306 is pressed. To allow less to handle Ctrl+C itself to switch
1307 back to the pager command prompt, unset this option.
1308 If the value of $SYSTEMD_LESS does not include "K", and the
1310 pager that is invoked is less, Ctrl+C will be ignored by the
1311 executable, and needs to be handled by the pager.
1312 X
1314 This option instructs the pager to not send termcap
1315 initialization and deinitialization strings to the terminal. It
1316 is set by default to allow command output to remain visible in
1317 the terminal even after the pager exits. Nevertheless, this
1318 prevents some pager functionality from working, in particular
1319 paged output cannot be scrolled with the mouse.
1320 See less(1) for more discussion.
1322 $SYSTEMD_LESSCHARSET
1324 Override the charset passed to less (by default "utf-8", if the
1325 invoking terminal is determined to be UTF-8 compatible).
1326 $SYSTEMD_PAGERSECURE
1328 Takes a boolean argument. When true, the "secure" mode of the pager
1329 is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set
1330 at all, secure mode is enabled if the effective UID is not the same
1331 as the owner of the login session, see geteuid(2) and
1332 sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set
1333 when invoking the pager, and the pager shall disable commands that
1334 open or create new files or start new subprocesses. When
1335 $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known
1336 to implement secure mode will not be used. (Currently only less(1)
1337 implements secure mode.)
1338 Note: when commands are invoked with elevated privileges, for
1340 example under sudo(8) or pkexec(1), care must be taken to ensure
1341 that unintended interactive features are not enabled. "Secure" mode
1342 for the pager may be enabled automatically as describe above.
1343 Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited
1344 environment allows the user to invoke arbitrary commands. Note that
1345 if the $SYSTEMD_PAGER or $PAGER variables are to be honoured,
1346 $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
1347 completely disable the pager using --no-pager instead.
1348 $SYSTEMD_COLORS
1350 Takes a boolean argument. When true, systemd and related utilities
1351 will use colors in their output, otherwise the output will be
1352 monochrome. Additionally, the variable can take one of the
1353 following special values: "16", "256" to restrict the use of colors
1354 to the base 16 or 256 ANSI colors, respectively. This can be
1355 specified to override the automatic decision based on $TERM and
1356 what the console is connected to.
1357 $SYSTEMD_URLIFY
1359 The value must be a boolean. Controls whether clickable links
1360 should be generated in the output for terminal emulators supporting
1361 this. This can be specified to override the decision that systemd
1362 makes based on $TERM and other conditions.
1363
1365 Example 1. Download a Fedora image and start a shell in it
1366 # machinectl pull-raw --verify=no \
1368 https://download.fedoraproject.org/pub/fedora/linux/releases/33/Cloud/x86_64/images/Fedora-Cloud-Base-33-1.2.x86_64.raw.xz \
1369 Fedora-Cloud-Base-33-1.2.x86-64
1370 # systemd-nspawn -M Fedora-Cloud-Base-33-1.2.x86-64
1371 This downloads an image using machinectl(1) and opens a shell in it.
1373 Example 2. Build and boot a minimal Fedora distribution in a container
1375 # dnf -y --releasever=33 --installroot=/var/lib/machines/f33 \
1377 --disablerepo='*' --enablerepo=fedora --enablerepo=updates install \
1378 systemd passwd dnf fedora-release vim-minimal glibc-minimal-langpack
1379 # systemd-nspawn -bD /var/lib/machines/f33
1380 This installs a minimal Fedora distribution into the directory
1382 /var/lib/machines/f33 and then boots that OS in a namespace container.
1383 Because the installation is located underneath the standard
1384 /var/lib/machines/ directory, it is also possible to start the machine
1385 using systemd-nspawn -M f33.
1386 Example 3. Spawn a shell in a container of a minimal Debian unstable
1388 distribution
1389 # debootstrap unstable ~/debian-tree/
1391 # systemd-nspawn -D ~/debian-tree/
1392 This installs a minimal Debian unstable distribution into the directory
1394 ~/debian-tree/ and then spawns a shell from this image in a namespace
1395 container.
1396 debootstrap supports Debian[7], Ubuntu[8], and Tanglu[9] out of the
1398 box, so the same command can be used to install any of those. For other
1399 distributions from the Debian family, a mirror has to be specified, see
1400 debootstrap(8).
1401 Example 4. Boot a minimal Arch Linux distribution in a container
1403 # pacstrap -c ~/arch-tree/ base
1405 # systemd-nspawn -bD ~/arch-tree/
1406 This installs a minimal Arch Linux distribution into the directory
1408 ~/arch-tree/ and then boots an OS in a namespace container in it.
1409 Example 5. Install the OpenSUSE Tumbleweed rolling distribution
1411 # zypper --root=/var/lib/machines/tumbleweed ar -c \
1413 https://download.opensuse.org/tumbleweed/repo/oss tumbleweed
1414 # zypper --root=/var/lib/machines/tumbleweed refresh
1415 # zypper --root=/var/lib/machines/tumbleweed install --no-recommends \
1416 systemd shadow zypper openSUSE-release vim
1417 # systemd-nspawn -M tumbleweed passwd root
1418 # systemd-nspawn -M tumbleweed -b
1419 Example 6. Boot into an ephemeral snapshot of the host system
1421 # systemd-nspawn -D / -xb
1423 This runs a copy of the host system in a snapshot which is removed
1425 immediately when the container exits. All file system changes made
1426 during runtime will be lost on shutdown, hence.
1427 Example 7. Run a container with SELinux sandbox security contexts
1429 # chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
1431 # systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 \
1432 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh
1433 Example 8. Run a container with an OSTree deployment
1435 # systemd-nspawn -b -i ~/image.raw \
1437 --pivot-root=/ostree/deploy/$OS/deploy/$CHECKSUM:/sysroot \
1438 --bind=+/sysroot/ostree/deploy/$OS/var:/var
1439
1441 The exit code of the program executed in the container is returned.
1442
1444 systemd(1), systemd.nspawn(5), chroot(1), dnf(8), debootstrap(8),
1445 pacman(8), zypper(8), systemd.slice(5), machinectl(1), btrfs(8)
1446
1448 1. Container Interface
1449 https://systemd.io/CONTAINER_INTERFACE
1450 2. Discoverable Partitions Specification
1452 https://systemd.io/DISCOVERABLE_PARTITIONS
1453 3. OCI Runtime Specification
1455 https://github.com/opencontainers/runtime-spec/blob/master/spec.md
1456 4. OSTree
1458 https://ostree.readthedocs.io/en/latest/
1459 5. overlayfs.txt
1461 https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt
1462 6. Fedora
1464 https://getfedora.org
1465 7. Debian
1467 https://www.debian.org
1468 8. Ubuntu
1470 https://www.ubuntu.com
1471 9. Tanglu
1473 https://www.tanglu.org
1474 10. Arch Linux
1476 https://www.archlinux.org
1477 11. OpenSUSE Tumbleweed
1479 https://software.opensuse.org/distributions/tumbleweed
1480systemd 248 SYSTEMD-NSPAWN(1)