Free command

From RZWiki

A CLI command line program available on most Linux platforms; used to display physical and swap memory information and usage statistics.

Usage Syntax

free [options]

Common options include;

-b - display information in Bytes
-k - display information in kiloBytes
-m - display information in MegaBytes
-g - display information in GigaBytes
-l - display information about low and high memory usage
-c number - display information the specified number of times and then exit, must be used with the -s option
-s number - repeat, pausing the specified number of seconds, continues indefinately unless the -c option has been used

Usage Examples

free - display summary physical and swap memory usage information

free -mc 2 -s 2 - display summary physical and swap memory usage information, in megabytes, three times with a two second interval

Usage Notes

The information displayed is actually stored in file: /proc/meminfo

Take a look at our Improve Ubuntu Linux Performance article for information on how to increase available memory and reduce or eliminate the use of slow swap memory.

Linux Usage Notes

With most Linux or Unix commands;

Non root users may need to prefix commands with the sudo command, for example: sudo chmod 644 *
Brief help can be displayed using the -h or --help parameter, for example: chmod --help
A full command manual can be displayed using the man command followed by the command name, for example: man chmod
Sometimes 'info' pages are used instead of or to provide more information than man pages; for example: info chmod
Version information can normally be display using the -v, -V or --version parameter, for example: chmod --version. However, this paramater is also frequently used to display verbose output.

noinclude/noinclude

Typical Output

noinclude/noinclude

             total       used       free     shared    buffers     cached
Mem:           371        361         10          0        103         82
-/+ buffers/cache:        175        196
Swap:         3014         78       2935