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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | HOME AREA SUPPORT | MODULE TYPES PROVIDED | ENVIRONMENT | EXAMPLE | SEE ALSO | NOTES | COLOPHON |
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PAM_SYSTEMD_HOME(8) pam_systemd_home PAM_SYSTEMD_HOME(8)
pam_systemd_home - Authenticate users and mount home directories
via systemd-homed.service
pam_systemd_home.so
pam_systemd_home ensures that home directories managed by
systemd-homed.service(8) are automatically activated (mounted) on
user login, and are deactivated (unmounted) when the last session
of the user ends. For such users, it also provides authentication
(when per-user disk encryption is used, the disk encryption key is
derived from the authentication credential supplied at login
time), account management (the JSON user record[1] embedded in the
home store contains account details), and implements the updating
of the encryption password (which is also used for user
authentication).
The following options are understood:
suspend=
Takes a boolean argument. If true, the home directory of the
user will be suspended automatically during system suspend; if
false it will remain active. Automatic suspending of the home
directory improves security substantially as secret key
material is automatically removed from memory before the
system is put to sleep and must be re-acquired (through user
re-authentication) when coming back from suspend. It is
recommended to set this parameter for all PAM applications
that have support for automatically re-authenticating via PAM
on system resume. If multiple sessions of the same user are
open in parallel the user's home directory will be left
unsuspended on system suspend as long as at least one of the
sessions does not set this parameter to on. Defaults to off.
Note that TTY logins generally do not support
re-authentication on system resume. Re-authentication on
system resume is primarily a concept implementable in
graphical environments, in the form of lock screens brought up
automatically when the system goes to sleep. This means that
if a user concurrently uses graphical login sessions that
implement the required re-authentication mechanism and console
logins that do not, the home directory is not locked during
suspend, due to the logic explained above. That said, it is
possible to set this field for TTY logins too, ignoring the
fact that TTY logins actually do not support the
re-authentication mechanism. In that case the TTY sessions
will appear hung until the user logs in on another virtual
terminal (regardless of whether via another TTY session or
graphically) which will resume the home directory and unblock
the original TTY session. (Do note that lack of screen locking
on TTY sessions means even though the TTY session appears
hung, keypresses can still be queued into it, and the existing
screen contents be read without re-authentication; this
limitation is unrelated to the home directory management
pam_systemd_home and systemd-homed.service implement.)
Turning this option on by default is highly recommended for
all sessions, but only if the service managing these sessions
correctly implements the aforementioned re-authentication.
Note that the re-authentication must take place from a
component running outside of the user's context, so that it
does not require access to the user's home directory for
operation. Traditionally, most desktop environments do not
implement screen locking this way, and need to be updated
accordingly.
This setting may also be controlled via the
$SYSTEMD_HOME_SUSPEND environment variable (see below), which
pam_systemd_home reads during initialization and sets for
sessions. If both the environment variable is set and the
module parameter specified the latter takes precedence.
Added in version 245.
debug[=]
Takes an optional boolean argument. If yes or without the
argument, the module will log debugging information as it
operates.
Added in version 245.
Home directories managed by systemd-homed.service(8) support
multiple home "areas", which are additional secondary home
directories of the user within the primary home directory. An
example: at login time if a user "lennart" with a home directory
of /home/lennart specifies "lennart%versuch1" as account name
during login, then pam_systemd_home will execute a login into
"lennart" but ensure that the $HOME variable is set to
/home/lennart/Areas/versuch1 instead of the usual /home/lennart.
This is particularly useful when sharing the same home directory
between multiple systems (for example between a host and a VM),
with the desire to share the home directory to a large degree, but
still have separate session configuration in place.
Note that the default area to log into can also be encoded in the
user record, and it can be specified among pam_systemd(8)
configuration parameters. However, an explicit area specified at
login time (via the "%" described above) overrides any such
default. Also note that simply suffixing an account with "%" at
login time (i.e. specifying an empty area name) has the effect of
ensuring a login into the primary home directory, overriding any
default area configuration via the user record or PAM.
Note that not all login mechanisms are compatible with the "%"
syntax at login time. Most notably ssh(8) is not.
Note that the area directory to log into must exist for the area
specification to be respected. If an area is specified during
login via the "%" logic (or the other mentioned mechanisms) and it
does not actually exist the request will be ignored, and the user
will log into the primary home directory instead.
Typically, in order to make use of the mechanism set up an area
first, like this:
lennart@zeta$ mkdir -p ~/Areas
lennart@zeta$ cp -av /etc/skel ~/Areas/versuch1
This should be enough to log into the newly created area, either
via a regular terminal (using "lennart%versuch1" when prompted for
a user name), or via run0(1):
lennart@zeta$ run0 --area=versuch1
The module implements all four PAM operations: auth (to allow
authentication using the encrypted data), account (because users
with systemd-homed.service user accounts are described in a JSON
user record[1] and may be configured in more detail than in the
traditional Linux user database), session (because user sessions
must be tracked in order to implement automatic release when the
last session of the user is gone), password (to change the
encryption password — also used for user authentication — through
PAM).
The following environment variables are initialized by the module
and available to the processes of the user's session:
$SYSTEMD_HOME=1
Indicates that the user's home directory is managed by
systemd-homed.service.
Added in version 245.
$SYSTEMD_HOME_SUSPEND=
Indicates whether the session has been registered with the
suspend mechanism enabled or disabled (see above). The
variable's value is either "0" or "1". Note that the module
both reads the variable when initializing, and sets it for
sessions.
Added in version 246.
Here's an example PAM configuration fragment that permits users
managed by systemd-homed.service to log in:
#%PAM-1.0
-auth [success=done authtok_err=bad perm_denied=bad maxtries=bad default=ignore] pam_systemd_home.so
auth sufficient pam_unix.so
auth required pam_deny.so
account required pam_nologin.so
-account [success=done authtok_expired=bad new_authtok_reqd=bad maxtries=bad acct_expired=bad default=ignore] pam_systemd_home.so
account required pam_unix.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-homed.service(8), homed.conf(5), homectl(1),
pam_systemd(8), pam.conf(5), pam.d(5), pam(8)
1. JSON user record
https://systemd.io/USER_RECORD/
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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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
[email protected]
systemd 258~rc2 PAM_SYSTEMD_HOME(8)
Pages that refer to this page: homectl(1), run0(1), systemd.directives(7), systemd.index(7), pam_systemd(8), systemd-homed.service(8)
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HTML rendering created 2025-09-06 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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