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 Record[1] and JSON Group Record[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].

OPTIONS

The following options are understood:

--output=MODE
    Choose the output mode, takes one of "classic", "friendly", "table", "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.

--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.

--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).

--synthesize=BOOL
    Controls whether to synthesize records for the root and nobody users/groups if they aren't defined otherwise. By default (or "yes") such records are implicitly synthesized if otherwise missing since they have special significance to the OS. When "no" this synthesizing is turned off.

-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.

--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.

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

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 output mode.

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

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

ssh-authorized-keys
    This operation is not a public, user-facing interface. It is used to allow the SSH daemon to pick up authorized keys from user records, see below.

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).

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.

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.

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.

io.systemd.NameSeviceSwitch
    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.

Note that userdbctl has internal support for NSS-based lookups too. This means that if neither io.systemd.Multiplexer nor io.systemd.NameSeviceSwitch 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
    ...

EXIT STATUS

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

ENVIRONMENT

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

$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.

    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).

$SYSTEMD_PAGERSECURE
    Takes a boolean argument. When true, the "secure" mode of the pager is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set at all, 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). In secure mode, LESSSECURE=1 will be set when invoking the pager, and the pager shall disable commands that open or create new files or start new subprocesses. When $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known to implement secure mode will not be used. (Currently only less(1) implements secure mode.)

    Note: when commands are invoked with elevated privileges, for example under sudo(8) or pkexec(1), care must be taken to ensure that unintended interactive features are not enabled. "Secure" mode for the pager may be enabled automatically as describe above. Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited environment allows the user to invoke arbitrary commands. Note that if the $SYSTEMD_PAGER or $PAGER variables are to be honoured, $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to completely disable the pager using --no-pager instead.

$SYSTEMD_COLORS
    The value must be a boolean. Controls whether colorized output should be generated. This can be specified to override the decision that systemd makes based on $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 Record
    https://systemd.io/USER_RECORD

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

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