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NAME | DESCRIPTION | EXAMPLES | SEE ALSO | AUTHORS | COLOPHON |
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NAMESPACE.CONF(5) Linux-PAM Manual NAMESPACE.CONF(5)
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 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
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
/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.
pam_namespace(8), pam.d(5), pam(8)
The namespace.conf manual page was written by Janak Desai
<[email protected]>. More features added by Tomas Mraz
<[email protected]>.
This page is part of the linux-pam (Pluggable Authentication
Modules for Linux) project. Information about the project can be
found at ⟨http://www.linux-pam.org/⟩. If you have a bug report
for this manual page, see ⟨//www.linux-pam.org/⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/linux-pam/linux-pam.git⟩ on 2023-12-22. (At
that time, the date of the most recent commit that was found in
the repository was 2023-12-18.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Linux-PAM Manual 12/22/2023 NAMESPACE.CONF(5)
Pages that refer to this page: pam_namespace(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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