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

Provided by: systemd-userdbd_255.4-1ubuntu8.4_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). 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.

$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.

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
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