Ubuntu Manpage: userdbctl - Inspect users, groups and group memberships

Provided by: systemd-userdbd_256.5-2ubuntu3.1_amd64

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/.

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.

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 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.

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.

--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.

           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 output mode.

           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 output mode.

           Added in version 245.

       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.

           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.

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's useful to allow chain invocation of another program to list SSH authorized keys. By using
       the --chain such a tool may be chain executed by userdbctl ssh-authorized-keys once a lookup completes
       (regardless if 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, 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 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.

Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well as $PAGER) will be silently
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
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
Takes a boolean argument. When true, systemd and related utilities will use colors in their output,
otherwise the output will be monochrome. Additionally, the variable can take one of the following
special values: "16", "256" to restrict the use of colors to the base 16 or 256 ANSI colors,
respectively. This can be specified to override the automatic decision 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.

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

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

COMMANDS

WELL-KNOWN SERVICES

INTEGRATION WITH SSH

EXIT STATUS

ENVIRONMENT

SEE ALSO

NOTES