NAME
pam_systemd - Register user sessions in the systemd control group
hierarchy
SYNOPSIS
pam_systemd.so
DESCRIPTION
pam_systemd registers user sessions in the systemd control group
hierarchy.
On login, this module ensures the following:
1. If it does not exist yet, the user runtime directory
/run/user/$USER is created and its ownership changed to the user
that is logging in.
2. If create-session=1 is set, the $XDG_SESSION_ID environment
variable is initialized. If auditing is available and
pam_loginuid.so run before this module (which is highly
recommended), the variable is initialized from the auditing session
id (/proc/self/sessionid). Otherwise an independent session counter
is used.
3. If create-session=1 is set, a new control group
/user/$USER/$XDG_SESSION_ID is created and the login process moved
into it.
4. If create-session=0 is set, a new control group /user/$USER/user is
created and the login process moved into it.
On logout, this module ensures the following:
1. If $XDG_SESSION_ID is set and kill-session=1 specified, all
remaining processes in the /user/$USER/$XDG_SESSION_ID control
group are killed and the control group is removed.
2. If $XDG_SESSION_ID is set and kill-session=0 specified, all
remaining processes in the /user/$USER/$XDG_SESSION_ID control
group are migrated to /user/$USER/user and the original control
group is removed.
3. If kill-user=1 is specified, and no other user session control
group remains, except /user/$USER/user, all remaining processes in
the /user/$USER hierarchy are killed and the control group is
removed.
4. If kill-user=0 is specified, and no process remains in the
/user/$USER hierarchy the control group is removed.
5. If the /user/$USER control group was removed the $XDG_RUNTIME_DIR
directory 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:
create-session=
Takes a boolean argument. If true, a new session is created: the
$XDG_SESSION_ID environment variable is set and the login process
moved to the /user/$USER/$XDG_SESSION_ID control group. It is
recommended that all services which are directly created on the
user's behalf set this option. Only for services that shall
automatically be terminated when the user logs out completely,
otherwise create-session=0 should be set.
kill-session=
Takes a boolean argument. If true, all processes created by the
user during his session and from his session will be terminated
when he logs out from his session.
kill-user=
Takes a boolean argument. If true, all processes created by the
user during his session and from his session will be terminated
after he logged out completely. This is a weaker version of
kill-session=1 and is more friendly for users logged in more than
once, as their processes are terminated only on their complete
logout.
kill-only-users=
Takes a comma separated list of user names or numeric user ids as
argument. If this option is used the effect of the kill-session=
and kill-user= options will apply only to the listed users. If this
option is not used the option applies to all local users. Note that
kill-exclude-users= takes precedence over this list and is hence
subtracted from the list specified here.
kill-exclude-users=
Takes a comma separated list of user names or numeric user ids as
argument. Users listed in this argument will not be subject to the
effect of kill-session= or kill-user=. Note that that this option
takes precedence over kill-only-users=, and hence whatever is
listed for kill-exclude-users= is guaranteed to never be killed by
this PAM module, independent of any other configuration setting.
controllers=
Takes a comma separated list of cgroup controllers in which
hierarchies a user/session cgroup will be created by default for
each user logging in, in addition to the cgroup in the named
'name=systemd' hierarchy. If ommited, defaults to an empty list.
This may be used to move user sessions into their own groups in the
'cpu' hierarchy which ensures that every logged in user gets an
equal amount of CPU time regardless how many processes he has
started.
reset-controllers=
Takes a comma separated list of cgroup controllers in which
hierarchies the logged in processes will be reset to the root
cgroup. If ommited, defaults to 'cpu', meaning that a 'cpu' cgroup
grouping inherited from the login manager will be reset for the
processes of the logged in user.
Note that setting kill-user=1 or even kill-session=1 will break tools
like screen(1).
If the options are omitted they default to create-session=1,
kill-session=0, kill-user=0, reset-controllers=cpu, kill-only-users=,
kill-exclude-users=root.
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 file names. 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 his 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 behaviour 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.
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 kill-user=1
SEE ALSO
pam.conf(5), pam.d(5), pam(8), pam_loginuid(8), systemd(1)
AUTHOR
Lennart Poettering <lennart@poettering.net>
Developer