-a | --all | | All devices marked as swap in /etc/fstab are made available, except for those with the noauto option Devices that are already being used as swap are silently skipped. |
-d | --discard[=policy] | | Enable swap discards, if the swap backing device supports the discard or trim operation. This may improve performance on some Solid State Devices, but often it does not. The option allows one to select between two available swap discard policies: --discard=once to perform a single-time discard operation for the whole swap area at swapon; or --discard=pages to asynchronously discard freed swap pages before they are available for reuse. If no policy is selected, the default behavior is to enable both discard types. The /etc/fstab mount options discard, discard=once, or discard=pages may also be used to enable discard flags. |
-e | --ifexists | | Silently skip devices that do not exist. The /etc/fstab mount option nofail may also be used to skip non-existing device. |
-f | --fixpgsz | | Reinitialize (exec mkswap) the swap space if its page size does not match that of the current running kernel. mkswap initializes the whole device and does not check for bad blocks. |
-L | | label | Use the partition that has the specified label. (For this, access to /proc/partitions is needed.) |
-o | --options | opts | Specify swap options by an fstab-compatible comma-separated string. For example swapon -o pri=1,discard=pages,nofail /dev/sda2 |
-p | --priority | priority | Specify the priority of the swap device. priority is a value between -1 and 32767. Higher numbers indicate higher priority. Add pri=value to the option field of /etc/fstab for use with swapon -a. When no priority is defined, it defaults to -1. |
-s | --summary | | Display swap usage summary by device. Equivalent to cat /proc/swaps. This output format is deprecated in favor of --show that provides better control on output data. (See also displaying swap space). |
| | --show | [=column…] | Display a definable table of swap areas. See the --help output for a list of available columns. |
| | --output-all | | Output all available columns. |
| | --noheadings | | Do not print headings when displaying --show output. |
| | --raw | | Display --show output without aligning table columns. |
| | --bytes | | Display swap size in bytes in --show output instead of in user-friendly units. |
-U | | uuid | Use the partition that has the specified UUID. |
-v | --verbose | | |
-h | --help | | |
-V | --version | | |