2. EL 7
  3. util-linux
  4. unshare(1)

Scroll to navigation

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:

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.

Setting hostname or domainname will not affect the rest of the system. (CLONE_NEWUTS flag)
The process will have an independent namespace for System V message queues, semaphore sets and shared memory segments. (CLONE_NEWIPC flag)
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)
Children will have a distinct set of PID to process mappings from their parent. (CLONE_NEWPID flag)
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

Unshare the IPC namespace.
Unshare the mount namespace.
Unshare the network namespace.
Unshare the pid namespace. See also the --fork and --mount-proc options.
Unshare the UTS namespace.
Unshare the user namespace.
Fork the specified program as a child process of unshare rather than running it directly. This is useful when creating a new pid namespace.
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 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).
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 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 multiple ranges of UIDs and GIDs. This option implies --setgroups=deny.
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.
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.

Display version information and exit.
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

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@dottedmag.net>

AVAILABILITY

The unshare command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

July 2014 util-linux