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How to check Memory Usage in Linux via Command Line (Ubuntu)

Most of our readers are really interested in Linux and kept on requesting me to post articles on basic of Linux for newbie. We do understand the problem of newbie and we here at Techie Inspire always tries to be simple and informative. Generally, when newbies use Linux for first time, they start wondering about how to check memory usage, like we do in windows using the task manager. This guide will show you how to check memory usage in Linux using the command line.

how to check memory usage in linux


There are three commands which will do the task

  1. Free
  2. Vmstat
  3. Top


Command Line Command:


  • Free

Free displays the total amount of free and used physical memory and swap space in the system, as well as the buffers and cache consumed by the kernel.

Syntax of free

free -[options]

Type below command in command line, It will display a table of six column and three rows of data, all expressed in kilobytes.


Type below command in command line, It will display data in megabyte (MB)

free -m

Free linux command

Other options that you can try,

-b – Displays output in bytes

-k – Display output in Kilobytes (KB), This is the default.

-g – Display output in Kilobytes (GB).

-l – Display low vs. high memory usage.

-t – Display total summary for physical memory + swap space.

-s n, -repeat=n

Repeat, pausing every n seconds in-between.

-V – version

Display version information and exit.


  • vmstat

vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity. This could also help in instant report on memory usage.

Syntax of vmstat

vmstat [-n] [delay [ count]]

Type below command in command line, It will display vmstat with 5 second delay.

vmstat 5

Type below command in command line, It will display vmstat with 5 second delay repeat up to 10 times

vmstat 5 10

vmstat linux command

Other options that you can try,

-n switch causes the header to be displayed only once rather than


-s switch displays a table of various event counters and memory


-V switch results in displaying version information.



  • Top

“Top” command display cpu processes activity in real time, It shows the top most cpu processes which are running on your system. It also helps to sort the task by memory usage, Cpu usage and real-time basis. Besides of displaying process information, it furthermore displays free memory of physical as well as swap.

Syntax of top

top -[options]

Type below command in command line, It will display real-time CPU processes


top linux command

Other options that you can try,

-d         Specifies the delay between screen updates. You can change this with the s interactive command.

-p         Monitor only processes with given process id. This flag can be given up to twenty times. This option is neither available interactively nor can it be put into the configuration file.

-q         This causes top to refresh without any delay. If the caller has superuser privileges, top runs with the highest possible priority.

-C         Display total CPU states instead of individual CPUs. This option only affects SMP systems.


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About Roshan Karkera

Roshan Karkera a.k.a. k.roshan. Blogger by passion and software engineer by profession. He believes in sharing knowledge, which made him to start his own blog. He is very much keen & passionate about new technology & Science. If you'd like to connect with him, follow at Google plus or Twitter.


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  7. I would suggest replacing top with htop and vmstat with dstat …

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