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Linux 2.6 - man page for pam_namespace (linux section 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] [no_unmount_on_close]
			[use_current_context] [use_default_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 http://lwn.net/Articles/159092.

	   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 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 polyinstantiation mechanism.

	   For certain trusted programs such as newrole, open session is called from a child
	   process while the parent performs close session and pam end functions. For these
	   commands use this option to instruct pam_close_session to not unmount the bind mounted
	   polyinstantiated directory in the parent.

	   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 polyinstantiation.

       Only the session module type is provided. The module must not be called from multithreaded

	   Namespace setup was successful.

	   Unexpected system error occurred while setting up namespace.

	   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 group:

       session required pam_namespace.so [arguments]

       To use polyinstantiation with graphical display manager gdm, insert the following line,
       before exit 0, in /etc/gdm/PostSession/Default:


       This allows gdm to restart after each session and appropriately adjust namespaces of
       display manager and the X server. If polyinstantiation of /tmp is desired along with the
       graphical environment, then additional configuration changes are needed to address the
       interaction of X server and font server namespaces with their use of /tmp to create
       communication sockets. Please use the initialization script /etc/security/namespace.init
       to ensure that the X server and its clients can appropriately access the communication
       socket X0. Please refer to the sample instructions provided in the comment section of the
       instance initialization script /etc/security/namespace.init. In addition, perform the
       following changes to use graphical environment with polyinstantiation of /tmp:

		 1. Disable the use of font server by commenting out "FontPath"
		    line in /etc/X11/xorg.conf. If you do want to use the font server
		    then you will have to augment the instance initialization
		    script to appropriately provide /tmp/.font-unix from the
		    polyinstantiated /tmp.
		 2. Ensure that the gdm service is setup to use pam_namespace,
		    as described above, by modifying /etc/pam.d/gdm.
		 3. Ensure that the display manager is configured to restart X server
		    with each new session. This default setup can be verified by
		    making sure that /usr/share/gdm/defaults.conf contains
		    "AlwaysRestartServer=true", and it is not overridden by

       namespace.conf(5), pam.d(5), mount(8), pam(7).

       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>.

Linux-PAM Manual			    06/04/2011				 PAM_NAMESPACE(8)

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