How can I check if swap is active, and which swap devices are set up, on the command line?
in linux, you can use
cat /proc/meminfoto see total swap, and free swap (all linux)
cat /proc/swapsto see which swap devices are being used (all linux)
swapon -sto see swap devices and sizes (where swapon is installed)
vmstatfor current virtual memory statistics
in Mac OS X, you can use
vm_statto 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 -lto see swap devices/files, and their sizes
swap -sto see total swap size, used & free
vmstatto 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.
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
swap is not active, it doesn't show anything.
man swap says:
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.
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.
With Linux you can use the
top command to see if the swap is active or not, in which you can see something like
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.