namespace.conf - the namespace configuration file
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 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 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
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
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
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.
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
/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
session required pam_namespace.so [arguments]
This module also depends on pam_selinux.so setting the context.
pam_namespace(8), pam.d(5), pam(7)
The namespace.conf manual page was written by Janak Desai
<email@example.com>. More features added by Tomas Mraz