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How to check memory usage on CentOS Server

How to check memory usage on CentOS Server

Linux operating system comes with many commands to check memory usage. The “free” command usually displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel. The “top” command provides a dynamic real-time view of a running system.

memory usage

The top command can display system summary information as well as a list of the process currently being managed by the Linux kernel.

In this article we will see the ways to check the memory usage on CentOS.

Checking memory usage on CentOS

Follow the below command to check memory usage on Linux machine.

/proc/meminfo

You can check memory usage is to read the /proc/meminfo file. The same file is used to know the free and other utilities report of free and used memory (both physical and swap) on the system.

# cat /proc/meminfo
or
# egrep --color 'Mem|Cache|Swap' /proc/meminfo

 

You will get some output like below:

MemTotal:   7996284 kB
MemFree:    5415608 kB
Cached:       92416 kB
SwapCached:   35924 kB
SwapTotal:  8187836 kB
SwapFree:   8059332 kB

free Command

You can check the total free and used physical and swap memory as well as the buffer used using free command.

# free -m

You will get some output like below:

             total       used       free     shared    buffers     cached
Mem:          1006        317        689          0         36        190
-/+ buffers/cache:         90        916
Swap:         2015          0       2015

where Command

The whereis command lets users locate binary, source, and manual page files for a command. Following is its syntax:

Whereis [options]
-b,-k,-m,-g: show output in bytes, KB, MB, or GB
–l: show detailed low and high memory statistics
–o: use old format (no -/+buffers/cache line)
–t: display total for RAM + swap
–s: update every [delay] seconds
–c: update [count] times

vmstat command

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

# vmstat

You will some output like below:

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0      0 701072  38236 198804    0    0    18    23   88   97  1  3 96  1  0

The vmstat command with the s option, lays out the memory usage statistics much like the proc command.

# vmstat -s

You will some output like below:

7996284    total memory
3028732    used memory
2587708    active memory
253600     inactive memory
4967552    free memory
32212      buffer memory
97732      swap cache
8187836    total swap
127572     used swap
8060264    free swap
2629730    non-nice user cpu ticks
890        nice user cpu ticks
335618     system cpu ticks
80671997   idle cpu ticks
14269700   IO-wait cpu ticks
8          IRQ cpu ticks
12963      softirq cpu ticks
0          stolen cpu ticks
320259348  pages paged in
496267028  pages paged out
40038      pages swapped in
85154      pages swapped out
151875583  interrupts
278983792  CPU context switches
1438090342 boot time
300883     forks

atop command

The program atop is an interactive monitor to view the load on a Linux system. This program can display the amount of used and free memory, i.e. cpu, memory, disk and network.

# atop

htop command

It is similar to top, also allows you to see all the processes running on the system, with their full command lines.

#htop

top command

The Linux top command is used to show all the running processes within your Linux environment.

 #top

or

 # top c

Hope, this article helps you. Please share your valuable feedback to improve us.

To monitor the real time resource usage in Cloud linux: Click here

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