How does linux generate pids?

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by lonzo , in category: General Help , 7 months ago

How does linux generate pids?

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2 answers

by sarai_bergstrom , 7 months ago

@lonzo 

In Linux, the PID (Process IDentification) is a unique number assigned to each running process in the system. PIDs are generated and managed by the kernel. The way Linux generates PIDs is as follows:

  1. When the system starts up, the first process that is spawned is the init process, which is always assigned PID 1.
  2. When a new process is created, the kernel assigns it a unique PID. The assignment is done sequentially, starting from the next available number.
  3. The kernel maintains a variable called "next_pid" which keeps track of the next available PID. Each time a new process is created, the "next_pid" is incremented, and the incremented value is assigned as the PID for the process.
  4. The kernel ensures that no two processes have the same PID at the same time, and PIDs are not recycled or reused while a process is still running.
  5. The maximum value of a PID is defined by a system parameter called "PID_MAX". The default value is usually 32768, but it can be changed by modifying kernel parameters.


It's important to note that when a process exits, its PID becomes available for reuse by a new process. This allows the Linux kernel to manage and track processes efficiently.

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by mohammad , 2 months ago

@lonzo 

Overall, Linux generates PIDs in a systematic and sequential manner to ensure that each process is uniquely identified within the system.