This blog lists some important Linux Admin commands useful for monitoring Linux processes.
List All Processes
We can use the ps command to list the processes in the Linux system.
~$ ps
PID TTY TIME CMD
1116 pts/1 00:00:00 bash
2271 pts/1 00:00:00 ps
List All Processes in Detail
Let’s check all the processes in detail by their memory and consumption. We use the ps aux command for that.
Syntax: $ps aux
a = show processes for all users
u = displays the process listed by their user names/owners
x = show processes not attached to a terminal. It includes processes such as services like crond, upowerd, etc.
hduser@hmaster:~$ ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.4 0.0 37840 5784 ? Ss 18:27 0:02
hduser 1484 6.6 3.2 2787916 244508 ? Sl 18:32 0:10 /usr/lib/jvm/java-8-oracle/bin/jaroot 1799 0.0 0.0 0 0 ? R 18:32 0:00 [kworker/u256:0]
hduser 1891 5.6 2.4 2781908 183660 ? Sl 18:32 0:08 /usr/lib/jvm/java-8-oracle/bin/jahduser 2137 4.4 2.3 2750992 177272 ? Sl 18:32 0:06 /usr/lib/jvm/java-8-oracle/bin/jahduser 2278 0.0 0.0 37364 3284 pts/1 R+ 18:34 0:00 ps aux
System Uptime
We can check the system Uptime using the uptime command. It gives information about the current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.
~$ uptime
18:53:33 up 26 min, 3 users, load average: 0.00, 0.04, 0.054
# Use -p option to display information in Preety format
~$uptime -p
up 26 minutes
Kill/Terminate a process
We use the Kill command on Linux to kill or terminate a process.
Syntax:
~$kill [options] <pid>
Example:
~$kill 18766
We can also kill the process forcefully using option -9.
Example:
~$kill -9 18766
Clearing the terminal
If you have a lot of clutter on the screen and want to clear the information on the existing screen, use the clear command.
~$clear
Check if a Linux Script is running or not
Syntax:
~$pgrep(1) -fl <Name of Script>
Monitor all running process
We use top command to monitor all running processes.
~$top
top - 21:52:54 up 3:24, 3 users, load average: 0.11, 0.04, 0.01
top - 21:52:57 up 3:24, 3 users, load average: 0.10, 0.04, 0.01
%Cpu(s): 0.1 us, 0.2 sy, 0.0 ni, 99.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu(s): 0.0 us, 0.1 sy, 0.0 ni, 99.9 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 7603884 total, 5503320 free, 1637416 used, 463148 buff/cache
KiB Swap: 3913724 total, 3913724 free, 0 used. 5685176 avail Mem
1233 hduser 20 0 2962148 365388 23412 S 1.0 4.8 2:46.57 java
1233 hduser 20 0 2962148 365388 23412 S 0.7 4.8 2:46.59 java
1372 hduser 20 0 2820388 366996 23732 S 0.7 4.8 1:18.42 java
1 root 20 0 37840 5800 3884 S 0.0 0.1 0:02.32 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.02 kthreadd
$w :List Users processes
~~$ps -ef :Shows list of files and directories with PID no
~$ps -ef|grep jps :Search jps from linux machine and shows its PID number
~$ps -ef |grep 2490 :Search which PID is for what Process
~$bg :Shows the jobs running in background and suspended jobs
Checking the memory on Linux
We use the free command to check the memory on Linux. We can use the different options to display the memory in a different format.
~$free - see amount of used and free memory
Options : -m : memory in megabytes
-g :memory in gigabytes
-k :amounts in Kilobytes
-t :Displays line showing column totals
-c :Count the result times .Need to pass the -s option
-S continuously display the result second apart
~$ free
total used free shared buff/cache available
Mem: 7603884 1405440 5745632 9160 452812 5917308
Swap: 3913724 0 3913724
~$ free -m
total used free shared buff/cache available
Mem: 7425 1372 5610 8 442 5778
Swap: 3821 0 3821