pam_systemd(8) — Linux manual page


PAM_SYSTEMD(8)                 pam_systemd                PAM_SYSTEMD(8)

NAME         top

       pam_systemd - Register user sessions in the systemd login manager

SYNOPSIS         top

DESCRIPTION         top

       pam_systemd registers user sessions with the systemd login
       manager systemd-logind.service(8), and hence the systemd control
       group hierarchy.

       The module also applies various resource management and runtime
       parameters to the new session, as configured in the JSON User
       Records[1] of the user, when one is defined.

       On login, this module — in conjunction with
       systemd-logind.service — ensures the following:

        1. If it does not exist yet, the user runtime directory
           /run/user/$UID is either created or mounted as new "tmpfs"
           file system with quota applied, and its ownership changed to
           the user that is logging in.

        2. The $XDG_SESSION_ID environment variable is initialized. If
           auditing is available and was run before this
           module (which is highly recommended), the variable is
           initialized from the auditing session id
           (/proc/self/sessionid). Otherwise, an independent session
           counter is used.

        3. A new systemd scope unit is created for the session. If this
           is the first concurrent session of the user, an implicit
           per-user slice unit below user.slice is automatically created
           and the scope placed into it. An instance of the system
           service user@.service, which runs the systemd user manager
           instance, is started.

        4. The "$TZ", "$EMAIL" and "$LANG" environment variables are
           configured for the user, based on the respective data from
           the user's JSON record (if it is defined). Moreover, any
           environment variables explicitly configured in the user
           record are imported, and the umask, nice level, and resource
           limits initialized.

       On logout, this module ensures the following:

        1. If enabled in logind.conf(5) (KillUserProcesses=), all
           processes of the session are terminated. If the last
           concurrent session of a user ends, the user's systemd
           instance will be terminated too, and so will the user's slice

        2. If the last concurrent session of a user ends, the user
           runtime directory /run/user/$UID and all its contents are
           removed, too.

       If the system was not booted up with systemd as init system, this
       module does nothing and immediately returns PAM_SUCCESS.

OPTIONS         top

       The following options are understood:

           Takes a string argument which sets the session class. The
           XDG_SESSION_CLASS environment variable (see below) takes
           precedence. One of "user", "greeter", "lock-screen" or
           "background". See sd_session_get_class(3) for details about
           the session class.

           Added in version 197.

           Takes a string argument which sets the session type. The
           XDG_SESSION_TYPE environment variable (see below) takes
           precedence. One of "unspecified", "tty", "x11", "wayland" or
           "mir". See sd_session_get_type(3) for details about the
           session type.

           Added in version 209.

           Takes a single, short identifier string for the desktop
           environment. The XDG_SESSION_DESKTOP environment variable
           (see below) takes precedence. This may be used to indicate
           the session desktop used, where this applies and if this
           information is available. For example: "GNOME", or "KDE". It
           is recommended to use the same identifiers and capitalization
           as for $XDG_CURRENT_DESKTOP, as defined by the Desktop Entry
           Specification[2]. (However, note that the option only takes a
           single item, and not a colon-separated list like
           $XDG_CURRENT_DESKTOP.) See sd_session_get_desktop(3) for
           further details.

           Added in version 240.

       default-capability-bounding-set=, default-capability-ambient-set=
           Takes a comma-separated list of process capabilities (e.g.
           CAP_WAKE_ALARM, CAP_BLOCK_SUSPEND, ...) to set for the
           invoked session's processes, if the user record does not
           encode appropriate sets of capabilities directly. See
           capabilities(7) for details on the capabilities concept. If
           not specified, the default bounding set is left as is (i.e.
           usually contains the full set of capabilities). The default
           ambient set is set to CAP_WAKE_ALARM for regular users if the
           PAM session is associated with a local seat or if it is
           invoked for the "systemd-user" service. Otherwise defaults to
           the empty set.

           Added in version 254.

           Takes an optional boolean argument. If yes or without the
           argument, the module will log debugging information as it


       Only session is provided.

ENVIRONMENT         top

       The following environment variables are initialized by the module
       and available to the processes of the user's session:

           A short session identifier, suitable to be used in filenames.
           The string itself should be considered opaque, although often
           it is just the audit session ID as reported by
           /proc/self/sessionid. Each ID will be assigned only once
           during machine uptime. It may hence be used to uniquely label
           files or other resources of this session. Combine this ID
           with the boot identifier, as returned by
           sd_id128_get_boot(3), for a globally unique identifier.

           Path to a user-private user-writable directory that is bound
           to the user login time on the machine. It is automatically
           created the first time a user logs in and removed on the
           user's final logout. If a user logs in twice at the same
           time, both sessions will see the same $XDG_RUNTIME_DIR and
           the same contents. If a user logs in once, then logs out
           again, and logs in again, the directory contents will have
           been lost in between, but applications should not rely on
           this behavior and must be able to deal with stale files. To
           store session-private data in this directory, the user should
           include the value of $XDG_SESSION_ID in the filename. This
           directory shall be used for runtime file system objects such
           as AF_UNIX sockets, FIFOs, PID files and similar. It is
           guaranteed that this directory is local and offers the
           greatest possible file system feature set the operating
           system provides. For further details, see the XDG Base
           Directory Specification[3].  $XDG_RUNTIME_DIR is not set if
           the current user is not the original user of the session.

       $TZ, $EMAIL, $LANG
           If a JSON user record is known for the user logging in these
           variables are initialized from the respective data in the

           Added in version 245.

       The following environment variables are read by the module and
       may be used by the PAM service to pass metadata to the module. If
       these variables are not set when the PAM module is invoked but
       can be determined otherwise they are set by the module, so that
       these variables are initialized for the session and applications
       if known at all.

           The session type. This may be used instead of type= on the
           module parameter line, and is usually preferred.

           Added in version 209.

           The session class. This may be used instead of class= on the
           module parameter line, and is usually preferred.

           Added in version 209.

           The desktop identifier. This may be used instead of desktop=
           on the module parameter line, and is usually preferred.

           Added in version 209.

           The seat name the session shall be registered for, if any.

           Added in version 209.

           The VT number the session shall be registered for, if any.
           (Only applies to seats with a VT available, such as "seat0")

           Added in version 209.

       If not set, pam_systemd will initialize $XDG_SEAT and $XDG_VTNR
       based on the $DISPLAY variable (if the latter is set).

SESSION LIMITS         top

       PAM modules earlier in the stack, that is those that come before, can set session scope limits using the PAM
       context objects. The data for these objects is provided as
       NUL-terminated C strings and maps directly to the respective unit
       resource control directives. Note that these limits apply to
       individual sessions of the user, they do not apply to all user
       processes as a combined whole. In particular, the per-user
       user@.service unit instance, which runs the systemd --user
       manager process and its children, and is tracked outside of any
       session, being shared by all the user's sessions, is not covered
       by these limits.

       See systemd.resource-control(5) for more information about the
       resources. Also, see pam_set_data(3) for additional information
       about how to set the context objects.

           Sets unit MemoryMax=.

           Added in version 239.

           Sets unit TasksMax=.

           Added in version 239.

           Sets unit CPUWeight=.

           Added in version 239.

           Sets unit IOWeight=.

           Added in version 239.

           Sets unit RuntimeMaxSec=.

           Added in version 244.

       Example data as can be provided from an another PAM module:

           pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
           pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
           pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
           pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
           pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);

EXAMPLE         top

       Here's an example PAM configuration fragment that allows users
       sessions to be managed by systemd-logind.service:

           auth      sufficient
           -auth     sufficient
           auth      required

           account   required
           -account  sufficient
           account   sufficient
           account   required

           -password sufficient
           password  sufficient sha512 shadow try_first_pass use_authtok

           password  required

           -session  optional revoke
           -session  optional
           -session  optional
           -session  optional
           session   required

SEE ALSO         top

       systemd(1), systemd-logind.service(8), logind.conf(5),
       loginctl(1), pam_systemd_home(8), pam.conf(5), pam.d(5), pam(8),
       pam_loginuid(8), systemd.scope(5), systemd.slice(5),

NOTES         top

        1. JSON User Records

        2. Desktop Entry Specification

        3. XDG Base Directory Specification

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  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

systemd 255                                               PAM_SYSTEMD(8)

Pages that refer to this page: org.freedesktop.login1(5)systemd.exec(5)user@.service(5)systemd.directives(7)systemd.index(7)pam_systemd_home(8)systemd-logind.service(8)