NAME¶
pam_elogind - Register user sessions in the elogind login
manager
DESCRIPTION¶
pam_elogind registers user sessions with the
elogind(8) login manager, and hence the elogind 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 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 $XDG_SESSION_ID environment variable is
initialized. If auditing is available and pam_loginuid.so was run
before this module (which is highly recommended), the variable is initialized
from the auditing session id (/proc/self/sessionid). Otherwise, an independent
session counter is used.
3.The "$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 elogind 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 elogind 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.
Added in version 197.
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.
Added in version 209.
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.
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
"elogind-user" service. Otherwise defaults to the empty set.
Added in version 254.
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.
$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.
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.
$XDG_SESSION_TYPE
The session type. This may be used instead of
type= on the module parameter line, and is usually preferred.
Added in version 209.
$XDG_SESSION_CLASS
The session class. This may be used instead of
class= on the module parameter line, and is usually preferred.
Added in version 209.
$XDG_SESSION_DESKTOP
The desktop identifier. This may be used instead of
desktop= on the module parameter line, and is usually preferred.
Added in version 209.
$XDG_SEAT
The seat name the session shall be registered for, if
any.
Added in version 209.
$XDG_VTNR
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_elogind 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_elogind.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.
systemd.memory_max=
Sets unit
MemoryMax=.
Added in version 239.
systemd.tasks_max=
Sets unit
TasksMax=.
Added in version 239.
systemd.runtime_max_sec=
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.runtime_max_sec", (void *)"3600", cleanup);
EXAMPLE¶
Here's an example PAM configuration fragment that allows users
sessions to be managed by
elogind:
#%PAM-1.0
auth required pam_shells.so
auth required pam_nologin.so
auth include system-auth
account required pam_access.so
account required pam_nologin.so
account required pam_time.so
account include system-auth
password include system-auth
session optional pam_loginuid.so
session required pam_env.so envfile=/etc/profile.env
session optional pam_lastlog.so silent
session include system-auth
session optional pam_motd.so motd=/etc/motd
session optional pam_mail.so
-session optional pam_elogind.so
NOTES¶
- 1.
- JSON User Records
- 2.
- Desktop Entry Specification
- 3.
- XDG Base Directory Specification
