portablectl

systemd

portablectl

1

portablectl

Attach, detach or inspect portable service images

portablectl

OPTIONS

COMMAND

NAME

Description

portablectl may be used to attach, detach or inspect portable service images. It's primarily a command interfacing with systemd-portabled.service(8).

Portable service images contain an OS file system tree along with systemd(1) unit file information. A service image may be "attached" to the local system. If attached, a set of unit files are copied from the image to the host, and extended with RootDirectory= or RootImage= assignments (in case of service units) pointing to the image file or directory, ensuring the services will run within the file system context of the image.

Portable service images are an efficient way to bundle multiple related services and other units together, and transfer them as a whole between systems. When these images are attached to the local system, the contained units may run in most ways like regular system-provided units, either with full privileges or inside strict sandboxing, depending on the selected configuration. For more details, see Portable Services.

Portable service images may be of the following kinds:

• Directory trees containing an OS, including the top-level directories /usr/, /etc/, and so on.

• btrfs subvolumes containing OS trees, similar to normal directory trees.

• Binary "raw" disk images containing MBR or GPT partition tables and Linux file system partitions. (These must be regular files, with the .raw suffix.)

Commands

The following commands are understood:

list
List available portable service images. This will list all portable service images discovered in the portable image search paths (see below), along with brief metadata and state information. Note that many of the commands below may both operate on images inside and outside of the search paths. This command is hence mostly a convenience option, the commands are generally not restricted to what this list shows.

attach <IMAGE> [<PREFIX…>]
Attach a portable service image to the host system. Expects a file system path to a portable service image file or directory as first argument. If the specified path contains no slash character (/) it is understood as image filename that is searched for in the portable service image search paths (see below). To reference a file in the current working directory prefix the filename with ./ to avoid this search path logic.

When a portable service is attached four operations are executed:

1. All unit files of types .service, .socket, .target, .timer and .path which match the indicated unit file name prefix are copied from the image to the host's /etc/systemd/system.attached/ directory (or /run/systemd/system.attached/ — depending whether --runtime is specified, see below), which is included in the built-in unit search path of the system service manager.

2. For unit files of type .service a drop-in is added to these copies that adds RootDirectory= or RootImage= settings (see systemd.unit(5) for details), that ensures these services are run within the file system of the originating portable service image.

3. A second drop-in is created: the "profile" drop-in, that may contain additional security settings (and other settings). A number of profiles are available by default but administrators may define their own ones. See below.

4. If the portable service image file is not already in the search path (see below), a symbolic link to it is created in /etc/portables/ or /run/portables/, to make sure it is included in it.

By default, all unit files whose names start with a prefix generated from the image's file name are copied out. Specifically, the prefix is determined from the image file name with any suffix such as .raw removed, truncated at the first occurrence of an underscore character (_), if there is one. The underscore logic is supposed to be used for versioning so that an image file foobar_47.11.raw will result in a unit file matching prefix of foobar. This prefix is then compared with all unit files names contained in the image in the usual directories, but only unit file names where the prefix is followed by -, . or @ are considered. Example: if a portable service image file is named foobar_47.11.raw then by default all its unit files with names such as foobar-quux-waldi.service, foobar.service or foobar@.service will be considered. It's possible to override the matching prefix: all strings listed on the command line after the image file name are considered prefixes, overriding the implicit logic where the prefix is derived from the image file name.

By default, after the unit files are attached the service manager's configuration is reloaded, except when --no-reload is specified (see below). This ensures that the new units made available to the service manager are seen by it.

If --now and/or --enable are passed, the portable services are immediately started (blocking operation unless --no-block is passed) and/or enabled after attaching the image.

When images are attached, an image policy will be generated that pins the attached image by the exact content that was found while attaching, so that it cannot be swapped downgrading security (e.g.: removing dm-verity protection) without a full reinstallation. For more details on policies, see systemd.image-policy(7).

detach <IMAGE> [<PREFIX…>]
Detaches a portable service image from the host. This undoes the operations executed by the attach command above, and removes the unit file copies, drop-ins and image symlink again. This command expects an image name or path as parameter. Note that if a path is specified only the last component of it (i.e. the file or directory name itself, not the path to it) is used for finding matching unit files. This is a convenience feature to allow all arguments passed as attach also to detach.

If --now and/or --enable are passed, the portable services are immediately stopped (blocking operation) and/or disabled before detaching the image. Prefix(es) are also accepted, to be used in case the unit names do not match the image name as described in the attach.

reattach <IMAGE> [<PREFIX…>]
Detaches an existing portable service image from the host, and immediately attaches it again. This is useful in case the image was replaced. Running units are not stopped during the process. Partial matching, to allow for different versions in the image name, is allowed: only the part before the first _ character has to match. If the new image does not exist, the existing one will not be detached. The parameters follow the same syntax as the attach command.

If --now and/or --enable are passed, the portable services are immediately stopped if removed, started and/or enabled if added, or restarted if updated. Prefixes are also accepted, in the same way as described in the attach case.

inspect <IMAGE> [<PREFIX…>]
Extracts various metadata from a portable service image and presents it to the caller. Specifically, the os-release(5) file of the image is retrieved as well as all matching unit files. By default, a short summary showing the most relevant metadata in combination with a list of matching unit files is shown (that is the unit files attach would install to the host system). If combined with --cat (see above), the os-release data and the units files' contents is displayed unprocessed. This command is useful to determine whether an image qualifies as portable service image, and which unit files are included. This command expects the path to the image as parameter, optionally followed by a list of unit file prefixes to consider, similar to the attach command described above.

is-attached <IMAGE>
Determines whether the specified image is currently attached or not. Unless combined with the --quiet switch this will show a short state identifier for the image. Specifically:

Image attachment states

read-only <IMAGE> [<BOOL>]
Marks or (unmarks) a portable service image read-only. Takes an image name, followed by a boolean as arguments. If the boolean is omitted, positive is implied, i.e. the image is marked read-only.

remove <IMAGE>…
Removes one or more portable service images. Note that this command will only remove the specified image path itself — it refers to a symbolic link then the symbolic link is removed and not the image it points to.

set-limit [<IMAGE>] <BYTES>
Sets the maximum size in bytes that a specific portable service image, or all images, may grow up to on disk (disk quota). Takes either one or two parameters. The first, optional parameter refers to a portable service image name. If specified, the size limit of the specified image is changed. If omitted, the overall size limit of the sum of all images stored locally is changed. The final argument specifies the size limit in bytes, possibly suffixed by the usual K, M, G, T units. If the size limit shall be disabled, specify - as size.

Note that per-image size limits are only supported on btrfs file systems. Also, depending on BindPaths= settings in the portable service's unit files directories from the host might be visible in the image environment during runtime which are not affected by this setting, as only the image itself is counted against this limit.

Options

The following options are understood:

-q; --quiet
Suppresses additional informational output while running.

-p <PROFILE>; --profile=PROFILE
When attaching an image, select the profile to use. By default, the default profile is used. Attaching fails if the selected profile does not exist. For details about profiles, see below.

--copy=
When attaching an image, select whether to prefer copying or symlinking of files installed into the host system. Takes one of copy (files will be copied), symlink (to prefer creation of symbolic links), auto for an intermediary mode where security profile drop-ins and images are symlinked while unit files are copied, or mixed (since v256) where security profile drop-ins are symlinked while unit files and images are copied. Note that this option expresses a preference only, in cases where symbolic links cannot be created — for example when the image operated on is a raw disk image, and hence not directly referentiable from the host file system — copying of files is used unconditionally.

--runtime
When specified the unit and drop-in files are placed in /run/systemd/system.attached/ instead of /etc/systemd/system.attached/. Images attached with this option set hence remain attached only until the next reboot, while they are normally attached persistently.

--no-reload
Do not reload the service manager after attaching or detaching a portable service image. Normally the service manager is reloaded to ensure it is aware of added or removed unit files.

--cat
When inspecting portable service images, show the (unprocessed) contents of the metadata files pulled from the image, instead of brief summaries. Specifically, this will show the os-release(5) and unit file contents of the image.

--enable
Immediately enable/disable the portable service after attaching/detaching.

--now
Immediately start/stop/restart the portable service after attaching/before detaching/after upgrading.

--no-block
Do not block waiting for attach --now to complete.

--clean
When detaching ensure the configuration, state, logs, cache, and runtime data directories of the portable service are removed from the host system.

--extension=PATH
Add an additional image <PATH> as an overlay on top of <IMAGE> when attaching/detaching. This argument can be specified multiple times, in which case the order in which images are laid down follows the rules specified in systemd.exec(5) for the ExtensionImages= directive and for the systemd-sysext(8) and systemd-confext(8) tools. The images must contain an extension-release file with metadata that matches what is defined in the os-release of <IMAGE>. See: os-release(5). Images can be block images, btrfs subvolumes or directories. For more information on portable services with extensions, see the Extension Images paragraph on Portable Services.

Note that the same extensions have to be specified, in the same order, when attaching and detaching.

--force
Skip safety checks and attach or detach images (with extensions) without first ensuring that the units are not running, and do not insist that the extension-release.NAME file in the extension image has to match the image filename.

Files and Directories

Portable service images are preferably stored in /var/lib/portables/, but are also searched for in /etc/portables/, /run/portables/, /usr/local/lib/portables/ and /usr/lib/portables/. It's recommended not to place image files directly in /etc/portables/ or /run/portables/ (as these are generally not suitable for storing large or non-textual data), but use these directories only for linking images located elsewhere into the image search path.

When a portable service image is attached, matching unit files are copied onto the host into the /etc/systemd/system.attached/ and /run/systemd/system.attached/ directories. When an image is detached, the unit files are removed again from these directories.

Profiles

When portable service images are attached a "profile" drop-in is linked in, which may be used to enforce additional security (and other) restrictions locally. Four profile drop-ins are defined by default, and shipped in /usr/lib/systemd/portable/profile/. Additional, local profiles may be defined by placing them in /etc/systemd/portable/profile/. The default profiles are:

Profiles

For details on these profiles and their effects see their precise definitions, e.g. /usr/lib/systemd/portable/profile/default/service.conf and similar.

Exit status

On success, 0 is returned, a non-zero failure code otherwise.

See Also

systemd(1), systemd-sysext(8), org.freedesktop.portable1(5), systemd-portabled.service(8), importctl(1)