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. The
32 host's network interfaces and the system clock may not be changed from
33 within the container. Device nodes may not be created. The host system
34 cannot be rebooted and kernel modules may not be loaded from within the
35 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 outside
74 of the container, and their contents will be lost when the container
75 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 --root-hash-sig=
326 Takes a PKCS7 formatted binary signature of the --root-hash= option
327 as a path to a DER encoded signature file or as an ASCII base64
328 string encoding of the DER encoded signature, prefixed by
329 "base64:". The dm-verity volume will only be opened if the
330 signature of the root hash hex string is valid and done by a public
331 key present in the kernel keyring. If this option is not specified,
332 but a file with the .roothash.p7s suffix is found next to the image
333 file, bearing otherwise the same name (except if the image has the
334 .raw suffix, in which case the signature file must not have it in
335 its name), the signature is read from it and automatically used.
336 --verity-data=
338 Takes the path to a data integrity (dm-verity) file. This option
339 enables data integrity checks using dm-verity, if a root-hash is
340 passed and if the used image itself does not contains the integrity
341 data. The integrity data must be matched by the root hash. If this
342 option is not specified, but a file with the .verity suffix is
343 found next to the image file, bearing otherwise the same name
344 (except if the image has the .raw suffix, in which case the verity
345 data file must not have it in its name), the verity data is read
346 from it and automatically used.
347 --pivot-root=
349 Pivot the specified directory to / inside the container, and either
350 unmount the container's old root, or pivot it to another specified
351 directory. Takes one of: a path argument — in which case the
352 specified path will be pivoted to / and the old root will be
353 unmounted; or a colon-separated pair of new root path and pivot
354 destination for the old root. The new root path will be pivoted to
355 /, and the old / will be pivoted to the other directory. Both paths
356 must be absolute, and are resolved in the container's file system
357 namespace.
358 This is for containers which have several bootable directories in
360 them; for example, several OSTree[4] deployments. It emulates the
361 behavior of the boot loader and initial RAM disk which normally
362 select which directory to mount as the root and start the
363 container's PID 1 in.
364 Execution Options
366 -a, --as-pid2
367 Invoke the shell or specified program as process ID (PID) 2 instead
368 of PID 1 (init). By default, if neither this option nor --boot is
369 used, the selected program is run as the process with PID 1, a mode
370 only suitable for programs that are aware of the special semantics
371 that the process with PID 1 has on UNIX. For example, it needs to
372 reap all processes reparented to it, and should implement sysvinit
373 compatible signal handling (specifically: it needs to reboot on
374 SIGINT, reexecute on SIGTERM, reload configuration on SIGHUP, and
375 so on). With --as-pid2 a minimal stub init process is run as PID 1
376 and the selected program is executed as PID 2 (and hence does not
377 need to implement any special semantics). The stub init process
378 will reap processes as necessary and react appropriately to
379 signals. It is recommended to use this mode to invoke arbitrary
380 commands in containers, unless they have been modified to run
381 correctly as PID 1. Or in other words: this switch should be used
382 for pretty much all commands, except when the command refers to an
383 init or shell implementation, as these are generally capable of
384 running correctly as PID 1. This option may not be combined with
385 --boot.
386 -b, --boot
388 Automatically search for an init program and invoke it as PID 1,
389 instead of a shell or a user supplied program. If this option is
390 used, arguments specified on the command line are used as arguments
391 for the init program. This option may not be combined with
392 --as-pid2.
393 The following table explains the different modes of invocation and
395 relationship to --as-pid2 (see above):
396 Table 1. Invocation Mode
398 ┌──────────────────────┬────────────────────────────┐
399 │Switch │ Explanation │
400 ├──────────────────────┼────────────────────────────┤
401 │Neither --as-pid2 nor │ The passed parameters are │
402 │--boot specified │ interpreted as the command │
403 │ │ line, which is executed as │
404 │ │ PID 1 in the container. │
405 ├──────────────────────┼────────────────────────────┤
406 │--as-pid2 specified │ The passed parameters are │
407 │ │ interpreted as the command │
408 │ │ line, which is executed as │
409 │ │ PID 2 in the container. A │
410 │ │ stub init process is run │
411 │ │ as PID 1. │
412 ├──────────────────────┼────────────────────────────┤
413 │--boot specified │ An init program is │
414 │ │ automatically searched for │
415 │ │ and run as PID 1 in the │
416 │ │ container. The passed │
417 │ │ parameters are used as │
418 │ │ invocation parameters for │
419 │ │ this process. │
420 └──────────────────────┴────────────────────────────┘
421 Note that --boot is the default mode of operation if the
422 systemd-nspawn@.service template unit file is used.
423 --chdir=
425 Change to the specified working directory before invoking the
426 process in the container. Expects an absolute path in the
427 container's file system namespace.
428 -E NAME=VALUE, --setenv=NAME=VALUE
430 Specifies an environment variable assignment to pass to the init
431 process in the container, in the format "NAME=VALUE". This may be
432 used to override the default variables or to set additional
433 variables. This parameter may be used more than once.
434 -u, --user=
436 After transitioning into the container, change to the specified
437 user defined in the container's user database. Like all other
438 systemd-nspawn features, this is not a security feature and
439 provides protection against accidental destructive operations only.
440 --kill-signal=
442 Specify the process signal to send to the container's PID 1 when
443 nspawn itself receives SIGTERM, in order to trigger an orderly
444 shutdown of the container. Defaults to SIGRTMIN+3 if --boot is used
445 (on systemd-compatible init systems SIGRTMIN+3 triggers an orderly
446 shutdown). If --boot is not used and this option is not specified
447 the container's processes are terminated abruptly via SIGKILL. For
448 a list of valid signals, see signal(7).
449 --notify-ready=
451 Configures support for notifications from the container's init
452 process. --notify-ready= takes a boolean (no and yes). With option
453 no systemd-nspawn notifies systemd with a "READY=1" message when
454 the init process is created. With option yes systemd-nspawn waits
455 for the "READY=1" message from the init process in the container
456 before sending its own to systemd. For more details about
457 notifications see sd_notify(3).
458 System Identity Options
460 -M, --machine=
461 Sets the machine name for this container. This name may be used to
462 identify this container during its runtime (for example in tools
463 like machinectl(1) and similar), and is used to initialize the
464 container's hostname (which the container can choose to override,
465 however). If not specified, the last component of the root
466 directory path of the container is used, possibly suffixed with a
467 random identifier in case --ephemeral mode is selected. If the root
468 directory selected is the host's root directory the host's hostname
469 is used as default instead.
470 --hostname=
472 Controls the hostname to set within the container, if different
473 from the machine name. Expects a valid hostname as argument. If
474 this option is used, the kernel hostname of the container will be
475 set to this value, otherwise it will be initialized to the machine
476 name as controlled by the --machine= option described above. The
477 machine name is used for various aspect of identification of the
478 container from the outside, the kernel hostname configurable with
479 this option is useful for the container to identify itself from the
480 inside. It is usually a good idea to keep both forms of
481 identification synchronized, in order to avoid confusion. It is
482 hence recommended to avoid usage of this option, and use --machine=
483 exclusively. Note that regardless whether the container's hostname
484 is initialized from the name set with --hostname= or the one set
485 with --machine=, the container can later override its kernel
486 hostname freely on its own as well.
487 --uuid=
489 Set the specified UUID for the container. The init system will
490 initialize /etc/machine-id from this if this file is not set yet.
491 Note that this option takes effect only if /etc/machine-id in the
492 container is unpopulated.
493 Property Options
495 -S, --slice=
496 Make the container part of the specified slice, instead of the
497 default machine.slice. This applies only if the machine is run in
498 its own scope unit, i.e. if --keep-unit isn't used.
499 --property=
501 Set a unit property on the scope unit to register for the machine.
502 This applies only if the machine is run in its own scope unit, i.e.
503 if --keep-unit isn't used. Takes unit property assignments in the
504 same format as systemctl set-property. This is useful to set memory
505 limits and similar for container.
506 --register=
508 Controls whether the container is registered with systemd-
509 machined(8). Takes a boolean argument, which defaults to "yes".
510 This option should be enabled when the container runs a full
511 Operating System (more specifically: a system and service manager
512 as PID 1), and is useful to ensure that the container is accessible
513 via machinectl(1) and shown by tools such as ps(1). If the
514 container does not run a service manager, it is recommended to set
515 this option to "no".
516 --keep-unit
518 Instead of creating a transient scope unit to run the container in,
519 simply use the service or scope unit systemd-nspawn has been
520 invoked in. If --register=yes is set this unit is registered with
521 systemd-machined(8). This switch should be used if systemd-nspawn
522 is invoked from within a service unit, and the service unit's sole
523 purpose is to run a single systemd-nspawn container. This option is
524 not available if run from a user session.
525 Note that passing --keep-unit disables the effect of --slice= and
527 --property=. Use --keep-unit and --register=no in combination to
528 disable any kind of unit allocation or registration with
529 systemd-machined.
530 User Namespacing Options
532 --private-users=
533 Controls user namespacing. If enabled, the container will run with
534 its own private set of UNIX user and group ids (UIDs and GIDs).
535 This involves mapping the private UIDs/GIDs used in the container
536 (starting with the container's root user 0 and up) to a range of
537 UIDs/GIDs on the host that are not used for other purposes (usually
538 in the range beyond the host's UID/GID 65536). The parameter may be
539 specified as follows:
540 1. If one or two colon-separated numbers are specified, user
542 namespacing is turned on. The first parameter specifies the
543 first host UID/GID to assign to the container, the second
544 parameter specifies the number of host UIDs/GIDs to assign to
545 the container. If the second parameter is omitted, 65536
546 UIDs/GIDs are assigned.
547 2. If the parameter is omitted, or true, user namespacing is
549 turned on. The UID/GID range to use is determined automatically
550 from the file ownership of the root directory of the
551 container's directory tree. To use this option, make sure to
552 prepare the directory tree in advance, and ensure that all
553 files and directories in it are owned by UIDs/GIDs in the range
554 you'd like to use. Also, make sure that used file ACLs
555 exclusively reference UIDs/GIDs in the appropriate range. If
556 this mode is used the number of UIDs/GIDs assigned to the
557 container for use is 65536, and the UID/GID of the root
558 directory must be a multiple of 65536.
559 3. If the parameter is false, user namespacing is turned off. This
561 is the default.
562 4. The special value "pick" turns on user namespacing. In this
564 case the UID/GID range is automatically chosen. As first step,
565 the file owner of the root directory of the container's
566 directory tree is read, and it is checked that it is currently
567 not used by the system otherwise (in particular, that no other
568 container is using it). If this check is successful, the
569 UID/GID range determined this way is used, similar to the
570 behavior if "yes" is specified. If the check is not successful
571 (and thus the UID/GID range indicated in the root directory's
572 file owner is already used elsewhere) a new – currently unused
573 – UID/GID range of 65536 UIDs/GIDs is randomly chosen between
574 the host UID/GIDs of 524288 and 1878982656, always starting at
575 a multiple of 65536, and, if possible, consistently hashed from
576 the machine name. This setting implies --private-users-chown
577 (see below), which has the effect that the files and
578 directories in the container's directory tree will be owned by
579 the appropriate users of the range picked. Using this option
580 makes user namespace behavior fully automatic. Note that the
581 first invocation of a previously unused container image might
582 result in picking a new UID/GID range for it, and thus in the
583 (possibly expensive) file ownership adjustment operation.
584 However, subsequent invocations of the container will be cheap
585 (unless of course the picked UID/GID range is assigned to a
586 different use by then).
587 It is recommended to assign at least 65536 UIDs/GIDs to each
589 container, so that the usable UID/GID range in the container covers
590 16 bit. For best security, do not assign overlapping UID/GID ranges
591 to multiple containers. It is hence a good idea to use the upper 16
592 bit of the host 32-bit UIDs/GIDs as container identifier, while the
593 lower 16 bit encode the container UID/GID used. This is in fact the
594 behavior enforced by the --private-users=pick option.
595 When user namespaces are used, the GID range assigned to each
597 container is always chosen identical to the UID range.
598 In most cases, using --private-users=pick is the recommended option
600 as it enhances container security massively and operates fully
601 automatically in most cases.
602 Note that the picked UID/GID range is not written to /etc/passwd or
604 /etc/group. In fact, the allocation of the range is not stored
605 persistently anywhere, except in the file ownership of the files
606 and directories of the container.
607 Note that when user namespacing is used file ownership on disk
609 reflects this, and all of the container's files and directories are
610 owned by the container's effective user and group IDs. This means
611 that copying files from and to the container image requires
612 correction of the numeric UID/GID values, according to the UID/GID
613 shift applied.
614 --private-users-chown
616 If specified, all files and directories in the container's
617 directory tree will be adjusted so that they are owned by the
618 appropriate UIDs/GIDs selected for the container (see above). This
619 operation is potentially expensive, as it involves iterating
620 through the full directory tree of the container. Besides actual
621 file ownership, file ACLs are adjusted as well.
622 This option is implied if --private-users=pick is used. This option
624 has no effect if user namespacing is not used.
625 -U
627 If the kernel supports the user namespaces feature, equivalent to
628 --private-users=pick --private-users-chown, otherwise equivalent to
629 --private-users=no.
630 Note that -U is the default if the systemd-nspawn@.service template
632 unit file is used.
633 Note: it is possible to undo the effect of --private-users-chown
635 (or -U) on the file system by redoing the operation with the first
636 UID of 0:
637 systemd-nspawn ... --private-users=0 --private-users-chown
639 Networking Options
641 --private-network
642 Disconnect networking of the container from the host. This makes
643 all network interfaces unavailable in the container, with the
644 exception of the loopback device and those specified with
645 --network-interface= and configured with --network-veth. If this
646 option is specified, the CAP_NET_ADMIN capability will be added to
647 the set of capabilities the container retains. The latter may be
648 disabled by using --drop-capability=. If this option is not
649 specified (or implied by one of the options listed below), the
650 container will have full access to the host network.
651 --network-interface=
653 Assign the specified network interface to the container. This will
654 remove the specified interface from the calling namespace and place
655 it in the container. When the container terminates, it is moved
656 back to the host namespace. Note that --network-interface= implies
657 --private-network. This option may be used more than once to add
658 multiple network interfaces to the container.
659 --network-macvlan=
661 Create a "macvlan" interface of the specified Ethernet network
662 interface and add it to the container. A "macvlan" interface is a
663 virtual interface that adds a second MAC address to an existing
664 physical Ethernet link. The interface in the container will be
665 named after the interface on the host, prefixed with "mv-". Note
666 that --network-macvlan= implies --private-network. This option may
667 be used more than once to add multiple network interfaces to the
668 container.
669 --network-ipvlan=
671 Create an "ipvlan" interface of the specified Ethernet network
672 interface and add it to the container. An "ipvlan" interface is a
673 virtual interface, similar to a "macvlan" interface, which uses the
674 same MAC address as the underlying interface. The interface in the
675 container will be named after the interface on the host, prefixed
676 with "iv-". Note that --network-ipvlan= implies --private-network.
677 This option may be used more than once to add multiple network
678 interfaces to the container.
679 -n, --network-veth
681 Create a virtual Ethernet link ("veth") between host and container.
682 The host side of the Ethernet link will be available as a network
683 interface named after the container's name (as specified with
684 --machine=), prefixed with "ve-". The container side of the
685 Ethernet link will be named "host0". The --network-veth option
686 implies --private-network.
687 Note that systemd-networkd.service(8) includes by default a network
689 file /usr/lib/systemd/network/80-container-ve.network matching the
690 host-side interfaces created this way, which contains settings to
691 enable automatic address provisioning on the created virtual link
692 via DHCP, as well as automatic IP routing onto the host's external
693 network interfaces. It also contains
694 /usr/lib/systemd/network/80-container-host0.network matching the
695 container-side interface created this way, containing settings to
696 enable client side address assignment via DHCP. In case
697 systemd-networkd is running on both the host and inside the
698 container, automatic IP communication from the container to the
699 host is thus available, with further connectivity to the external
700 network.
701 Note that --network-veth is the default if the
703 systemd-nspawn@.service template unit file is used.
704 Note that on Linux network interface names may have a length of 15
706 characters at maximum, while container names may have a length up
707 to 64 characters. As this option derives the host-side interface
708 name from the container name the name is possibly truncated. Thus,
709 care needs to be taken to ensure that interface names remain unique
710 in this case, or even better container names are generally not
711 chosen longer than 12 characters, to avoid the truncation. If the
712 name is truncated, systemd-nspawn will automatically append a
713 4-digit hash value to the name to reduce the chance of collisions.
714 However, the hash algorithm is not collision-free. (See
715 systemd.net-naming-scheme(7) for details on older naming algorithms
716 for this interface). Alternatively, the --network-veth-extra=
717 option may be used, which allows free configuration of the
718 host-side interface name independently of the container name — but
719 might require a bit more additional configuration in case bridging
720 in a fashion similar to --network-bridge= is desired.
721 --network-veth-extra=
723 Adds an additional virtual Ethernet link between host and
724 container. Takes a colon-separated pair of host interface name and
725 container interface name. The latter may be omitted in which case
726 the container and host sides will be assigned the same name. This
727 switch is independent of --network-veth, and — in contrast — may be
728 used multiple times, and allows configuration of the network
729 interface names. Note that --network-bridge= has no effect on
730 interfaces created with --network-veth-extra=.
731 --network-bridge=
733 Adds the host side of the Ethernet link created with --network-veth
734 to the specified Ethernet bridge interface. Expects a valid network
735 interface name of a bridge device as argument. Note that
736 --network-bridge= implies --network-veth. If this option is used,
737 the host side of the Ethernet link will use the "vb-" prefix
738 instead of "ve-". Regardless of the used naming prefix the same
739 network interface name length limits imposed by Linux apply, along
740 with the complications this creates (for details see above).
741 --network-zone=
743 Creates a virtual Ethernet link ("veth") to the container and adds
744 it to an automatically managed Ethernet bridge interface. The
745 bridge interface is named after the passed argument, prefixed with
746 "vz-". The bridge interface is automatically created when the first
747 container configured for its name is started, and is automatically
748 removed when the last container configured for its name exits.
749 Hence, each bridge interface configured this way exists only as
750 long as there's at least one container referencing it running. This
751 option is very similar to --network-bridge=, besides this automatic
752 creation/removal of the bridge device.
753 This setting makes it easy to place multiple related containers on
755 a common, virtual Ethernet-based broadcast domain, here called a
756 "zone". Each container may only be part of one zone, but each zone
757 may contain any number of containers. Each zone is referenced by
758 its name. Names may be chosen freely (as long as they form valid
759 network interface names when prefixed with "vz-"), and it is
760 sufficient to pass the same name to the --network-zone= switch of
761 the various concurrently running containers to join them in one
762 zone.
763 Note that systemd-networkd.service(8) includes by default a network
765 file /usr/lib/systemd/network/80-container-vz.network matching the
766 bridge interfaces created this way, which contains settings to
767 enable automatic address provisioning on the created virtual
768 network via DHCP, as well as automatic IP routing onto the host's
769 external network interfaces. Using --network-zone= is hence in most
770 cases fully automatic and sufficient to connect multiple local
771 containers in a joined broadcast domain to the host, with further
772 connectivity to the external network.
773 --network-namespace-path=
775 Takes the path to a file representing a kernel network namespace
776 that the container shall run in. The specified path should refer to
777 a (possibly bind-mounted) network namespace file, as exposed by the
778 kernel below /proc/$PID/ns/net. This makes the container enter the
779 given network namespace. One of the typical use cases is to give a
780 network namespace under /run/netns created by ip-netns(8), for
781 example, --network-namespace-path=/run/netns/foo. Note that this
782 option cannot be used together with other network-related options,
783 such as --private-network or --network-interface=.
784 -p, --port=
786 If private networking is enabled, maps an IP port on the host onto
787 an IP port on the container. Takes a protocol specifier (either
788 "tcp" or "udp"), separated by a colon from a host port number in
789 the range 1 to 65535, separated by a colon from a container port
790 number in the range from 1 to 65535. The protocol specifier and its
791 separating colon may be omitted, in which case "tcp" is assumed.
792 The container port number and its colon may be omitted, in which
793 case the same port as the host port is implied. This option is only
794 supported if private networking is used, such as with
795 --network-veth, --network-zone= --network-bridge=.
796 Security Options
798 --capability=
799 List one or more additional capabilities to grant the container.
800 Takes a comma-separated list of capability names, see
801 capabilities(7) for more information. Note that the following
802 capabilities will be granted in any way: CAP_AUDIT_CONTROL,
803 CAP_AUDIT_WRITE, CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
804 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER, CAP_KILL, CAP_LEASE,
805 CAP_LINUX_IMMUTABLE, CAP_MKNOD, CAP_NET_BIND_SERVICE,
806 CAP_NET_BROADCAST, CAP_NET_RAW, CAP_SETFCAP, CAP_SETGID,
807 CAP_SETPCAP, CAP_SETUID, CAP_SYS_ADMIN, CAP_SYS_BOOT,
808 CAP_SYS_CHROOT, CAP_SYS_NICE, CAP_SYS_PTRACE, CAP_SYS_RESOURCE,
809 CAP_SYS_TTY_CONFIG. Also CAP_NET_ADMIN is retained if
810 --private-network is specified. If the special value "all" is
811 passed, all capabilities are retained.
812 If the special value of "help" is passed, the program will print
814 known capability names and exit.
815 --drop-capability=
817 Specify one or more additional capabilities to drop for the
818 container. This allows running the container with fewer
819 capabilities than the default (see above).
820 If the special value of "help" is passed, the program will print
822 known capability names and exit.
823 --no-new-privileges=
825 Takes a boolean argument. Specifies the value of the
826 PR_SET_NO_NEW_PRIVS flag for the container payload. Defaults to
827 off. When turned on the payload code of the container cannot
828 acquire new privileges, i.e. the "setuid" file bit as well as file
829 system capabilities will not have an effect anymore. See prctl(2)
830 for details about this flag.
831 --system-call-filter=
833 Alter the system call filter applied to containers. Takes a
834 space-separated list of system call names or group names (the
835 latter prefixed with "@", as listed by the syscall-filter command
836 of systemd-analyze(1)). Passed system calls will be permitted. The
837 list may optionally be prefixed by "~", in which case all listed
838 system calls are prohibited. If this command line option is used
839 multiple times the configured lists are combined. If both a
840 positive and a negative list (that is one system call list without
841 and one with the "~" prefix) are configured, the negative list
842 takes precedence over the positive list. Note that systemd-nspawn
843 always implements a system call allow list (as opposed to a deny
844 list!), and this command line option hence adds or removes entries
845 from the default allow list, depending on the "~" prefix. Note that
846 the applied system call filter is also altered implicitly if
847 additional capabilities are passed using the --capabilities=.
848 -Z, --selinux-context=
850 Sets the SELinux security context to be used to label processes in
851 the container.
852 -L, --selinux-apifs-context=
854 Sets the SELinux security context to be used to label files in the
855 virtual API file systems in the container.
856 Resource Options
858 --rlimit=
859 Sets the specified POSIX resource limit for the container payload.
860 Expects an assignment of the form "LIMIT=SOFT:HARD" or
861 "LIMIT=VALUE", where LIMIT should refer to a resource limit type,
862 such as RLIMIT_NOFILE or RLIMIT_NICE. The SOFT and HARD fields
863 should refer to the numeric soft and hard resource limit values. If
864 the second form is used, VALUE may specify a value that is used
865 both as soft and hard limit. In place of a numeric value the
866 special string "infinity" may be used to turn off resource limiting
867 for the specific type of resource. This command line option may be
868 used multiple times to control limits on multiple limit types. If
869 used multiple times for the same limit type, the last use wins. For
870 details about resource limits see setrlimit(2). By default resource
871 limits for the container's init process (PID 1) are set to the same
872 values the Linux kernel originally passed to the host init system.
873 Note that some resource limits are enforced on resources counted
874 per user, in particular RLIMIT_NPROC. This means that unless user
875 namespacing is deployed (i.e. --private-users= is used, see
876 above), any limits set will be applied to the resource usage of the
877 same user on all local containers as well as the host. This means
878 particular care needs to be taken with these limits as they might
879 be triggered by possibly less trusted code. Example:
880 "--rlimit=RLIMIT_NOFILE=8192:16384".
881 --oom-score-adjust=
883 Changes the OOM ("Out Of Memory") score adjustment value for the
884 container payload. This controls /proc/self/oom_score_adj which
885 influences the preference with which this container is terminated
886 when memory becomes scarce. For details see proc(5). Takes an
887 integer in the range -1000...1000.
888 --cpu-affinity=
890 Controls the CPU affinity of the container payload. Takes a comma
891 separated list of CPU numbers or number ranges (the latter's start
892 and end value separated by dashes). See sched_setaffinity(2) for
893 details.
894 --personality=
896 Control the architecture ("personality") reported by uname(2) in
897 the container. Currently, only "x86" and "x86-64" are supported.
898 This is useful when running a 32-bit container on a 64-bit host. If
899 this setting is not used, the personality reported in the container
900 is the same as the one reported on the host.
901 Integration Options
903 --resolv-conf=
904 Configures how /etc/resolv.conf inside of the container shall be
905 handled (i.e. DNS configuration synchronization from host to
906 container). Takes one of "off", "copy-host", "copy-static",
907 "copy-uplink", "copy-stub", "replace-host", "replace-static",
908 "replace-uplink", "replace-stub", "bind-host", "bind-static",
909 "bind-uplink", "bind-stub", "delete" or "auto".
910 If set to "off" the /etc/resolv.conf file in the container is left
912 as it is included in the image, and neither modified nor bind
913 mounted over.
914 If set to "copy-host", the /etc/resolv.conf file from the host is
916 copied into the container, unless the file exists already and is
917 not a regular file (e.g. a symlink). Similar, if "replace-host" is
918 used the file is copied, replacing any existing inode, including
919 symlinks. Similar, if "bind-host" is used, the file is bind mounted
920 from the host into the container.
921 If set to "copy-static", "replace-static" or "bind-static" the
923 static resolv.conf file supplied with systemd-resolved.service(8)
924 (specifically: /usr/lib/systemd/resolv.conf) is copied or bind
925 mounted into the container.
926 If set to "copy-uplink", "replace-uplink" or "bind-uplink" the
928 uplink resolv.conf file managed by systemd-resolved.service
929 (specifically: /run/systemd/resolve/resolv.conf) is copied or bind
930 mounted into the container.
931 If set to "copy-stub", "replace-stub" or "bind-stub" the stub
933 resolv.conf file managed by systemd-resolved.service (specifically:
934 /run/systemd/resolve/stub-resolv.conf) is copied or bind mounted
935 into the container.
936 If set to "delete" the /etc/resolv.conf file in the container is
938 deleted if it exists.
939 Finally, if set to "auto" the file is left as it is if private
941 networking is turned on (see --private-network). Otherwise, if
942 systemd-resolved.service is running its stub resolv.conf file is
943 used, and if not the host's /etc/resolv.conf file. In the latter
944 cases the file is copied if the image is writable, and bind mounted
945 otherwise.
946 It's recommended to use "copy-..." or "replace-..." if the
948 container shall be able to make changes to the DNS configuration on
949 its own, deviating from the host's settings. Otherwise "bind" is
950 preferable, as it means direct changes to /etc/resolv.conf in the
951 container are not allowed, as it is a read-only bind mount (but
952 note that if the container has enough privileges, it might simply
953 go ahead and unmount the bind mount anyway). Note that both if the
954 file is bind mounted and if it is copied no further propagation of
955 configuration is generally done after the one-time early
956 initialization (this is because the file is usually updated through
957 copying and renaming). Defaults to "auto".
958 --timezone=
960 Configures how /etc/localtime inside of the container (i.e. local
961 timezone synchronization from host to container) shall be handled.
962 Takes one of "off", "copy", "bind", "symlink", "delete" or "auto".
963 If set to "off" the /etc/localtime file in the container is left as
964 it is included in the image, and neither modified nor bind mounted
965 over. If set to "copy" the /etc/localtime file of the host is
966 copied into the container. Similarly, if "bind" is used, the file
967 is bind mounted from the host into the container. If set to
968 "symlink", a symlink is created pointing from /etc/localtime in the
969 container to the timezone file in the container that matches the
970 timezone setting on the host. If set to "delete", the file in the
971 container is deleted, should it exist. If set to "auto" and the
972 /etc/localtime file of the host is a symlink, then "symlink" mode
973 is used, and "copy" otherwise, except if the image is read-only in
974 which case "bind" is used instead. Defaults to "auto".
975 --link-journal=
977 Control whether the container's journal shall be made visible to
978 the host system. If enabled, allows viewing the container's journal
979 files from the host (but not vice versa). Takes one of "no",
980 "host", "try-host", "guest", "try-guest", "auto". If "no", the
981 journal is not linked. If "host", the journal files are stored on
982 the host file system (beneath /var/log/journal/machine-id) and the
983 subdirectory is bind-mounted into the container at the same
984 location. If "guest", the journal files are stored on the guest
985 file system (beneath /var/log/journal/machine-id) and the
986 subdirectory is symlinked into the host at the same location.
987 "try-host" and "try-guest" do the same but do not fail if the host
988 does not have persistent journaling enabled. If "auto" (the
989 default), and the right subdirectory of /var/log/journal exists, it
990 will be bind mounted into the container. If the subdirectory does
991 not exist, no linking is performed. Effectively, booting a
992 container once with "guest" or "host" will link the journal
993 persistently if further on the default of "auto" is used.
994 Note that --link-journal=try-guest is the default if the
996 systemd-nspawn@.service template unit file is used.
997 -j
999 Equivalent to --link-journal=try-guest.
1000 Mount Options
1002 --bind=, --bind-ro=
1003 Bind mount a file or directory from the host into the container.
1004 Takes one of: a path argument — in which case the specified path
1005 will be mounted from the host to the same path in the container, or
1006 a colon-separated pair of paths — in which case the first specified
1007 path is the source in the host, and the second path is the
1008 destination in the container, or a colon-separated triple of source
1009 path, destination path and mount options. The source path may
1010 optionally be prefixed with a "+" character. If so, the source path
1011 is taken relative to the image's root directory. This permits
1012 setting up bind mounts within the container image. The source path
1013 may be specified as empty string, in which case a temporary
1014 directory below the host's /var/tmp directory is used. It is
1015 automatically removed when the container is shut down. Mount
1016 options are comma-separated and currently, only rbind and norbind
1017 are allowed, controlling whether to create a recursive or a regular
1018 bind mount. Defaults to "rbind". Backslash escapes are interpreted,
1019 so "\:" may be used to embed colons in either path. This option may
1020 be specified multiple times for creating multiple independent bind
1021 mount points. The --bind-ro= option creates read-only bind mounts.
1022 Note that when this option is used in combination with
1024 --private-users, the resulting mount points will be owned by the
1025 nobody user. That's because the mount and its files and directories
1026 continue to be owned by the relevant host users and groups, which
1027 do not exist in the container, and thus show up under the wildcard
1028 UID 65534 (nobody). If such bind mounts are created, it is
1029 recommended to make them read-only, using --bind-ro=.
1030 --inaccessible=
1032 Make the specified path inaccessible in the container. This
1033 over-mounts the specified path (which must exist in the container)
1034 with a file node of the same type that is empty and has the most
1035 restrictive access mode supported. This is an effective way to mask
1036 files, directories and other file system objects from the container
1037 payload. This option may be used more than once in case all
1038 specified paths are masked.
1039 --tmpfs=
1041 Mount a tmpfs file system into the container. Takes a single
1042 absolute path argument that specifies where to mount the tmpfs
1043 instance to (in which case the directory access mode will be chosen
1044 as 0755, owned by root/root), or optionally a colon-separated pair
1045 of path and mount option string that is used for mounting (in which
1046 case the kernel default for access mode and owner will be chosen,
1047 unless otherwise specified). Backslash escapes are interpreted in
1048 the path, so "\:" may be used to embed colons in the path.
1049 Note that this option cannot be used to replace the root file
1051 system of the container with a temporary file system. However, the
1052 --volatile= option described below provides similar functionality,
1053 with a focus on implementing stateless operating system images.
1054 --overlay=, --overlay-ro=
1056 Combine multiple directory trees into one overlay file system and
1057 mount it into the container. Takes a list of colon-separated paths
1058 to the directory trees to combine and the destination mount point.
1059 Backslash escapes are interpreted in the paths, so "\:" may be used
1061 to embed colons in the paths.
1062 If three or more paths are specified, then the last specified path
1064 is the destination mount point in the container, all paths
1065 specified before refer to directory trees on the host and are
1066 combined in the specified order into one overlay file system. The
1067 left-most path is hence the lowest directory tree, the
1068 second-to-last path the highest directory tree in the stacking
1069 order. If --overlay-ro= is used instead of --overlay=, a read-only
1070 overlay file system is created. If a writable overlay file system
1071 is created, all changes made to it are written to the highest
1072 directory tree in the stacking order, i.e. the second-to-last
1073 specified.
1074 If only two paths are specified, then the second specified path is
1076 used both as the top-level directory tree in the stacking order as
1077 seen from the host, as well as the mount point for the overlay file
1078 system in the container. At least two paths have to be specified.
1079 The source paths may optionally be prefixed with "+" character. If
1081 so they are taken relative to the image's root directory. The
1082 uppermost source path may also be specified as empty string, in
1083 which case a temporary directory below the host's /var/tmp is used.
1084 The directory is removed automatically when the container is shut
1085 down. This behaviour is useful in order to make read-only container
1086 directories writable while the container is running. For example,
1087 use the "--overlay=+/var::/var" option in order to automatically
1088 overlay a writable temporary directory on a read-only /var
1089 directory.
1090 For details about overlay file systems, see overlayfs.txt[5]. Note
1092 that the semantics of overlay file systems are substantially
1093 different from normal file systems, in particular regarding
1094 reported device and inode information. Device and inode information
1095 may change for a file while it is being written to, and processes
1096 might see out-of-date versions of files at times. Note that this
1097 switch automatically derives the "workdir=" mount option for the
1098 overlay file system from the top-level directory tree, making it a
1099 sibling of it. It is hence essential that the top-level directory
1100 tree is not a mount point itself (since the working directory must
1101 be on the same file system as the top-most directory tree). Also
1102 note that the "lowerdir=" mount option receives the paths to stack
1103 in the opposite order of this switch.
1104 Note that this option cannot be used to replace the root file
1106 system of the container with an overlay file system. However, the
1107 --volatile= option described above provides similar functionality,
1108 with a focus on implementing stateless operating system images.
1109 Input/Output Options
1111 --console=MODE
1112 Configures how to set up standard input, output and error output
1113 for the container payload, as well as the /dev/console device for
1114 the container. Takes one of interactive, read-only, passive, or
1115 pipe. If interactive, a pseudo-TTY is allocated and made available
1116 as /dev/console in the container. It is then bi-directionally
1117 connected to the standard input and output passed to
1118 systemd-nspawn. read-only is similar but only the output of the
1119 container is propagated and no input from the caller is read. If
1120 passive, a pseudo TTY is allocated, but it is not connected
1121 anywhere. Finally, in pipe mode no pseudo TTY is allocated, but the
1122 standard input, output and error output file descriptors passed to
1123 systemd-nspawn are passed on — as they are — to the container
1124 payload, see the following paragraph. Defaults to interactive if
1125 systemd-nspawn is invoked from a terminal, and read-only otherwise.
1126 In pipe mode, /dev/console will not exist in the container. This
1128 means that the container payload generally cannot be a full init
1129 system as init systems tend to require /dev/console to be
1130 available. On the other hand, in this mode container invocations
1131 can be used within shell pipelines. This is because intermediary
1132 pseudo TTYs do not permit independent bidirectional propagation of
1133 the end-of-file (EOF) condition, which is necessary for shell
1134 pipelines to work correctly. Note that the pipe mode should be
1135 used carefully, as passing arbitrary file descriptors to less
1136 trusted container payloads might open up unwanted interfaces for
1137 access by the container payload. For example, if a passed file
1138 descriptor refers to a TTY of some form, APIs such as TIOCSTI may
1139 be used to synthesize input that might be used for escaping the
1140 container. Hence pipe mode should only be used if the payload is
1141 sufficiently trusted or when the standard input/output/error output
1142 file descriptors are known safe, for example pipes.
1143 --pipe, -P
1145 Equivalent to --console=pipe.
1146 --no-pager
1148 Do not pipe output into a pager.
1149 -h, --help
1151 Print a short help text and exit.
1152 --version
1154 Print a short version string and exit.
1155
1157 $SYSTEMD_PAGER
1158 Pager to use when --no-pager is not given; overrides $PAGER. If
1159 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
1160 pager implementations are tried in turn, including less(1) and
1161 more(1), until one is found. If no pager implementation is
1162 discovered no pager is invoked. Setting this environment variable
1163 to an empty string or the value "cat" is equivalent to passing
1164 --no-pager.
1165 $SYSTEMD_LESS
1167 Override the options passed to less (by default "FRSXMK").
1168 Users might want to change two options in particular:
1170 K
1172 This option instructs the pager to exit immediately when Ctrl+C
1173 is pressed. To allow less to handle Ctrl+C itself to switch
1174 back to the pager command prompt, unset this option.
1175 If the value of $SYSTEMD_LESS does not include "K", and the
1177 pager that is invoked is less, Ctrl+C will be ignored by the
1178 executable, and needs to be handled by the pager.
1179 X
1181 This option instructs the pager to not send termcap
1182 initialization and deinitialization strings to the terminal. It
1183 is set by default to allow command output to remain visible in
1184 the terminal even after the pager exits. Nevertheless, this
1185 prevents some pager functionality from working, in particular
1186 paged output cannot be scrolled with the mouse.
1187 See less(1) for more discussion.
1189 $SYSTEMD_LESSCHARSET
1191 Override the charset passed to less (by default "utf-8", if the
1192 invoking terminal is determined to be UTF-8 compatible).
1193 $SYSTEMD_PAGERSECURE
1195 Takes a boolean argument. When true, the "secure" mode of the pager
1196 is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set
1197 at all, secure mode is enabled if the effective UID is not the same
1198 as the owner of the login session, see geteuid(2) and
1199 sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set
1200 when invoking the pager, and the pager shall disable commands that
1201 open or create new files or start new subprocesses. When
1202 $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known
1203 to implement secure mode will not be used. (Currently only less(1)
1204 implements secure mode.)
1205 Note: when commands are invoked with elevated privileges, for
1207 example under sudo(8) or pkexec(1), care must be taken to ensure
1208 that unintended interactive features are not enabled. "Secure" mode
1209 for the pager may be enabled automatically as describe above.
1210 Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited
1211 environment allows the user to invoke arbitrary commands. Note that
1212 if the $SYSTEMD_PAGER or $PAGER variables are to be honoured,
1213 $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
1214 completly disable the pager using --no-pager instead.
1215 $SYSTEMD_COLORS
1217 The value must be a boolean. Controls whether colorized output
1218 should be generated. This can be specified to override the decision
1219 that systemd makes based on $TERM and what the console is connected
1220 to.
1221 $SYSTEMD_URLIFY
1223 The value must be a boolean. Controls whether clickable links
1224 should be generated in the output for terminal emulators supporting
1225 this. This can be specified to override the decision that systemd
1226 makes based on $TERM and other conditions.
1227
1229 Example 1. Download a Fedora image and start a shell in it
1230 # machinectl pull-raw --verify=no \
1232 https://download.fedoraproject.org/pub/fedora/linux/releases/33/Cloud/x86_64/images/Fedora-Cloud-Base-33-1.2.x86_64.raw.xz \
1233 Fedora-Cloud-Base-33-1.2.x86-64
1234 # systemd-nspawn -M Fedora-Cloud-Base-33-1.2.x86-64
1235 This downloads an image using machinectl(1) and opens a shell in it.
1237 Example 2. Build and boot a minimal Fedora distribution in a container
1239 # dnf -y --releasever=33 --installroot=/var/lib/machines/f33 \
1241 --disablerepo='*' --enablerepo=fedora --enablerepo=updates install \
1242 systemd passwd dnf fedora-release vim-minimal glibc-minimal-langpack
1243 # systemd-nspawn -bD /var/lib/machines/f33
1244 This installs a minimal Fedora distribution into the directory
1246 /var/lib/machines/f33 and then boots that OS in a namespace container.
1247 Because the installation is located underneath the standard
1248 /var/lib/machines/ directory, it is also possible to start the machine
1249 using systemd-nspawn -M f33.
1250 Example 3. Spawn a shell in a container of a minimal Debian unstable
1252 distribution
1253 # debootstrap unstable ~/debian-tree/
1255 # systemd-nspawn -D ~/debian-tree/
1256 This installs a minimal Debian unstable distribution into the directory
1258 ~/debian-tree/ and then spawns a shell from this image in a namespace
1259 container.
1260 debootstrap supports Debian[7], Ubuntu[8], and Tanglu[9] out of the
1262 box, so the same command can be used to install any of those. For other
1263 distributions from the Debian family, a mirror has to be specified, see
1264 debootstrap(8).
1265 Example 4. Boot a minimal Arch Linux distribution in a container
1267 # pacstrap -c ~/arch-tree/ base
1269 # systemd-nspawn -bD ~/arch-tree/
1270 This installs a minimal Arch Linux distribution into the directory
1272 ~/arch-tree/ and then boots an OS in a namespace container in it.
1273 Example 5. Install the OpenSUSE Tumbleweed rolling distribution
1275 # zypper --root=/var/lib/machines/tumbleweed ar -c \
1277 https://download.opensuse.org/tumbleweed/repo/oss tumbleweed
1278 # zypper --root=/var/lib/machines/tumbleweed refresh
1279 # zypper --root=/var/lib/machines/tumbleweed install --no-recommends \
1280 systemd shadow zypper openSUSE-release vim
1281 # systemd-nspawn -M tumbleweed passwd root
1282 # systemd-nspawn -M tumbleweed -b
1283 Example 6. Boot into an ephemeral snapshot of the host system
1285 # systemd-nspawn -D / -xb
1287 This runs a copy of the host system in a snapshot which is removed
1289 immediately when the container exits. All file system changes made
1290 during runtime will be lost on shutdown, hence.
1291 Example 7. Run a container with SELinux sandbox security contexts
1293 # chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
1295 # systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 \
1296 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh
1297 Example 8. Run a container with an OSTree deployment
1299 # systemd-nspawn -b -i ~/image.raw \
1301 --pivot-root=/ostree/deploy/$OS/deploy/$CHECKSUM:/sysroot \
1302 --bind=+/sysroot/ostree/deploy/$OS/var:/var
1303
1305 The exit code of the program executed in the container is returned.
1306
1308 systemd(1), systemd.nspawn(5), chroot(1), dnf(8), debootstrap(8),
1309 pacman(8), zypper(8), systemd.slice(5), machinectl(1), btrfs(8)
1310
1312 1. Container Interface
1313 https://systemd.io/CONTAINER_INTERFACE
1314 2. Discoverable Partitions Specification
1316 https://systemd.io/DISCOVERABLE_PARTITIONS
1317 3. OCI Runtime Specification
1319 https://github.com/opencontainers/runtime-spec/blob/master/spec.md
1320 4. OSTree
1322 https://ostree.readthedocs.io/en/latest/
1323 5. overlayfs.txt
1325 https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt
1326 6. Fedora
1328 https://getfedora.org
1329 7. Debian
1331 https://www.debian.org
1332 8. Ubuntu
1334 https://www.ubuntu.com
1335 9. Tanglu
1337 https://www.tanglu.org
1338 10. Arch Linux
1340 https://www.archlinux.org
1341 11. OpenSUSE Tumbleweed
1343 https://software.opensuse.org/distributions/tumbleweed
1344systemd 246 SYSTEMD-NSPAWN(1)