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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | MODULE TYPES PROVIDED | ENVIRONMENT | SESSION LIMITS | EXAMPLE | SEE ALSO | NOTES | COLOPHON |
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PAM_SYSTEMD(8) pam_systemd PAM_SYSTEMD(8)
pam_systemd - Register user sessions in the systemd login manager
pam_systemd.so
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
Records[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.
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. See sd_session_get_class(3) for a way to query the
class of a session. The following session classes are defined:
Table 1. Session Classes
┌──────────────────┬───────────────────────────────────┐
│ Name │ Explanation │
├──────────────────┼───────────────────────────────────┤
│ user │ A regular interactive │
│ │ user session. This is │
│ │ the default class for │
│ │ sessions for which a TTY │
│ │ or X display is known at │
│ │ session registration │
│ │ time. │
├──────────────────┼───────────────────────────────────┤
│ user-early │ Similar to "user" but │
│ │ sessions of this class │
│ │ are not ordered after │
│ │ systemd-user-sessions.service(8), │
│ │ i.e. may be started │
│ │ before regular sessions │
│ │ are allowed to be │
│ │ established. This │
│ │ session class is the │
│ │ default for sessions of │
│ │ the root user that would │
│ │ otherwise qualify for │
│ │ the user class, see │
│ │ above. (Added in v256.) │
├──────────────────┼───────────────────────────────────┤
│ user-light │ Similar to user, but sessions of │
│ │ this class will not pull in the │
│ │ user@.service(5) of the user, and │
│ │ thus possibly have no service │
│ │ manager of the user running. │
│ │ (Added in v258.) │
├──────────────────┼───────────────────────────────────┤
│ user-early-light │ Similar to user-early, but │
│ │ sessions of this class will not │
│ │ pull in the user@.service(5) of │
│ │ the user, and thus possibly have │
│ │ no service manager of the user │
│ │ running. (Added in v258.) │
├──────────────────┼───────────────────────────────────┤
│ user-incomplete │ Similar to "user" but for │
│ │ sessions which are not fully set │
│ │ up yet, i.e. have no home │
│ │ directory mounted or similar. │
│ │ This is used by │
│ │ systemd-homed.service(8) to allow │
│ │ users to log in via ssh(1) before │
│ │ their home directory is mounted, │
│ │ delaying the mount until the user │
│ │ provided the unlock password. │
│ │ Sessions of this class are │
│ │ upgraded to the regular user │
│ │ class once the home directory is │
│ │ activated. │
├──────────────────┼───────────────────────────────────┤
│ greeter │ Similar to "user" but for │
│ │ sessions that are spawned by a │
│ │ display manager ephemerally and │
│ │ which prompt the user for login │
│ │ credentials. │
├──────────────────┼───────────────────────────────────┤
│ lock-screen │ Similar to "user" but for │
│ │ sessions that are spawned by a │
│ │ display manager ephemerally and │
│ │ which show a lock screen that can │
│ │ be used to unlock locked user │
│ │ accounts or sessions. │
├──────────────────┼───────────────────────────────────┤
│ background │ Used for background sessions, │
│ │ such as those invoked by cron(8) │
│ │ and similar tools. This is the │
│ │ default class for sessions for │
│ │ which no TTY or X display is │
│ │ known at session registration │
│ │ time. │
├──────────────────┼───────────────────────────────────┤
│ background-light │ Similar to background, but │
│ │ sessions of this class will not │
│ │ pull in the user@.service(5) of │
│ │ the user, and thus possibly have │
│ │ no service manager of the user │
│ │ running. (Added in v256.) │
├──────────────────┼───────────────────────────────────┤
│ manager │ The user@.service(5) service of │
│ │ the user is registered under this │
│ │ session class. (Added in v256.) │
├──────────────────┼───────────────────────────────────┤
│ manager-early │ Similar to manager, but for the │
│ │ root user. Compare with the user │
│ │ vs. user-early situation. (Added │
│ │ in v256.) │
├──────────────────┼───────────────────────────────────┤
│ none │ Skips registering this session │
│ │ with logind. No session scope │
│ │ will be created, and the user │
│ │ service manager will not be │
│ │ started. (Added in v258.) │
└──────────────────┴───────────────────────────────────┘
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",
"mir", or "web". 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
"systemd-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.
Only session is provided.
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.
$SHELL_PROMPT_PREFIX, $SHELL_PROMPT_SUFFIX, $SHELL_WELCOME
These environment variables are initialized from the service
credentials "shell.prompt.prefix", "shell.prompt.suffix" and
"shell.welcome" if set. They are passed to the invoked session
processes, where they are imported into any shell prompt
(specifically $SHELL_PROMPT_PREFIX is added as prefix to $PS1,
and $SHELL_PROMPT_SUFFIX as suffix) or printed on screen when
a shell first initializes.
Added in version 257.
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_systemd will initialize $XDG_SEAT and $XDG_VTNR
based on the $DISPLAY variable (if the latter is set).
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=.
Added in version 239.
systemd.tasks_max=
Sets unit TasksMax=.
Added in version 239.
systemd.cpu_weight=
Sets unit CPUWeight=.
Added in version 239.
systemd.io_weight=
Sets unit IOWeight=.
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.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);
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 sufficient pam_systemd_home.so
auth required pam_deny.so
account required pam_nologin.so
-account sufficient pam_systemd_home.so
account sufficient pam_unix.so
account required pam_permit.so
-password sufficient pam_systemd_home.so
password sufficient pam_unix.so sha512 shadow try_first_pass
password required pam_deny.so
-session optional pam_keyinit.so revoke
-session optional pam_loginuid.so
-session optional pam_systemd_home.so
-session optional pam_systemd.so
session required pam_unix.so
systemd(1), systemd-user-sessions.service(8), user@.service(5),
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)
1. JSON User Records
https://systemd.io/USER_RECORD
2. Desktop Entry Specification
https://standards.freedesktop.org/desktop-entry-spec/latest/
3. XDG Base Directory Specification
https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-02-02. (At that
time, the date of the most recent commit that was found in the
repository was 2025-02-02.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~devel PAM_SYSTEMD(8)
Pages that refer to this page: run0(1), org.freedesktop.login1(5), systemd.exec(5), user@.service(5), systemd.directives(7), systemd.index(7), systemd.system-credentials(7), pam_systemd_home(8), systemd-logind.service(8)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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