nsenter - Man Page

run program in different namespaces

Examples (TL;DR)

Synopsis

nsenter [options] [program [arguments]]

Description

The nsenter command executes program in the namespace(s) that are specified in the command-line options (described below). If program is not given, then “${SHELL}” is run (default: /bin/sh).

Enterable namespaces are:

mount namespace

Mounting and unmounting filesystems will not affect the rest of the system, except for filesystems which are explicitly marked as shared (with mount --make-shared; see /proc/self/mountinfo for the shared flag). For further details, see mount_namespaces(7) and the discussion of the CLONE_NEWNS flag in clone(2).

UTS namespace

Setting hostname or domainname will not affect the rest of the system. For further details, see uts_namespaces(7).

IPC namespace

The process will have an independent namespace for POSIX message queues as well as System V message queues, semaphore sets and shared memory segments. For further details, see ipc_namespaces(7).

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. For further details, see network_namespaces(7).

PID namespace

Children will have a set of PID to process mappings separate from the nsenter process. nsenter will fork by default if changing the PID namespace, so that the new program and its children share the same PID namespace and are visible to each other. If --no-fork is used, the new program will be exec'ed without forking. For further details, see pid_namespaces(7).

user namespace

The process will have a distinct set of UIDs, GIDs and capabilities. For further details, see user_namespaces(7).

cgroup namespace

The process will have a virtualized view of /proc/self/cgroup, and new cgroup mounts will be rooted at the namespace cgroup root. For further details, see cgroup_namespaces(7).

time namespace

The process can have a distinct view of CLOCK_MONOTONIC and/or CLOCK_BOOTTIME which can be changed using /proc/self/timens_offsets. For further details, see time_namespaces(7).

Options

Various of the options below that relate to namespaces take an optional file argument. This should be one of the /proc/[pid]/ns/* files described in namespaces(7), or the pathname of a bind mount that was created on one of those files.

-a,  --all

Enter all namespaces of the target process by the default /proc/[pid]/ns/* namespace paths. The default paths to the target process namespaces may be overwritten by namespace specific options (e.g., --all --mount=[path]).

The user namespace will be ignored if the same as the caller's current user namespace. It prevents a caller that has dropped capabilities from regaining those capabilities via a call to setns().  See setns(2) for more details.

-t,  --target pid

Specify a target process to get contexts from.  The paths to the contexts specified by pid are:

/proc/pid/ns/mnt

the mount namespace

/proc/pid/ns/uts

the UTS namespace

/proc/pid/ns/ipc

the IPC namespace

/proc/pid/ns/net

the network namespace

/proc/pid/ns/pid

the PID namespace

/proc/pid/ns/user

the user namespace

/proc/pid/ns/cgroup

the cgroup namespace

/proc/pid/ns/time

the time namespace

/proc/pid/root

the root directory

/proc/pid/cwd

the working directory respectively

-m,  --mount[=file]

Enter the mount namespace.  If no file is specified, enter the mount namespace of the target process. If file is specified, enter the mount namespace specified by file.

-u,  --uts[=file]

Enter the UTS namespace.  If no file is specified, enter the UTS namespace of the target process. If file is specified, enter the UTS namespace specified by file.

-i,  --ipc[=file]

Enter the IPC namespace.  If no file is specified, enter the IPC namespace of the target process. If file is specified, enter the IPC namespace specified by file.

-n,  --net[=file]

Enter the network namespace.  If no file is specified, enter the network namespace of the target process. If file is specified, enter the network namespace specified by file.

-p,  --pid[=file]

Enter the PID namespace.  If no file is specified, enter the PID namespace of the target process. If file is specified, enter the PID namespace specified by file.

-U,  --user[=file]

Enter the user namespace.  If no file is specified, enter the user namespace of the target process. If file is specified, enter the user namespace specified by file. See also the --setuid and --setgid options.

-C,  --cgroup[=file]

Enter the cgroup namespace.  If no file is specified, enter the cgroup namespace of the target process. If file is specified, enter the cgroup namespace specified by file.

-T,  --time[=file]

Enter the time namespace.  If no file is specified, enter the time namespace of the target process. If file is specified, enter the time namespace specified by file.

-G,  --setgid gid

Set the group ID which will be used in the entered namespace and drop supplementary groups. nsenter(1) always sets GID for user namespaces, the default is 0.

-S,  --setuid uid

Set the user ID which will be used in the entered namespace. nsenter(1) always sets UID for user namespaces, the default is 0.

--preserve-credentials

Don't modify UID and GID when enter user namespace. The default is to drops supplementary groups and sets GID and UID to 0.

-r,  --root[=directory]

Set the root directory.  If no directory is specified, set the root directory to the root directory of the target process.  If directory is specified, set the root directory to the specified directory.

-w,  --wd[=directory]

Set the working directory.  If no directory is specified, set the working directory to the working directory of the target process.  If directory is specified, set the working directory to the specified directory.

-F,  --no-fork

Do not fork before exec'ing the specified program.  By default, when entering a PID namespace, nsenter calls fork before calling exec so that any children will also be in the newly entered PID namespace.

-Z,  --follow-context

Set the SELinux security context used for executing a new process according to already running process specified by --target PID. (The util-linux has to be compiled with SELinux support otherwise the option is unavailable.)

-V,  --version

Display version information and exit.

-h,  --help

Display help text and exit.

Authors

Eric Biederman
Karel Zak

See Also

clone(2), setns(2), namespaces(7)

Availability

The nsenter command is part of the util-linux package and is available from Linux Kernel Archive.

Referenced By

ipc_namespaces(7), lsns(8), namespaces(7), network_namespaces(7), setns(2), time_namespaces(7), unshare(1), uts_namespaces(7).

June 2013 util-linux