What is the kernel.pid_max parameter and how can a low value affect it?

The kernel.pid_max parameter in Linux defines the maximum process ID (PID) value that can be assigned to a process in the system. By default, this value is usually around 32768 or higher, but it can be increased to several million.

If kernel.pid_max is set too low, it limits the number of processes that can exist simultaneously in the system. As a result, when this limit is reached, new processes cannot be created, leading to startup errors and potential service hangs.

For example, if you have many parallel tasks or containers, and pid_max is too small, the system will quickly exhaust available PIDs, negatively affecting stability.

You can check the current value with the command:

cat /proc/sys/kernel/pid_max

To temporarily change it (until reboot):

sudo sysctl -w kernel.pid_max=131072

For permanent changes, add the following to /etc/sysctl.conf:

kernel.pid_max = 131072

It is recommended to set the value with a margin, considering the load and the number of processes in the system.