pam_systemd

PAM_SYSTEMD(8)                    pam_systemd                   PAM_SYSTEMD(8)

NAME
       pam_systemd - Register user sessions in the systemd login manager

SYNOPSIS
       pam_systemd.so

DESCRIPTION
       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 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 pam_loginuid.so 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 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
       The following options are understood:

       class=
           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.

       type=
           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.

       desktop=
           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.

       debug[=]
           Takes an optional boolean argument. If yes or without the argument,
           the module will log debugging information as it operates.

MODULE TYPES PROVIDED
       Only session is provided.

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

       $XDG_SESSION_ID
           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 for the
           current session.

       $XDG_RUNTIME_DIR
           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.

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

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

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

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

       $XDG_VTNR
           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
       PAM modules earlier in the stack, that is those that come before
       pam_systemd.so, 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.

       systemd.memory_max
           Sets unit MemoryMax=.

       systemd.tasks_max
           Sets unit TasksMax=.

       systemd.cpu_weight
           Sets unit CPUWeight=.

       systemd.io_weight
           Sets unit IOWeight=.

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

           #%PAM-1.0
           auth     sufficient pam_unix.so
           auth     required   pam_deny.so

           account  required   pam_nologin.so
           account  sufficient pam_unix.so
           account  required   pam_permit.so

           password sufficient pam_unix.so sha512 shadow try_first_pass try_authtok
           password required   pam_deny.so

           -session optional   pam_loginuid.so
           -session optional   pam_systemd.so
           session  required   pam_unix.so

SEE ALSO
       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
        1. JSON User Record
           https://systemd.io/USER_RECORD

        2. Desktop Entry Specification
           http://standards.freedesktop.org/desktop-entry-spec/latest/

        3. XDG Base Directory Specification
           http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

systemd 245                                                     PAM_SYSTEMD(8)