Namespace

operating-systems virtualisation

Definition

Namespace

A namespace is a Linux kernel abstraction that wraps a global system resource so that processes inside the namespace see an isolated instance of that resource.

Changes made to the resource are visible to other processes in the same namespace but are invisible to processes outside it.

Namespaces are the foundation of Linux OS-level virtualisation and were introduced in 2008.

Types

Namespace types

Type	Isolated resource	Example
mnt	file system mount points	each container has its own /tmp or /var
pid	process IDs	each container has its own init (PID 1) and /proc
net	network interfaces, routing, firewall	each container has its own loopback device
ipc	inter-process communication	two containers can create shared memory with the same name
uts	hostname and domain name	each container has its own hostname
cgroup	control group view	processes in a container cannot see host cgroup directories
user	user and group IDs, capabilities	root inside a container may be an unprivileged user outside

Creating namespaces

The unshare command can create a new namespace and run a program inside it.