Linux 101 : Maximum number of processes - pid_max -

When the system boots up, the first process with PID=1 starts, which is systemd - it is usually a symbolic link to "/sbin/init" -.

This parent process spawns other processes, which in turn spawn others with higher PID numbers.

The PID on a system can't go beyond a certain number defined in the file "/proc/sys/kernel/pid_max".

We could check this value using the below command:


We could change the pid_max value to 20000 using the below command:

We could do it also by writing the value directly in the below file:


When the maximum number of PID is reached, the system goes back to using the lowest values available.


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