How to suspend and resume processes

You can use kill to stop the process.

For a 'polite' stop to the process (prefer this for normal use), send SIGTSTP:

kill -TSTP [pid]

For a 'hard' stop, send SIGSTOP:

kill -STOP [pid]

Note that if the process you are trying to stop by PID is in your shell's job table, it may remain visible there, but terminated, until the process is fg'd again.

To resume execution of the process, sent SIGCONT:

kill -CONT [pid]

You should use the kill command for that.

To be more verbose - you have to specify the right signal, i.e.

$ kill -TSTP $PID_OF_PROCESS

for suspending the process and

$ kill -CONT $PID_OF_PROCESS

for resuming it. Documented here.