Process Namespace

Process namespaces isolate the process ID number space, meaning that processes in different PID namespaces can have the same PID.

Process namespaces allow containers to provide functionality such as suspending/resuming the set of processes in the container and migrating the container to a new host while the processes inside the container maintain the same PIDs.

PIDs in a new PID namespace start at 1, somewhat like a standalone system, and calls to fork or clone will produce processes with PIDs that are unique within the namespace.

UNIX processes form a parent-child tree.

• Process identifiers (PIDs) are global.

The process namespace creates nested trees.

• Processes within inner namespaces cannot access processes of outer namespaces by their PID.

A process can have many PIDs.

• One for each namespace it belongs.