How To Check Dead Process in Linux

use lsof command to check if any files deleted when processes are running

    * lsof -p PID

use strace to check the pids are not processing anything

    * time strace -p PID

use top  then H, to see all the threads

or use -m in ps

ps -efwm|grep httpd

strace -o /tmp/strace.output  -p  PID

how to check which process is taking a port
for example, apache can't start on port 80

lsof -i TCP:80