|
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. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | MODULE TYPES PROVIDED | RETURN VALUES | FILES | EXAMPLES | SEE ALSO | AUTHORS | COLOPHON |
|
|
|
PAM_NAMESPACE(8) Linux-PAM Manual PAM_NAMESPACE(8)
pam_namespace - PAM module for configuring namespace for a session
pam_namespace.so [debug] [unmnt_remnt] [unmnt_only]
[require_selinux] [gen_hash]
[ignore_config_error]
[ignore_instance_parent_mode] [unmount_on_close]
[use_current_context] [use_default_context]
[mount_private]
The pam_namespace PAM module sets up a private namespace for a
session with polyinstantiated directories. A polyinstantiated
directory provides a different instance of itself based on user
name, or when using SELinux, user name, security context or both.
If an executable script /etc/security/namespace.init exists, it is
used to initialize the instance directory after it is set up and
mounted on the polyinstantiated directory. The script receives the
polyinstantiated directory path, the instance directory path, flag
whether the instance directory was newly created (0 for no, 1 for
yes), and the user name as its arguments.
The pam_namespace module disassociates the session namespace from
the parent namespace. Any mounts/unmounts performed in the parent
namespace, such as mounting of devices, are not reflected in the
session namespace. To propagate selected mount/unmount events from
the parent namespace into the disassociated session namespace, an
administrator may use the special shared-subtree feature. For
additional information on shared-subtree feature, please refer to
the mount(8) man page and the shared-subtree description at
http://lwn.net/Articles/159077 and http://lwn.net/Articles/159092.
debug
A lot of debug information is logged using syslog
unmnt_remnt
For programs such as su and newrole, the login session has
already setup a polyinstantiated namespace. For these
programs, polyinstantiation is performed based on new user id
or security context, however the command first needs to undo
the polyinstantiation performed by login. This argument
instructs the command to first undo previous polyinstantiation
before proceeding with new polyinstantiation based on new
id/context
unmnt_only
For trusted programs that want to undo any existing bind
mounts and process instance directories on their own, this
argument allows them to unmount currently mounted instance
directories
require_selinux
If selinux is not enabled, return failure
gen_hash
Instead of using the security context string for the instance
name, generate and use its md5 hash.
ignore_config_error
If a line in the configuration file corresponding to a
polyinstantiated directory contains format error, skip that
line process the next line. Without this option, pam will
return an error to the calling program resulting in
termination of the session.
ignore_instance_parent_mode
Instance parent directories by default are expected to have
the restrictive mode of 000. Using this option, an
administrator can choose to ignore the mode of the instance
parent. This option should be used with caution as it will
reduce security and isolation goals of the polyinstantiation
mechanism.
unmount_on_close
Explicitly unmount the polyinstantiated directories instead of
relying on automatic namespace destruction after the last
process in a namespace exits. This option should be used only
in case it is ensured by other means that there cannot be any
processes running in the private namespace left after the
session close. It is also useful only in case there are
multiple pam session calls in sequence from the same process.
use_current_context
Useful for services which do not change the SELinux context
with setexeccon call. The module will use the current SELinux
context of the calling process for the level and context
polyinstantiation.
use_default_context
Useful for services which do not use pam_selinux for changing
the SELinux context with setexeccon call. The module will use
the default SELinux context of the user for the level and
context polyinstantiation.
mount_private
This option can be used on systems where the / mount point or
its submounts are made shared (for example with a mount
--make-rshared / command). The module will mark the whole
directory tree so any mount and unmount operations in the
polyinstantiation namespace are private. Normally the
pam_namespace will try to detect the shared / mount point and
make the polyinstantiated directories private automatically.
This option has to be used just when only a subtree is shared
and / is not.
Note that mounts and unmounts done in the private namespace
will not affect the parent namespace if this option is used or
when the shared / mount point is autodetected.
Only the session module type is provided. The module must not be
called from multithreaded processes.
PAM_SUCCESS
Namespace setup was successful.
PAM_SERVICE_ERR
Unexpected system error occurred while setting up namespace.
PAM_SESSION_ERR
Unexpected namespace configuration error occurred.
/etc/security/namespace.conf
Main configuration file
/etc/security/namespace.d
Directory for additional configuration files
/etc/security/namespace.init
Init script for instance directories
For the <service>s you need polyinstantiation (login for example)
put the following line in /etc/pam.d/<service> as the last line
for session group:
session required pam_namespace.so [arguments]
To use polyinstantiation with graphical display manager gdm,
please refer to gdm's documentation.
namespace.conf(5), pam.d(5), mount(8), pam(8).
The namespace setup scheme was designed by Stephen Smalley, Janak
Desai and Chad Sellers. The pam_namespace PAM module was developed
by Janak Desai <janak@us.ibm.com>, Chad Sellers
<csellers@tresys.com> and Steve Grubb <sgrubb@redhat.com>.
Additional improvements by Xavier Toth <txtoth@gmail.com> and
Tomas Mraz <tmraz@redhat.com>.
This page is part of the linux-pam (Pluggable Authentication
Modules for Linux) project. Information about the project can be
found at ⟨http://www.linux-pam.org/⟩. If you have a bug report
for this manual page, see ⟨//www.linux-pam.org/⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/linux-pam/linux-pam.git⟩ on 2023-12-22. (At
that time, the date of the most recent commit that was found in
the repository was 2023-12-18.) 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
Linux-PAM Manual 12/22/2023 PAM_NAMESPACE(8)
Pages that refer to this page: namespace.conf(5), mount_namespaces(7), pam_namespace_helper(8)
|
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. |
|