homectl

systemd
homectl 1
homectl Create, remove, change or inspect home directories
`homectl` OPTIONS COMMAND NAME

## Description

`homectl` may be used to create, remove, change or inspect a user's home directory. It's primarily a command interfacing with systemd-homed.service 8 which manages home directories of users.

Home directories managed by `systemd-homed.service` are self-contained, and thus include the user's full metadata record in the home's data storage itself, making them easy to migrate between machines. In particular, a home directory describes a matching user record, and every user record managed by `systemd-homed.service` also implies existence and encapsulation of a home directory. The user account and home directory become the same concept.

The following backing storage mechanisms are supported:

- An individual LUKS2 encrypted loopback file for a user, stored in `/home/*.home`. At login the file system contained in this files is mounted, after the LUKS2 encrypted volume has been attached. The user's password is identical to the encryption passphrase of the LUKS2 volume. Access to data without preceeding user authentication is thus not possible, even for the system administrator. This storage mechanism provides the strongest data security and is thus recommended.

- Similar, but the LUKS2 encrypted file system is located on regular block device, such as an USB storage stick. In this mode home directories and all data they include are nicely migratable between machines, simply by plugging the USB stick into different systems at different times.

- An encrypted directory using `fscrypt` on file systems that support it (at the moment this is primarily `ext4`), located in `/home/*.homedir`. This mechanism also provides encryption, but substantially weaker than LUKS2, as most file system metadata is unprotected. Moreover it currently does not support changing user passwords once the home directory has been created.

- A `btrfs` subvolume for each user, also located in `/home/*.homedir`. This provides no encryption, but good quota support.

- A regular directory for each user, also located in `/home/*.homedir`. This provides no encryption, but is a suitable fallback available on all machines, even where LUKS2, `fscrypt` or `btrfs` support is not available.

- An individual Windows file share (CIFS) for each user.

Note that `systemd-homed.service` and `homectl` will not manage "classic" UNIX user accounts as created with useradd 8 or similar tools. In particular, this functionality is not suitable for managing system users (i.e. users with a UID below 1000) but is exclusive to regular ("human") users.

Note that users/home directories managed via `systemd-homed.service` do not show up in `/etc/passwd` and similar files, they are synthesized via glibc NSS during runtime. They are thus resolvable and may be enumerated via the getent 1 tool.

This tool interfaces directly with `systemd-homed.service`, and may execute specific commands on the home directories it manages. Since every home directory managed that way also defines a JSON user and group record these home directories may also be inspected and enumerated via userdbctl 1.

Home directories managed by `systemd-homed.service` are usually in one of two states, or in a transition state between them: when `active` they are unlocked and mounted, and thus accessible to the system and its programs; when `inactive` they are not mounted and thus not accessible. Activation happens automatically at login of the user and usually can only complete after a password (or other authentication token) has been supplied. Deactivation happens after the user fully logged out. A home directory remains active as long as the user is logged in at least once, i.e. has at least one login session. When the user logs in a second time simultaneously the home directory remains active. It is deactivated only after the last of the user's sessions ends.

## Options

The following general options are understood (further options that control the various properties of user records managed by `systemd-homed.service` are documented further down):

`--identity=`FILE

  Read the user's JSON record from the specified file. If passed as `-` reads the user record from standard input. The supplied JSON object must follow the structure documented on JSON User Records. This option may be used in conjunction with the `create` and `update` commands (see below), where it allows configuring the user record in JSON as-is, instead of setting the individual user record properties (see below).

`--json=`FORMAT
`-J`

  Controls whether to output the user record in JSON format, if the `inspect` command (see below) is used. Takes one of `pretty`, `short` or `off`. If `pretty` human-friendly whitespace and newlines are inserted in the output to make the JSON data more readable. If `short` all superfluous whitespace is suppressed. If `off` (the default) the user information is not shown in JSON format but in a friendly human readable formatting instead. The `-J` option picks `pretty` when run interactively and `short` otherwise.

`--export-format=`FORMAT
`-E`
`-EE`

  When used with the `inspect` verb in JSON mode (see above) may be used to suppress certain aspects of the JSON user record on output. Specifically, if `stripped` format is used the binding and runtime fields of the record are removed. If `minimal` format is used the cryptographic signature is removed too. If `full` format is used the full JSON record is shown (this is the default). This option is useful for copying an existing user record to a different system in order to create a similar user there with the same settings. Specifically: `homectl inspect -EE | ssh root@othersystem homectl create -i-` may be used as simple command line for replicating a user on another host. `-E` is equivalent to `-j --export-format=stripped`, `-EE` to `-j --export-format=minimal`. Note that when replicating user accounts user records acquired in `stripped` mode will retain the original cryptographic signatures and thus may only be modified when the private key to update them is available on the destination machine. When replicating users in `minimal` mode, the signature is removed during the replication and thus the record will be implicitly signed with the key of the destination machine and may be updated there without any private key replication.

## User Record Properties

The following options control various properties of the user records/home directories that `systemd-homed.service` manages. These switches may be used in conjunction with the `create` and `update` commands for configuring various aspects of the home directory and the user account:

`--real-name=`NAME
`-c` NAME

  The real name for the user. This corresponds with the GECOS field on classic UNIX NSS records.

`--realm=`REALM

  The realm for the user. The realm associates a user with a specific organization or installation, and allows distuingishing users of the same name defined in different contexts. The realm can be any string that also qualifies as valid DNS domain name, and it is recommended to use the organization's or installation's domain name for this purpose, but this is not enforced nor required. On each system only a single user of the same name may exist, and if a user with the same name and realm is seen it is assumed to refer to the same user while a user with the same name but different realm is considered a different user. Note that this means that two users sharing the same name but with distinct realms are not allowed on the same system. Assigning a realm to a user is optional.

`--email-address=`EMAIL

  Takes an electronic mail address to associate with the user. On log-in the `$EMAIL` environment variable is initialized from this value.

`--location=`TEXT

  Takes location specification for this user. This is free-form text, which might or might not be usable by geo-location applications. Example: `--location="Berlin, Germany"` or `--location="Basement, Room 3a"`

`--icon-name=`ICON

  Takes an icon name to associate with the user, following the scheme defined by the Icon Naming Specification.

`--home-dir=`PATH
`-d` PATH

  Takes a path to use as home directory for the user. Note that this is the directory the user's home directory is mounted to while the user is logged in. This is not where the user's data is actually stored, see `--image-path=` for that. If not specified defaults to `/home/$USER`.

`--uid=`UID

  Takes a preferred numeric UNIX UID to assign this user. If a user is to be created with the specified UID and it is already taken by a different user on the local system then creation of the home directory is refused. Note though, if after creating the home directory it is used on a different system and the configured UID is taken by another user there, then `systemd-homed` may assign the user a different UID on that system. The specified UID must be outside of the system user range. It is recommended to use the 60001…60513 UID range for this purpose. If not specified the UID is automatically picked. When logging in and the home directory is found to be owned by a UID not matching the user's assigned one the home directory and all files and directories inside it will have their ownership changed automatically before login completes.

  Note that users managed by `systemd-homed` always have a matching group associated with the same name as well as a GID matching the UID of the user. Thus, configuring the GID separately is not permitted.

`--member-of=`GROUP
`-G` GROUP

  Takes a comma-separated list of auxiliary UNIX groups this user shall belong to. Example: `--member-of=wheel` to provide the user with administrator privileges. Note that `systemd-homed` does not manage any groups besides a group matching the user in name and numeric UID/GID. Thus any groups listed here must be registered independently, for example with groupadd 8. If non-existant groups that are listed there are ignored. This option may be used more than once, in which case all specified group lists are combined.

`--skel=`PATH

  Takes a file system path to a directory. Specifies the skeleton directory to initialize the home directory with. All files and directories in the specified are copied into any newly create home directory. If not specified defaults to `/etc/skel/`.

`--shell=`SHELL

  Takes a file system path. Specifies the shell binary to execute on terminal logins. If not specified defaults to `/bin/bash`.

`--setenv=`VARIABLE=VALUE

  Takes an environment variable assignment to set for all user processes. Note that a number of other settings also result in environment variables to be set for the user, including `--email=`, `--timezone=` and `--language=`. May be used multiple times to set multiple environment variables.

`--timezone=`TIMEZONE

  Takes a timezone specification as string that sets the timezone for the specified user. Expects a `tzdata` location string. When the user logs in the `$TZ` environment variable is initialized from this setting. Example: `--timezone=Europe/Amsterdam` will result in the environment variable `TZ=:Europe/Amsterdam`.

`--language=`LANG

  Takes a specifier indicating the preferred language of the user. The `$LANG` environment variable is initialized from this value on login, and thus a value suitable for this environment variable is accepted here, for example `--language=de_DE.UTF8`

`--ssh-authorized-keys=`KEYS

  Either takes a SSH authorized key line to associate with the user record or a `@` character followed by a path to a file to read one or more such lines from. SSH keys configured this way are made available to SSH to permit access to this home directory and user record. This option may be used more than once to configure multiple SSH keys.

`--pkcs11-token-uri=`URI

  Takes an RFC 7512 PKCS#11 URI referencing a security token (e.g. YubiKey or PIV smartcard) that shall be able to unlock the user account. The security token URI should reference a security token with exactly one pair of X.509 certificate and private key. A random secret key is then generated, encrypted with the public key of the X.509 certificate, and stored as part of the user record. At login time it is decrypted with the PKCS#11 module and then used to unlock the account and associated resources. See below for an example how to set up authentication with security token.

`--locked=`BOOLEAN

  Takes a boolean argument. Specifies whether this user account shall be locked. If true logins into this account are prohibited, if false (the default) they are permitted (of course, only if authorization otherwise succeeds).

`--not-before=`TIMESTAMP
`--not-after=`TIMESTAMP

  These options take a timestamp string, in the format documented in systemd.time 7 and configures points in time before and after logins into this account are not permitted.

`--rate-limit-interval=`SECS
`--rate-limit-burst=`NUMBER

  Configures a rate limit on authentication attempts for this user. If the user attempts to authenticate more often than the specified number, on a specific system, within the specified time interval authentication is refused until the time interval passes. Defaults to 10 times per 1min.

`--password-hint=`TEXT

  Takes a password hint to store alongside the user record. This string is stored accessible only to privileged users and the user itself and may not be queried by other users. Example: `--password-hint="My first pet's name"`

`--enforce-password-policy=`BOOL
`-P`

  Takes a boolean argument. Configures whether to enforce the system's password policy for this user, regarding quality and strength of selected passwords. Defaults to on. `-P` is short for `---enforce-password-policy=no`.

`--password-change-now=`BOOL

  Takes a boolean argument. If true the user is asked to change their password on next login.

`--password-change-min=`TIME
`--password-change-max=`TIME
`--password-change-warn=`TIME
`--password-change-inactive=`TIME

  Each of these options takes a time span specification as argument (in the syntax documented in systemd.time 5) and configure various aspects of the user's password expiration policy. Specifically, `--password-change-min=` configures how much time has to pass after changing the password of the user until the password may be changed again. If the user tries to change their password before this time passes the attempt is refused. `--password-change-max=` configures how much time has to pass after the the password is changed until the password expires and needs to be changed again. After this time passes any attempts to log in may only proceed after the password is changed. `--password-change-warn=` specifies how much earlier than then the time configured with `--password-change-max=` the user is warned at login to change their password as it will expire soon. Finally `--password-change-inactive=` configures the time which has to pass after the password as expired until the user is not permitted to log in or change the password anymore. Note that these options only apply to password authentication, and do not apply to other forms of authentication, for example PKCS#11-based security token authentication.

`--disk-size=`BYTES

  Either takes a size in bytes as argument (possibly using the usual K, M, G, … suffixes for 1024 base values), or a percentage value and configures the disk space to assign to the user. If a percentage value is specified (i.e. the argument suffixed with `%`) it is taken relative to the available disk space of the backing file system. If the LUKS2 backend is used this configures the size of the loopback file and file system contained therein. For the other storage backends configures disk quota using the filesystem's native quota logic, if available. If not specified, defaults to 85% of the available disk space for the LUKS2 backend and to no quota for the others.

`--access-mode=`MODE

  Takes a UNIX file access mode written in octal. Configures the access mode of the home directory itself. Note that this is only used when the directory is first created, and the user may change this any time afterwards. Example: `--access-mode=0700`

`--umask=`MASK

  Takes the access mode mask (in octal syntax) to apply to newly created files and directories of the user ("umask"). If set this controls the initial umask set for all login sessions of the user, possibly overriding the system's defaults.

`--nice=`NICE

  Takes the numeric scheduling priority ("nice level") to apply to the processes of the user at login time. Takes a numeric value in the range -20 (highest priority) to 19 (lowest priority).

`--rlimit=`LIMIT=VALUE:VALUE

  Allows configuration of resource limits for processes of this user, see getrlimit 2 for details. Takes a resource limit name (e.g. `LIMIT_NOFILE`) followed by an equal sign, followed by a numeric limit. Optionally, separated by colon a second numeric limit may be specified. If two are specified this refers to the soft and hard limits, respectively. If only one limit is specified the setting sets both limits in one.

`--tasks-max=`TASKS

  Takes a non-zero unsigned integer as argument. Configures the maximum numer of tasks (i.e. processes and threads) the user may have at any given time. This limit applies to all tasks forked off the user's sessions, even if they change user identity via su 1 or a similar tool. Use `--rlimit=LIMIT_NPROC=` to place a limit on the tasks actually running under the UID of the user, thus excluding any child processes that might have changed user identity. This controls the `TasksMax=` settting of the per-user systemd slice unit `user-$UID.slice`. See systemd.resource-control 5 for further details.

`--memory-high=`BYTES
`--memory-max=`BYTES

  Set a limit on the memory a user may take up on a system at any given time in bytes (the usual K, M, G, … suffixes are supported, to the base of 1024). This includes all memory used by the user itself and all processes they forked off that changed user credentials. This controls the `MemoryHigh=` and `MemoryMax=` settings of the per-user systemd slice unit `user-$UID.slice`. See systemd.resource-control 5 for further details.

`--cpu-weight=`WEIGHT
`--io-weight=`WEIGHT

  Set a CPU and IO scheduling weights of the processes of the user, including those of processes forked off by the user that changed user credentials. Takes a numeric value in the range 1…10000. This controls the `CPUWeight=` and `IOWeight=` settings of the per-user systemd slice unit `user-$UID.slice`. See systemd.resource-control 5 for further details.

`--storage=`STORAGE

  Selects the storage mechanism to use for this home directory. Takes one of `luks`, `fscrypt`, `directory`, `subvolume`, `cifs`. For details about these mechanisms, see above. If a new home directory is created and the storage type is not specifically specified defaults to `luks` if supported, `subvolume` as first fallback if supported, and `directory` if not.

`--image-path=`PATH

  Takes a file system path. Configures where to place the user's home directory. When LUKS2 storage is used refers to the path to the loopback file, otherwise to the path to the home directory. When unspecified defaults to `/home/$USER.home` when LUKS storage is used and `/home/$USER.homedir` for the other storage mechanisms. Not defined for the `cifs` storage mechanism. To use LUKS2 storage on a regular block device (for example a USB stick) pass the path to the block device here.

`--fs-type=`TYPE

  When LUKS2 storage is used configures the file system type to use inside the home directory LUKS2 container. One of `ext4`, `xfs`, `btrfs`. If not specified defaults to `ext4`. Note that `xfs` is not recommended as its support for file system resizing is too limited.

`--luks-discard=`BOOL

  When LUKS2 storage is used configures whether to enable the `discard` feature of the file system. If enabled the file system on top of the LUKS2 volume will report empty block information to LUKS2 and the loopback file below, ensuring that empty space in the home directory is returned to the backing file system below the LUKS2 volume, resulting in a "sparse" loopback file. This option mostly defaults to off, since this permits over-committing home directories which results in I/O errors if the underlying file system runs full while the upper file system wants to allocate a block. Such I/O errors are generally not handled well by file systems nor applications. When LUKS2 storage is used on top of regular block devices (instead of on top a loopback file) the discard logic defaults to on.

`--luks-cipher=`CIPHER
`--luks-cipher-mode=`MODE
`--luks-volume-key-size=`BITS
`--luks-pbkdf-type=`TYPE
`--luks-pbkdf-hash-algorithm=`ALGORITHM
`--luks-pbkdf-time-cost=`SECONDS
`--luks-pbkdf-memory-cost=`BYTES
`--luks-pbkdf-parallel-threads=`THREADS

  Configures various cryptographic parameters for the LUKS2 storage mechanism. See cryptsetup 8 for details on the specific attributes.

`--nosuid=`BOOL
`--nodev=`BOOL
`--noexec=`BOOL

  Configures the `nosuid`, `nodev` and `noexec` mount options for the home directories. By default `nodev` and `nosuid` are on, while `noexec` is off. For details about these mount options see mount 8.

`--cifs-domain=`DOMAIN
`--cifs-user-name=`USER
`--cifs-service=`SERVICE

  Configures the Windows File Sharing (CIFS) domain and user to associate with the home directory/user account, as well as the file share ("service") to mount as directory. The latter is used when `cifs` storage is selected.

`--stop-delay=`SECS

  Configures the time the per-user service manager shall continue to run after the all sessions of the user ended. The default is configured in logind.conf 5 (for home directories of LUKS2 storage located on removable media this defaults to 0 though). A longer time makes sure quick, repetitive logins are more efficient as the user's service manager doesn't have to be started every time.

`--kill-processes=`BOOL

  Configures whether to kill all processes of the user on logout. The default is configured in logind.conf 5.

`--auto-login=`BOOL

  Takes a boolean argument. Configures whether the graphical UI of the system should automatically log this user in if possible. Defaults to off. If less or more than one user is marked this way automatic login is disabled.

## Commands

The following commands are understood:

`list`

  List all home directories (along with brief details) currently managed by `systemd-homed.service`. This command is also executed if none is specified on the command line. (Note that the list of users shown by this command does not include users managed by other subsystems, such as system users or any traditional users listed in `/etc/passwd`.)

`activate` USER [USER…]

  Activate one or more home directories. The home directories of each listed user will be activated and made available under their mount points (typically in `/home/$USER`). Note that any home activated this way stays active indefinitely, until it is explicitly deactivated again (with `deactivate`, see below), or the user logs in and out again and it thus is deactivated due to the automatic deactivation-on-logout logic.

  Activation of a home directory involves various operations that depend on the selected storage mechanism. If the LUKS2 mechanism is used, this generally involves: inquiring the user for a password, setting up a loopback device, validating and activating the LUKS2 volume, checking the file system, mounting the file system, and potentiatlly changing the ownership of all included files to the correct UID/GID.

`deactivate` USER [USER…]

  Deactivate one or more home directories. This undoes the effect of `activate`.

`inspect` USER [USER…]

  Show various details about the specified home directories. This shows various information about the home directory and its user account, including runtime data such as current state, disk use and similar. Combine with `--json=` to show the detailed JSON user record instead, possibly combined with `--export-format=` to suppress certain aspects of the output.

`authenticate` USER [USER…]

  Validate authentication credentials of a home directory. This queries the caller for a password (or similar) and checks that it correctly unlocks the home directory. This leaves the home directory in the state it is in, i.e. it leaves the home directory in inactive state if it was inactive before, and in active state if it was active before.

`create` USER
`create` `--identity=`PATH USER

  Create a new home directory/user account of the specified name. Use the various user record property options (as documented above) to control various aspects of the home directory and its user accounts.

`remove` USER

  Remove a home directory/user account. This will remove both the home directory's user record and the home directory itself, and thus delete all files and directories owned by the user.

`update` USER
`update` `--identity=`PATH USER

  Update a home directory/user account. Use the various user record property options (as documented above) to make changes to the account, or alternatively provide a full, updated JSON user record via the `--identity=` option.

  Note that changes to user records not signed by a cryptographic private key available locally are not permitted, unless `--identity=` is used with a user record that is already correctly signed by a recognized private key.

`passwd` USER

  Change the password of the specified home direcory/user account.

`resize` USER BYTES

  Change the disk space assigned to the specified home directory. If the LUKS2 storage mechanism is used this will automatically resize the loopback file and the file system contained within. Note that if `ext4` is used inside of the LUKS2 volume, it is necessary to deactivate the home directory before shrinking it (i.e the user has to log out). Growing can be done while the home directory is active. If `xfs` is used inside of the LUKS2 volume the home directory may not be shrunk whatsoever. On all three of `ext4`, `xfs` and `btrfs` the home directory may be grown while the user is logged in, and on the latter also shrunk while the user is logged in. If the `subvolume`, `directory`, `fscrypt` storage mechanisms are used, resizing will change file system quota.

`lock` USER

  Temporarily suspend access to the user's home directory and remove any associated cryptographic keys from memory. Any attempts to access the user's home directory will stall until the home directory is unlocked again (i.e. re-authenticated). This functionality is primarily intended to be used during system suspend to make sure the user's data cannot be accessed until the user re-authenticates on resume. This operation is only defined for home directories that use the LUKS2 storage mechanism.

`unlock` USER

  Resume access to the user's home directory again, undoing the effect of `lock` above. This requires authentication of the user, as the cryptographic keys required for access to the home directory need to be reacquired.

`lock-all`

  Execute the `lock` command on all suitable home directories at once. This operation is generally executed on system suspend (i.e. by `systemctl suspend` and related commands), to ensure all active user's cryptographic keys for accessing their home directories are removed from memory.

`with` USER COMMAND…

  Activate the specified user's home directory, run the specified command (under the caller's identity, not the specified user's) and deactivate the home directory afterwards again (unless the user is logged in otherwise). This command is useful for running privileged backup scripts and such, but requires authentication with the user's credentials in order to be able to unlock the user's home directory.

## Exit status

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

## Examples

Create a user `waldo` in the administrator group `wheel`, and assign 500 MiB disk space to them.

    homectl create waldo --real-name="Waldo McWaldo" -G wheel --disk-size=500M

Create a user `wally` on a USB stick, and assign a maximum of 500 concurrent tasks to them.

    homectl create wally --real-name="Wally McWally" --image-path=/dev/disk/by-id/usb-SanDisk_Ultra_Fit_476fff954b2b5c44-0:0 --tasks-max=500

Change nice level of user `odlaw` to +5 and make sure the environment variable `$SOME` is set to the string `THING` for them on login.

    homectl update odlaw --nice=5 --setenv=SOME=THING

Set up authentication with a YubiKey security token:

    # Clear the Yubikey from any old keys (careful!)
    ykman piv reset

    # Generate a new private/public key pair on the device, store the public key in 'pubkey.pem'.
    ykman piv generate-key -a RSA2048 9d pubkey.pem

    # Create a self-signed certificate from this public key, and store it on the device.
    ykman piv generate-certificate --subject "Knobelei" 9d pubkey.pem

    # We don't need the publibc key on disk anymore
    rm pubkey.pem

    # Check if the newly create key on the Yubikey shows up as token in PKCS#11. Have a look at the output, and
    # copy the resulting token URI to the clipboard.
    p11tool --list-tokens

    # Allow the security token referenced by the determined PKCS#11 URI to unlock the account of user
    # 'lafcadio'. (Replace the '…' by the URI from the clipboard.)
    homectl update lafcadio --pkcs11-token-uri=…

## See Also

systemd 1, systemd-homed.service 8, userdbctl 1, useradd 8, cryptsetup 8