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 exe‐
cutes the specified program. The namespaces to be unshared are indi‐
cated via options. Unshareable namespaces are:
mount namespace
Mounting and unmounting filesystems will not affect the rest of
the system (CLONENEWNS 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 propa‐
gation unchanged. Note that private is the kernel default.
UTS namespace
Setting hostname or domainname will not affect the rest of the
system. (CLONENEWUTS flag)
IPC namespace
The process will have an independent namespace for System V mes‐
sage queues, semaphore sets and shared memory segments.
(CLONENEWIPC flag)
network namespace
The process will have independent IPv4 and IPv6 stacks, IP rout‐
ing tables, firewall rules, the /proc/net and /sys/class/net
directory trees, sockets, etc. (CLONENEWNET flag)
pid namespace
Children will have a distinct set of PID to process mappings
from their parent. (CLONENEWPID flag)
user namespace
The process will have a distinct set of UIDs, GIDs and capabili‐
ties. (CLONENEWUSER 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 creating a new mount names‐
pace since the /proc mount would otherwise mess up existing pro‐
grams on the system. The new proc filesystem is explicitly
mounted as private (by MSPRIVATE|MSREC).
-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 sophisticated use cases, such as mapping
multiple ranges of UIDs and GIDs. This option implies set‐
groups=deny.
propagation private|shared|slave|unchanged
Recursively sets mount propagation flag in the new mount names‐
pace. 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 CAPSETGID and CAPSETGID 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
permanently 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
AVAILABILITY
The unshare command is part of the util-linux package and is available
from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
util-linux July 2014 UNSHARE(1)