Linux is a multitasking operating system. Linux creates a process whenever a program is launched, either by user or by OS itself.
If a process runs and terminates properly, then everything is fine. If not, You need to manage the processes by commands.
If we would like to get a snapshot of what is currently happening on the system we may use a program called top
Type of processes:
Foreground Processes: They run on the screen and need input from the user.
Background Processes: They run in the background and usually do not need user input.
Let’s start with a process management commands.
ps To display the currently working processes
$ ps PID TTY TIME CMD 2896 pts/0 00:00:00 bash 2911 pts/0 00:00:00 ps
Display all processes
$ ps ax PID TTY STAT TIME COMMAND 1 ? Ss 0:04 /sbin/init 2 ? S 0:00 [kthreadd] 3 ? S 0:00 [migration/0] 4 ? S 0:00 [ksoftirqd/0] 5 ? S 0:00 [migration/0] 6 ? S 0:00 [watchdog/0] 7 ? S 0:00 [migration/1]
$ ps -ef
Use the “u” option or “-f” option to display detailed information about the processes
$ ps aux $ ps -ef -f
Display process by user
$ ps -f -u ops
Show process by name
$ ps -C metacity
Show process by process id
$ ps -f -p 2609,2704,2585
Show process by using grep (searching)
$ ps -ef |grep "metacity"
Show process by sorting on cpu usage percentage
$ ps aux --sort=-pcpu,+pmem |head
Customizing the ps output format
$ ps -eo uname,pid,start_time,time,args |head
top Display all running process
kill pid terminate a process
$ kill -9 2895
killall proc Kill all the process named proc
$ killall -9 firefox
pkill pattern Will kill all processes matching the pattern
$ pkill -USR1 sample
bg List stopped or background jobs,resume a stopped job in the background
fg Brings the most recent job to foreground