|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMMANDS | WELL-KNOWN SERVICES | INTEGRATION WITH SSH | EXIT STATUS | ENVIRONMENT | SEE ALSO | NOTES | COLOPHON |
|
|
|
USERDBCTL(1) userdbctl USERDBCTL(1)
userdbctl - Inspect users, groups and group memberships
userdbctl [OPTIONS...] {COMMAND} [NAME...]
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/.
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.
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.
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.
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.
On success, 0 is returned, a non-zero failure code otherwise.
$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.
systemd(1), systemd-userdbd.service(8), systemd-homed.service(8),
nss-systemd(8), getent(1)
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
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel USERDBCTL(1)
Pages that refer to this page: homectl(1), systemd.directives(7), systemd.index(7), systemd-homed.service(8), systemd-machined.service(8), systemd-userdbd.service(8)
|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|