how to protect my process from being killed?

Question

We have a mission-critical server program on top of Linux and we don\'t want others to terminate it accidentally. If somebody terminates it or it crashes, we want it to rest

Answer 1

They would have to poll each other, typically. Have them send signal zero to each other (which just checks for aliveness and does not interrupt the other program).

echo $$>$1
read otherpid < $2
while :; do
 while kill -0 $otherpid
  do
   sleep 1
  done
 # restart other program
 # (really restarting myself in my peer configuration)
 $0 $2 $1 &
 newpid=0
 while [ "$newpid" -eq "$otherpid" ]
  do
   sleep 2
   read newpid < $2
  done
 otherpid=$newpid
done

You could go more fancy and try to do watchdog stuff to make sure that the program is not only existing, but actually running.