DragonOS/docs/locales/en/kernel/container/namespaces/pid_namespace.md

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Process Namespace

:::{note} Author: Cao Fengyi 1553389239@qq.com

October 30, 2024 :::

pid_namespace is a type of namespace in the kernel that is used to achieve process isolation. It allows processes running in different namespaces to have independent views of process IDs (PIDs).

Underlying Architecture

pcb -> nsproxy -> pid_namespace

• pid_namespace contains an independent set of process allocators and an orphan process reaper, which independently manages PIDs within the namespace.
• Detailed information about processes is stored in the proc file system. The information corresponding to a specific PID is located within the pid_namespace, recording information related to the pid_namespace.
• The limitations imposed by pid_namespace are controlled and managed by ucount.

System Call Interface

• clone
  • CLONE_NEWPID is used to create a new PID namespace. When this flag is used, the child process will run in the new PID namespace, with the process ID starting from 1.
• unshare
  • After calling unshare() with the CLONE_NEWPID flag, all subsequent child processes will run within the new namespace.
• getpid
  • Calling getpid() within a namespace returns the process ID of the process within the current PID namespace.