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 names‐
paces 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, semaphore 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.
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 capabili‐
ties needed to manage various aspects of the newly created namespaces (such as configuring interfaces
in the network 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 multi‐
ple 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 propaga‐
tion 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 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 <[email protected]>
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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