USERDBCTL(1)

NAME
userdbctl - Inspect users, groups and group memberships

SYNOPSIS

userdbctl [OPTIONS...] {COMMAND} [NAME...]

DESCRIPTION

userdbctl may be used to inspect user and groups (as well as group memberships) of the system. This client utility inquires user/group information provided by various system services, both operating on JSON user/group records (as defined by the JSON User Records[1] and JSON Group Records[2] definitions), and classic UNIX NSS/glibc user and group records. This tool is primarily a client to the User/Group Record Lookup API via Varlink[3], and may also pick up drop-in JSON user and group records from /etc/userdb/, /run/userdb/, /run/host/userdb/, /usr/lib/userdb/ (see nss-systemd(8) for details about drop-in user records).

OPTIONS

The following options are understood:

--output=MODE
    Chooses the output mode. Takes one of "classic", "friendly", "table" or "json". If "classic", an output very close to the format of /etc/passwd or /etc/group is generated. If "friendly", a more comprehensive and user friendly, human-readable output is generated. If "table", a minimal, tabular output is generated. If "json", a JSON formatted output is generated. Defaults to "friendly" if a user/group is specified on the command line, "table" otherwise.

    Note that most output formats do not show all available information. In particular, "classic" and "table" show only the most important fields. Various modes also do not show password hashes. Use "json" to view all fields, including any authentication fields.

    Added in version 245.

--json=FORMAT
    Selects JSON output mode (like --output=json) and selects the precise display mode. Takes one of "pretty" or "short". 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.

    Added in version 250.

--service=SERVICE[:SERVICE...], -s SERVICE:SERVICE...
    Controls which services to query for users/groups. Takes a list of one or more service names, separated by ":". See below for a list of well-known service names. If not specified, all available services are queried at once.

    Added in version 245.

--with-nss=BOOL
    Controls whether to include classic glibc/NSS user/group lookups in the output. If --with-nss=no is used, any attempts to resolve or enumerate users/groups provided only via glibc NSS is suppressed. If --with-nss=yes is specified, such users/groups are included in the output (which is the default).

    Added in version 245.

--with-varlink=BOOL
    Controls whether to include Varlink user/group lookups in the output, i.e. those done via the User/Group Record Lookup API via Varlink[3]. If --with-varlink=no is used, any attempts to resolve or enumerate users/groups provided only via Varlink are suppressed. If --with-varlink=yes is specified, such users/groups are included in the output (which is the default).

    Added in version 249.

--with-dropin=BOOL
    Controls whether to include user/group lookups in the output that are defined using drop-in files in /etc/userdb/, /run/userdb/, /run/host/userdb/, /usr/lib/userdb/. If --with-dropin=no is used, these records are suppressed. If --with-dropin=yes is specified, such users/groups are included in the output (which is the default).

    Added in version 249.

--synthesize=BOOL
    Controls whether to synthesize records for the root and nobody users/groups if they are not defined otherwise, as well as the user/groups for the "foreign" UID range. By default (or with "yes"), such records are implicitly synthesized if otherwise missing since they have special significance to the OS. When "no", this synthesizing is turned off.

    Added in version 245.

-N
    This option is short for --with-nss=no --synthesize=no. Use this option to show only records that are natively defined as JSON user or group records, with all NSS/glibc compatibility and all implicit synthesis turned off.

    Added in version 245.

--multiplexer=BOOL
    Controls whether to do lookups via the multiplexer service (if specified as true, the default) or do lookups in the client (if specified as false). Using the multiplexer service is typically preferable, since it runs in a locked down sandbox.

    Added in version 250.

--chain
    When used with the ssh-authorized-keys command, this will allow passing an additional command line after the user name that is chain executed after the lookup completed. This allows chaining multiple tools that show SSH authorized keys.

    Added in version 250.

--fuzzy, -z
    When used with the user or group command, do a fuzzy string search. Any specified arguments will be matched against the user name, the real name of the user record, the email address, and other descriptive strings of the user or group record. Moreover, instead of precise matching, a substring match or a match allowing slight deviations in spelling is applied.

    Added in version 257.

--disposition=
    When used with the user or group command, filters by disposition of the record. Takes one of "intrinsic", "system", "regular", "dynamic", "container". May be used multiple times, in which case only users matching any of the specified dispositions are shown.

    Added in version 257.

-I, -S, -R
    Shortcuts for --disposition=intrinsic, --disposition=system, --disposition=regular, respectively.

    Added in version 257.

--uid-min=, --uid-max=
    When used with the user or group command, filters the output by UID/GID ranges. Takes numeric minimum or maximum UID/GID values, respectively. Shows only records within the specified range. When applied to the user command, it matches against UIDs. When applied to the group command, matches against GIDs (despite the name of the switch). If unspecified, defaults to 0 (for the minimum) and 4294967294 (for the maximum), i.e. by default, no filtering is applied, as the whole UID/GID range is covered.

    Added in version 257.

--uuid=
    When used with the user or group command, filters the output to the record with the specified UUID. If unspecified, no UUID-based filtering is applied.

    Added in version 259.

--boundaries=
    When used with the user or group command, controls whether to show relevant UID/GID range boundary information in the tabular output. Takes a boolean. Defaults to true.

    Added in version 257.

-B
    Shortcut for --boundaries=no.

    Added in version 257.

--from-file=PATH, -F
    When used with the user or group command, read the user definition in JSON format from the specified file, instead of querying it from the system. If the path is specified as "-", reads the JSON data from standard input. This is useful to validate and introspect JSON user or group records quickly, and check how they would be interpreted on the local system.

    Added in version 258.

--no-pager
    Do not pipe output into a pager.

--no-legend
    Do not print the legend, i.e. column headers and the footer with hints.

-h, --help
    Print a short help text and exit.

--version
    Print a short version string and exit.

COMMANDS

The following commands are understood:

user [USER...]
    List all known users records or show details of one or more specified user records. Use --output= to tweak output mode.

    If used in conjunction with --from-file= the user record data is read in JSON format from the specified file instead of querying it from the system. For details see above.

    Added in version 245.

group [GROUP...]
    List all known group records or show details of one or more specified group records. Use --output= to tweak the output mode.

    If used in conjunction with --from-file= the group record data is read in JSON format from the specified file instead of querying it from the system. For details see above.

    Added in version 245.

users-in-group [GROUP...]
    List users that are members of the specified groups. If no groups are specified, list all user/group memberships defined. Use --output= to tweak the output mode.

    Added in version 245.

groups-of-user [USER...]
    Lists groups that the specified users are members of. If no users are specified, lists all user/group memberships defined (in this case, groups-of-user and users-in-group are equivalent). Use --output= to tweak the output mode.

    Added in version 245.

services
    List all services currently providing user/group definitions to the system. See below for a list of well-known services providing user information.

    Added in version 245.

ssh-authorized-keys
    Show SSH authorized keys for this account. This command is intended to be used to allow the SSH daemon to pick up authorized keys from user records, see below.

    Added in version 245.

load-credentials
    When specified, the following credentials are used when passed in:

    userdb.user.*, userdb.group.*
        These credentials should contain valid JSON User[1] and JSON Group[2] records. For each matching credential, various files are created in /etc/userdb/, implementing the interface described in nss-systemd(8). Any passed user records must contain valid UID and GID fields. Any passed group records must contain a GID field (i.e. automatic UID/GID allocation is not supported). For both user and group records, the credential suffix (for "userdb.user.foobar" the suffix is "foobar") must match the user or group name encoded in the record.

        Added in version 258.

    Added in version 258.

WELL-KNOWN SERVICES

The userdbctl services command will list all currently running services that provide user or group definitions to the system. The following well-known services are shown among this list:

io.systemd.DynamicUser
    This service is provided by the system service manager itself (i.e. PID 1) and makes all users (and their groups) synthesized through the DynamicUser= setting in service unit files available to the system (see systemd.exec(5) for details about this setting).

    Added in version 245.

io.systemd.Home
    This service is provided by systemd-homed.service(8) and makes all users (and their groups) belonging to home directories managed by that service available to the system.

    Added in version 245.

io.systemd.Machine
    This service is provided by systemd-machined.service(8) and synthesizes records for all users/groups used by a container that employs user namespacing.

    Added in version 246.

io.systemd.Multiplexer
    This service is provided by systemd-userdbd.service(8) and multiplexes user/group look-ups to all other running lookup services. This is the primary entry point for user/group record clients, as it simplifies client side implementation substantially, since they can ask a single service for lookups instead of asking all running services in parallel. userdbctl uses this service preferably, too, unless --with-nss= or --service= are used, in which case finer control over the services to talk to is required.

    Added in version 245.

io.systemd.NameServiceSwitch
    This service is (also) provided by systemd-userdbd.service(8) and converts classic NSS/glibc user and group records to JSON user/group records, providing full backwards compatibility. Use --with-nss=no to disable this compatibility, see above. Note that compatibility is actually provided in both directions: nss-systemd(8) will automatically synthesize classic NSS/glibc user/group records from all JSON user/group records provided to the system, thus using both APIs is mostly equivalent and provides access to the same data, however the NSS/glibc APIs necessarily expose a more reduced set of fields only.

    Added in version 245.

io.systemd.DropIn
    This service is (also) provided by systemd-userdbd.service(8) and picks up JSON user/group records from /etc/userdb/, /run/userdb/, /run/host/userdb/, /usr/lib/userdb/.

    Added in version 249.

Note that userdbctl has internal support for NSS-based lookups too. This means that if neither io.systemd.Multiplexer nor io.systemd.NameServiceSwitch are running, look-ups into the basic user/group databases will still work.

INTEGRATION WITH SSH

The userdbctl tool may be used to make the list of SSH authorized keys possibly contained in a user record available to the SSH daemon for authentication. For that, configure the following in sshd_config(5):

    ...
    AuthorizedKeysCommand /usr/bin/userdbctl ssh-authorized-keys %u
    AuthorizedKeysCommandUser root
    ...

Sometimes, it is useful to allow chain invocation of another program to list SSH authorized keys. By using the --chain option, such a tool may be chain executed by userdbctl ssh-authorized-keys once a lookup completes, regardless of whether an SSH key was found or not. Example:

    ...
    AuthorizedKeysCommand /usr/bin/userdbctl ssh-authorized-keys %u --chain /usr/bin/othertool %u
    AuthorizedKeysCommandUser root
    ...

The above will first query the userdb database for SSH keys, and then chain execute /usr/bin/othertool to also be queried.

EXIT STATUS

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

ENVIRONMENT

$SYSTEMD_LOG_LEVEL
    The maximum log level of emitted messages (messages with a higher log level, i.e. less important ones, will be suppressed). Takes a comma-separated list of values. A value may be either one of (in order of decreasing importance) emerg, alert, crit, err, warning, notice, info, debug, or an integer in the range 0...7. See syslog(3) for more information. Each value may optionally be prefixed with one of console, syslog, kmsg or journal followed by a colon to set the maximum log level for that specific log target (e.g. SYSTEMD_LOG_LEVEL=debug,console:info specifies to log at debug level except when logging to the console which should be at info level). Note that the global maximum log level takes priority over any per target maximum log levels.

$SYSTEMD_LOG_COLOR
    A boolean. If true, messages written to the tty will be colored according to priority.

    This setting is only useful when messages are written directly to the terminal, because journalctl(1) and other tools that display logs will color messages based on the log level on their own.

$SYSTEMD_LOG_TIME
    A boolean. If true, console log messages will be prefixed with a timestamp.

    This setting is only useful when messages are written directly to the terminal or a file, because journalctl(1) and other tools that display logs will attach timestamps based on the entry metadata on their own.

$SYSTEMD_LOG_LOCATION
    A boolean. If true, messages will be prefixed with a filename and line number in the source code where the message originates.

    Note that the log location is often attached as metadata to journal entries anyway. Including it directly in the message text can nevertheless be convenient when debugging programs.

$SYSTEMD_LOG_TID
    A boolean. If true, messages will be prefixed with the current numerical thread ID (TID).

    Note that the this information is attached as metadata to journal entries anyway. Including it directly in the message text can nevertheless be convenient when debugging programs.

$SYSTEMD_LOG_TARGET
    The destination for log messages. One of console (log to the attached tty), console-prefixed (log to the attached tty but with prefixes encoding the log level and "facility", see syslog(3), kmsg (log to the kernel circular log buffer), journal (log to the journal), journal-or-kmsg (log to the journal if available, and to kmsg otherwise), auto (determine the appropriate log target automatically, the default), null (disable log output).

$SYSTEMD_LOG_RATELIMIT_KMSG
    Whether to ratelimit kmsg or not. Takes a boolean. Defaults to "true". If disabled, systemd will not ratelimit messages written to kmsg.

$SYSTEMD_PAGER, $PAGER
    Pager to use when --no-pager is not given. $SYSTEMD_PAGER is used if set; otherwise $PAGER is used. If neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known pager implementations is tried in turn, including less(1) and more(1), until one is found. If no pager implementation is discovered, no pager is invoked. Setting those environment variables to an empty string or the value "cat" is equivalent to passing --no-pager.

    Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER and $PAGER can only be used to disable the pager (with "cat" or ""), and are otherwise ignored.

$SYSTEMD_LESS
    Override the options passed to less (by default "FRSXMK").

    Users might want to change two options in particular:

    K
        This option instructs the pager to exit immediately when Ctrl+C is pressed. To allow less to handle Ctrl+C itself to switch back to the pager command prompt, unset this option.

        If the value of $SYSTEMD_LESS does not include "K", and the pager that is invoked is less, Ctrl+C will be ignored by the executable, and needs to be handled by the pager.

    X
        This option instructs the pager to not send termcap initialization and deinitialization strings to the terminal. It is set by default to allow command output to remain visible in the terminal even after the pager exits. Nevertheless, this prevents some pager functionality from working, in particular paged output cannot be scrolled with the mouse.

    Note that setting the regular $LESS environment variable has no effect for less invocations by systemd tools.

    See less(1) for more discussion.

$SYSTEMD_LESSCHARSET
    Override the charset passed to less (by default "utf-8", if the invoking terminal is determined to be UTF-8 compatible).

    Note that setting the regular $LESSCHARSET environment variable has no effect for less invocations by systemd tools.

$SYSTEMD_PAGERSECURE
    Common pager commands like less(1), in addition to "paging", i.e. scrolling through the output, support opening of or writing to other files and running arbitrary shell commands. When commands are invoked with elevated privileges, for example under sudo(8) or pkexec(1), the pager becomes a security boundary. Care must be taken that only programs with strictly limited functionality are used as pagers, and unintended interactive features like opening or creation of new files or starting of subprocesses are not allowed. "Secure mode" for the pager may be enabled as described below, if the pager supports that (most pagers are not written in a way that takes this into consideration). It is recommended to either explicitly enable "secure mode" or to completely disable the pager using --no-pager or PAGER=cat when allowing untrusted users to execute commands with elevated privileges.

    This option takes a boolean argument. When set to true, the "secure mode" of the pager is enabled. In "secure mode", LESSSECURE=1 will be set when invoking the pager, which instructs the pager to disable commands that open or create new files or start new subprocesses. Currently only less(1) is known to understand this variable and implement "secure mode".

    When set to false, no limitation is placed on the pager. Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited environment may allow the user to invoke arbitrary commands.

    When $SYSTEMD_PAGERSECURE is not set, systemd tools attempt to automatically figure out if "secure mode" should be enabled and whether the pager supports it. "Secure mode" is enabled if the effective UID is not the same as the owner of the login session, see geteuid(2) and sd_pid_get_owner_uid(3), or when running under sudo(8) or similar tools ($SUDO_UID is set [4]). In those cases, SYSTEMD_PAGERSECURE=1 will be set and pagers which are not known to implement "secure mode" will not be used at all. Note that this autodetection only covers the most common mechanisms to elevate privileges and is intended as convenience. It is recommended to explicitly set $SYSTEMD_PAGERSECURE or disable the pager.

    Note that if the $SYSTEMD_PAGER or $PAGER variables are to be honoured, other than to disable the pager, $SYSTEMD_PAGERSECURE must be set too.

$SYSTEMD_COLORS
    Takes a boolean argument, or a special value. By default (unset), systemd and related utilities will use colors in their output if possible. If $COLORTERM is set to "truecolor" or "24bit", 24-bit colors will be enabled, 256 colors otherwise, unless $NO_COLOR or $TERM indicates colors are disabled.

    true
        Same as unset, except that $NO_COLOR is ignored.

    false
        The output will be monochrome.

    "16", "256", "24bit"
        Always use the base 16 ANSI colors, 256 colors, or 24 bit color, respectively.

    "auto-16", "auto-256", "auto-24bit"
        Use the given quantity of colours, subject to $TERM, and what the console is connected to.

$SYSTEMD_URLIFY
    The value must be a boolean. Controls whether clickable links should be generated in the output for terminal emulators supporting this. This can be specified to override the decision that systemd makes based on $TERM and other conditions.

SEE ALSO

systemd(1), systemd-userdbd.service(8), systemd-homed.service(8), nss-systemd(8), getent(1)

NOTES

1.  JSON User Records
    https://systemd.io/USER_RECORD

2.  JSON Group Records
    https://systemd.io/GROUP_RECORD

3.  User/Group Record Lookup API via Varlink
    https://systemd.io/USER_GROUP_API

4.  It is recommended for other tools to set and check $SUDO_UID as appropriate, treating it is a common interface.