namespace.conf(5) — Linux manual page


NAMESPACE.CONF(5)           Linux-PAM Manual           NAMESPACE.CONF(5)

NAME         top

       namespace.conf - the namespace configuration file

DESCRIPTION         top

       The 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 an instance directory is
       set up and mounted. 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

       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.

       mntopts=value - value of this flag is passed to the mount call
       when the tmpfs mount is done. It allows for example the
       specification of the maximum size of the tmpfs instance that is
       created by the mount call. In addition to options specified in
       the tmpfs(5) manual the nosuid, noexec, and nodev flags can be
       used to respectively disable setuid bit effect, disable running
       executables, and disable devices to be interpreted on the mounted
       tmpfs filesystem.

       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

       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 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

EXAMPLES         top

       These are some example lines which might be specified in

                 # 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 [arguments]

       This module also depends on setting the context.

SEE ALSO         top

       pam_namespace(8), pam.d(5), pam(8)

AUTHORS         top

       The namespace.conf manual page was written by Janak Desai
       <>. More features added by Tomas Mraz

COLOPHON         top

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Linux-PAM Manual               12/22/2023              NAMESPACE.CONF(5)

Pages that refer to this page: pam_namespace(8)