Linux PID recycling

linux pid recycle
Cygnus picture Cygnus · Jul 4, 2012 · Viewed 23.5k times · Source

Is there any policy in Linux as to the recycling of used PIDs ? I mean, if a PId has been used, how much later will it be used again ?

Answer

cnicutar picture cnicutar · Jul 4, 2012

As new processes fork in, PIDs will increase to a system-dependent limit and then wrap around. The kernel will not reuse a PID before this wrap-around happens.

The limit (maximum number of pids) is /proc/sys/kernel/pid_max. The manual says:

/proc/sys/kernel/pid_max (since Linux 2.5.34)

This file specifies the value at which PIDs wrap around (i.e., the value in this file is one greater than the maximum PID). The default value for this file, 32768, results in the same range of PIDs as on earlier kernels

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