What are the Linux Namespaces?

The kernel provides process isolation by creating separate namespaces for containers. Namespaces enable creating an abstraction of a particular global system resource and make it appear as a separated instance to processes within a namespace. Consequently, several containers can use the same resource simultaneously without creating a conflict.

Some of the namespaces in Linux

• Mount namespaces
• UTS namespaces (UNIX Timesharing System)
• IPC namespaces (Interprocess Communication)
• PID namespaces (Process Identification)
• Network namespaces

Note: Namespaces are a feature of the Linux kernel that isolates and virtualizes system resources of a collection of processes. (wikipedia)

There is another type of namespace called user namespace. User namespaces are similar to PID namespaces, they allow you to specify a range of host UIDs dedicated to the container. Consequently, a process can have full root privileges for operations inside the container, and at the same time be unprivileged for operations outside the container.

Sample overview demo

$ docker run -d alpine sleep 1000
$ sudo ls /proc/[pid]/ns/