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How To Check Linux Swap Space Is On Which Disk Partitions?

The free command tells how much swap space is on a Linux system, but it doesn’t tell where it is. When this question pops up in my mind, I check the /etc/fstab file and the result is mostly accurate except on one server that I’ve just reinstalled.

The suspicious fstab file content seems to hint me that the swap space is on sdk2 disk partition, which I know is definitely not:
LABEL=SWAP-sdk2   swap   swap   defaults   0 0

What’s the evidence? Well, the fdisk -l /dev/sdk shows there is no swap partition. Indeed, the only swap partition is on /dev/sda (first SCSI hard disk) and the partition size does match with the swap space reported by free command:
fdisk -l /dev/sda

Disk /dev/sda: 299.4 GB, 299439751168 bytes
255 heads, 63 sectors/track, 36404 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot Start  End   Blocks  Id System
/dev/sda1   *      1   13   104391  83 Linux
/dev/sda2         14 2060 16442527+ 82 Linux swap

free -m
             total used  free shared buffers cached
Mem:         16043  842 15201      0     126    372
-/+ buffers/cache:  343 15700
Swap:        16057    0 16057

To get further confirmation, I examine /proc/swaps:
cat /proc/swaps
Filename   Type       Size     Used  Priority
/dev/sda2  partition  16442516    0        -1

Conclusion: To find out which disk partition is used for Linux swap space, try to check /proc/swaps file. In additional, confirm the size reported by “fdisk -l” and “free” command is matching.

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