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 namespace every time a new instance
      directory is setup. 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.
      The pam_namespace.so module allows setup of
      private namespaces with polyinstantiated directories.
      Directories can be polyinstantiated based on user name
      or, in the case of SELinux, user name, sensitivity level or complete security context.  If an
      executable script /etc/security/namespace.init
      exists, it is used to initialize the namespace every time a new instance
      directory is setup. The script receives the polyinstantiated
      directory path and the instance directory path as its arguments.
    
      The /etc/security/namespace.conf file specifies
      which directories are polyinstantiated, how they are polyinstantiated,
      how instance directories would be named, and any users for whom
      polyinstantiation would not be performed.
    
      When someone logs in, the file namespace.conf is
      scanned. Comments are marked by # characters.
      Each non comment line represents one polyinstantiated
      directory. The fields are separated by spaces but can be quoted by
      " characters also escape
      sequences \b, \n, and
      \t are recognized. The fields are as follows:
   
polydir instance_prefix method list_of_uids
    
      The first field, polydir, is the absolute
      pathname of the directory to polyinstantiate. The special string
      $HOME is replaced with the user's home directory,
      and $USER with the username. This field cannot
      be blank.
    
      The second field, instance_prefix is
      the string prefix used to build the pathname for the instantiation
      of <polydir>. Depending on the polyinstantiation 
      method it is then appended with
      "instance differentiation string" to generate the final
      instance directory path. This directory is created if it did not exist
      already, and is then bind mounted on the <polydir> to provide an
      instance of <polydir> based on the <method> column.
      The special string $HOME is replaced with the
      user's home directory, and $USER with the username.
      This field cannot be blank.
    
      The third field, method, is the method
      used for polyinstantiation. It can take these values; "user"
      for polyinstantiation based on user name, "level" for 
      polyinstantiation based on process MLS level and user name, "context" for
      polyinstantiation based on process security context and user name,
      "tmpfs" for mounting tmpfs filesystem as an instance dir, and
      "tmpdir" for creating temporary directory as an instance dir which is
      removed when the user's session is closed.
      Methods "context" and "level" are only available with SELinux. This
      field cannot be blank.
    
      The fourth field, list_of_uids, is
      a comma separated list of user names for whom the polyinstantiation
      is not performed. If left blank, polyinstantiation will be performed
      for all users. If the list is preceded with a single "~" character,
      polyinstantiation is performed only for users in the list.
    
      The method field can contain also following
      optional flags separated by : characters.
    
create=mode,owner,group
      - create the polyinstantiated directory. The mode, owner and group parameters
      are optional. The default for mode is determined by umask, the default
      owner is the user whose session is opened, the default group is the
      primary group of the user.
    
iscript=path
      - path to the instance directory init script. The base directory for relative
      paths is /etc/security/namespace.d.
    
noinit - instance directory init script will not be executed.
shared - the instance directories for "context" and "level" methods will not contain the user name and will be shared among all users.
The directory where polyinstantiated instances are to be created, must exist and must have, by default, the mode of 0000. The requirement that the instance parent be of mode 0000 can be overridden with the command line option ignore_instance_parent_mode
      In case of context or level polyinstantiation the SELinux context
      which is used for polyinstantiation is the context used for executing
      a new process as obtained by getexeccon. This context must be set
      by the calling application or pam_selinux.so
      module. If this context is not set the polyinstatiation will be
      based just on user name.
    
The "instance differentiation string" is <user name> for "user" method and <user name>_<raw directory context> for "context" and "level" methods. If the whole string is too long the end of it is replaced with md5sum of itself. Also when command line option gen_hash is used the whole string is replaced with md5sum of itself.
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.
no_unmount_on_close
        For certain trusted programs such as newrole, open session is called from a child process while the parent perfoms 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.
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.
      The session service is supported. The module must not
      be called from multithreaded processes.
    
Namespace setup was successful.
Unexpected system error occurred while setting up namespace.
Unexpected namespace configuration error occurred.
/etc/security/namespace.confMain configuration file
/etc/security/namespace.dDirectory for additional configuration files
/etc/security/namespace.initInit script for instance directories
      These are some example lines which might be specified in
      /etc/security/namespace.conf.
    
      # The following three lines will polyinstantiate /tmp,
      # /var/tmp and user's home directories. /tmp and /var/tmp
      # will be polyinstantiated based on the security level
      # as well as user name, whereas home directory will be
      # polyinstantiated based on the full security context and user name.
      # Polyinstantiation will not be performed for user root
      # and adm for directories /tmp and /var/tmp, whereas home
      # directories will be polyinstantiated for all users.
      #
      # Note that instance directories do not have to reside inside
      # the polyinstantiated directory. In the examples below,
      # instances of /tmp will be created in /tmp-inst directory,
      # where as instances of /var/tmp and users home directories
      # will reside within the directories that are being
      # polyinstantiated.
      #
      /tmp     /tmp-inst/               level      root,adm
      /var/tmp /var/tmp/tmp-inst/   	level      root,adm
      $HOME    $HOME/$USER.inst/inst- context
    
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]
This module also depends on pam_selinux.so setting the context.
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>.