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]
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
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
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
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
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 polyinstantiation.
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
Only the session module type is provided. The module must not be called
from multithreaded processes.
This option can be used on systems where the / mount
point or its submounts are made shared (for example with a mount
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.
Namespace setup was successful.
Unexpected system error occurred while setting up
Unexpected namespace configuration error occurred.
Main configuration file
Directory for additional configuration files
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
session required pam_namespace.so [arguments]
To use polyinstantiation with graphical display manager gdm,
please refer to gdm's documentation.
The namespace setup scheme was designed by Stephen Smalley, Janak Desai and Chad
Sellers. The pam_namespace PAM module was developed by Janak Desai
<firstname.lastname@example.org>, Chad Sellers <email@example.com> and Steve
Grubb <firstname.lastname@example.org>. Additional improvements by Xavier Toth
<email@example.com> and Tomas Mraz <firstname.lastname@example.org>.