unshare (1)

unshare [options] program [arguments]

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 for the shared flags).

It's recommended to use mount --make-rprivate or mount --make-rslave after unshare --mount to make sure that mountpoints in the new namespace are really unshared from the parental namespace.

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.

-h, --help

Display help text and exit.

-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 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 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.

unshare(2), clone(2), mount(8)

None known so far.

Mikhail Gusarov <[email protected]>

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