Ubuntu Manpage: pam_systemd - Register user sessions in the systemd login manager

Provided by: libpam-systemd_237-3ubuntu10.57_amd64

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.

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.

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 environmental variable
           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 environmental variable
           takes precedence. One of "unspecified", "tty", "x11", "wayland" or "mir". See sd_session_get_type(3)
           for details about the session type.

       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 set for the processes of the user's session:

$XDG_SESSION_ID
A 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.

$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[1]. $XDG_RUNTIME_DIR is not set if the current
user is not the original user of the session.

The following environment variables are read by the module and may be used by the PAM service to pass
metadata to the module:

$XDG_SESSION_TYPE
The session type. This may be used instead of session= 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
A single, short identifier string for the desktop environment. 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
$XDG_SESSION_DESKTOP only takes a single item, and not a colon-separated list like
$XDG_CURRENT_DESKTOP.) See sd_session_get_desktop(3) for more details.

$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")

EXAMPLE

           #%PAM-1.0
           auth       required     pam_unix.so
           auth       required     pam_nologin.so
           account    required     pam_unix.so
           password   required     pam_unix.so
           session    required     pam_unix.so
           session    required     pam_loginuid.so
           session    required     pam_systemd.so

NOTES

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

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