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UNSHARE(1) User Commands UNSHARE(1)
NAME
unshare - run program with some namespaces unshared from parent
SYNOPSIS
unshare [options] program [arguments]
DESCRIPTION
Unshares the indicated namespaces from the parent process and then executes the specified
program. The namespaces to be unshared are indicated via options. Unshareable namespaces
are:
mount namespace
Mounting and unmounting filesystems will not affect the rest of the system
(CLONE_NEWNS flag), except for filesystems which are explicitly marked as shared
(with mount --make-shared; see /proc/self/mountinfo or findmnt -o+PROPAGATION for
the shared flags).
unshare automatically sets propagation to private in the new mount namespace to
make sure that the new namespace is really unshared. This feature is possible to
disable by option --propagation unchanged. Note that private is the kernel
default.
UTS namespace
Setting hostname or domainname will not affect the rest of the system.
(CLONE_NEWUTS flag)
IPC namespace
The process will have an independent namespace for System V message queues, sema-
phore sets and shared memory segments. (CLONE_NEWIPC flag)
network namespace
The process will have independent IPv4 and IPv6 stacks, IP routing tables, firewall
rules, the /proc/net and /sys/class/net directory trees, sockets, etc.
(CLONE_NEWNET flag)
pid namespace
Children will have a distinct set of PID to process mappings from their parent.
(CLONE_NEWPID flag)
user namespace
The process will have a distinct set of UIDs, GIDs and capabilities.
(CLONE_NEWUSER flag)
See clone(2) for the exact semantics of the flags.
OPTIONS
-i, --ipc
Unshare the IPC namespace.
-m, --mount
Unshare the mount namespace.
-n, --net
Unshare the network namespace.
-p, --pid
Unshare the pid namespace. See also the --fork and --mount-proc options.
-u, --uts
Unshare the UTS namespace.
-U, --user
Unshare the user namespace.
-f, --fork
Fork the specified program as a child process of unshare rather than running it
directly. This is useful when creating a new pid namespace.
--mount-proc[=mountpoint]
Just before running the program, mount the proc filesystem at mountpoint (default
is /proc). This is useful when creating a new pid namespace. It also implies cre-
ating a new mount namespace since the /proc mount would otherwise mess up existing
programs on the system. The new proc filesystem is explicitly mounted as private
(by MS_PRIVATE|MS_REC).
-r, --map-root-user
Run the program only after the current effective user and group IDs have been
mapped to the superuser UID and GID in the newly created user namespace. This
makes it possible to conveniently gain capabilities needed to manage various
aspects of the newly created namespaces (such as configuring interfaces in the net-
work namespace or mounting filesystems in the mount namespace) even when run
unprivileged. As a mere convenience feature, it does not support more sophisti-
cated use cases, such as mapping multiple ranges of UIDs and GIDs. This option
implies --setgroups=deny.
--propagation private|shared|slave|unchanged
Recursively sets mount propagation flag in the new mount namespace. The default is
to set the propagation to private, this feature is possible to disable by unchanged
argument. The options is silently ignored when mount namespace (--mount) is not
requested.
--setgroups allow|deny
Allow or deny setgroups(2) syscall in user namespaces.
setgroups(2) is only callable with CAP_SETGID and CAP_SETGID in a user namespace
(since Linux 3.19) does not give you permission to call setgroups(2) until after
GID map has been set. The GID map is writable by root when setgroups(2) is enabled
and GID map becomes writable by unprivileged processes when setgroups(2) is perma-
nently disabled.
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
EXAMPLES
# unshare --fork --pid --mount-proc readlink /proc/self
1
Establish a PID namespace, ensure we're PID 1 in it against newly mounted procfs
instance.
$ unshare --map-root-user --user sh -c whoami
root
Establish a user namespace as an unprivileged user with a root user within it.
SEE ALSO
unshare(2), clone(2), mount(8)
BUGS
None known so far.
AUTHOR
Mikhail Gusarov <dottedmag AT dottedmag.net>
AVAILABILITY
The unshare command is part of the util-linux package and is available from ftp://ftp.ker-
nel.org/pub/linux/utils/util-linux/.
util-linux July 2014 UNSHARE(1)
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