How can I check if swap is active from the command line?

Question

How can I check if swap is active, and which swap devices are set up, on the command line?

score 267 · Accepted Answer · edited May 28 '13 at 07:40

267

in linux, you can use

cat /proc/meminfo to see total swap, and free swap (all linux)
cat /proc/swaps to see which swap devices are being used (all linux)
swapon -s to see swap devices and sizes (where swapon is installed)
vmstat for current virtual memory statistics

in Mac OS X, you can use

vm_stat to see information about virtual memory (swap)
ls -lh /private/var/vm/swapfile* to see how many swap files are being used.

in Solaris, you can use

swap -l to see swap devices/files, and their sizes
swap -s to see total swap size, used & free
vmstat to see virtual memory statistics

On some systems, "virtual memory" refers only to disk-backed memory devices, and on other systems, like Solaris, Virtual Memory can refer to any user process address space, including tmpfs filesystems (like /tmp) and shared memory space.

edited May 28 '13 at 07:40

peterph

30,838

answered Oct 22 '11 at 04:40

Tim Kennedy

19,697

22

Also, free should tell you how much swap is available to your system. – May 28 '13 at 10:31
2

cat /proc/meminfo should be cat /proc/meminfo | grep Swap – Binar Web Jun 11 '19 at 04:09
use free -h for human readable sizes. – red-o-alf Apr 23 '23 at 17:56
1

The swapon -s (--summary) seems to be deprecated at least in util-linux 2.37.2. The swapon --show shows similar information. – Niko Fohr Nov 29 '23 at 20:55

Ciro Santilli OurBigBook.com · Answer 2 · 2021-06-08T09:41:34.747

swapon --show

This is a bit better than swapon -s as it provides human friendly size units. E.g. if swap is active you could see:

NAME      TYPE      SIZE   USED PRIO
/dev/dm-1 partition 7.5G 563.8M   -2

If swap is not active, it doesn't show anything.

man swap says:

-s, --summary

Display swap usage summary by device. Equivalent to "cat /proc/swaps". This output format is DEPRECATED in favour of --show that provides better control on output data.

--show[=column...]

Display a definable table of swap areas. See the --help > output for a list of available columns.

Tested in Ubuntu 18.04, util-linux 2.31.1.

score 34 · Answer 3 · answered Oct 22 '11 at 04:26

34

Try swapon -s for a list of current swap devices and other relevant information.

answered Oct 22 '11 at 04:26

jw013

51,212

score 3 · Answer 4 · answered May 18 '16 at 01:29

With Linux you can use the top command to see if the swap is active or not, in which you can see something like kswapd0. The top command provides a dynamic real-time view of a running system, thus you should see the swap there.

If you don't see it there, it's more then likely it isn't working. to restart it or enable it, you can use this command: sudo swapon --all --verbose (source)

Then by running the topcommand again you should see it.

How can I check if swap is active from the command line?

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