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

       The module also applies various resource management and runtime
       parameters to the new session, as configured in the JSON User
       Record[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

        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 unit.

        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.

           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

           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

           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 record.

       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.

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

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

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

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

       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=.

           Sets unit TasksMax=.

           Sets unit CPUWeight=.

           Sets unit IOWeight=.

           Sets unit RuntimeMaxSec=.

       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 try_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), systemd.service(5)

NOTES         top

        1. JSON User Record

        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 2020-11-01.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-11-01.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
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       provements to the information in this COLOPHON (which is not part of
       the original manual page), send a mail to

systemd 247                                                   PAM_SYSTEMD(8)

Pages that refer to this page: org.freedesktop.login1(5)systemd.exec(5)systemd-user-runtime-dir(5)user-runtime-dir.service(5)user-runtime-dir@.service(5)user.service(5)user@.service(5)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)pam_systemd_home(8)systemd-logind(8)systemd-logind.service(8)