Linux System Monitoring Commands

Linux System Monitoring Commands

#1: top – Process Activity Command

Commonly Used Hot Keys

The top command provides several useful hot keys:
Hot Key Usage
t Displays summary information off and on.
m Displays memory information off and on.
A Sorts the display by top consumers of various system resources. Useful for quick identification of performance-hungry tasks on a system.
f Enters an interactive configuration screen for top. Helpful for setting up top for a specific task.
o Enables you to interactively select the ordering within top.
r Issues renice command.
k Issues kill command.
z Turn on or off color/mono

What are the CPU states found in “top” output?
Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st

# us -> User CPU time: The time the CPU has spent running users’ processes that are not niced.
# sy -> System CPU time: The time the CPU has spent running the kernel and its processes.
# ni -> Nice CPU time: The time the CPU has spent running users’ process that have been niced.
# wa -> iowait: Amount of time the CPU has been waiting for I/O to complete.
# hi -> Hardware IRQ: The amount of time the CPU has been servicing hardware interrupts.
# si -> Software Interrupts.: The amount of time the CPU has been servicing software interrupts.

#2: vmstat – System Activity, Hardware and System Information

The command vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.

vmstat 3

Display Memory Utilization Slabinfo

# vmstat -m

Tail, Vmstat and Date in Loop, Output every 10 Sec
# vmstat 1 1;for ((;;));do date; vmstat 10 2 | tail -n1;done

3: w – Find Out Who Is Logged on And What They Are Doing

w command displays information about the users currently on the machine, and their processes.
# w username
# w vivek

#4: uptime – Tell How Long The System Has Been Running

# uptime

#5: ps – Displays The Processes

Show Long Format Output

# ps -Al

Print All Process On The Server

# ps ax
# ps axu

Memmory commands cpu commands

Print Security Information

# ps -eo euser,ruser,suser,fuser,f,comm,label

Set Output In a User-Defined Format

ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm

ps -eopid,tt,user,fname,tmout,f,wchan

Display sorted process taking most CPU in descending order
# ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10