pam_namespace(8) — Linux manual page


PAM_NAMESPACE(8)            Linux-PAM Manual            PAM_NAMESPACE(8)

NAME         top

       pam_namespace - PAM module for configuring namespace for a

SYNOPSIS         top [debug] [unmnt_remnt] [unmnt_only]
                        [require_selinux] [gen_hash]
                        [ignore_instance_parent_mode] [unmount_on_close]
                        [use_current_context] [use_default_context]

DESCRIPTION         top

       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

       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 and

OPTIONS         top

           A lot of debug information is logged using syslog

           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

           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

           If selinux is not enabled, return failure

           Instead of using the security context string for the instance
           name, generate and use its md5 hash.

           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.

           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

           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.

           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

           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.

           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.

RETURN VALUES         top

           Namespace setup was successful.

           Unexpected system error occurred while setting up namespace.

           Unexpected namespace configuration error occurred.

FILES         top

           Main configuration file

           Directory for additional configuration files

           Init script for instance directories

EXAMPLES         top

       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 [arguments]

       To use polyinstantiation with graphical display manager gdm,
       please refer to gdm's documentation.

SEE ALSO         top

       namespace.conf(5), pam.d(5), mount(8), pam(8).

AUTHORS         top

       The namespace setup scheme was designed by Stephen Smalley, Janak
       Desai and Chad Sellers. The pam_namespace PAM module was
       developed by Janak Desai <>, Chad Sellers
       <> and Steve Grubb <>.
       Additional improvements by Xavier Toth <> and
       Tomas Mraz <>.

COLOPHON         top

       This page is part of the linux-pam (Pluggable Authentication
       Modules for Linux) project.  Information about the project can be
       found at ⟨⟩.  If you have a bug report
       for this manual page, see ⟨//⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ 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

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)