Provided by: loop-aes-utils_2.16.2-2ubuntu1_amd64 bug


       swapon, swapoff - enable/disable devices and files for paging and swapping


       Get info:
            swapon -s [-h] [-V]

            swapon [-f] [-p priority] [-v] specialfile...
            swapoff [-v] specialfile...

       Enable/disable all:
            swapon -a [-e] [-f] [-v]
            swapoff -a [-v]


       swapon is used to specify devices on which paging and swapping are to take place.

       The  device  or  file used is given by the specialfile parameter. It may be of the form -L
       label or -U uuid to indicate a device by label or uuid.

       Calls to swapon normally occur  in  the  system  boot  scripts  making  all  swap  devices
       available,  so that the paging and swapping activity is interleaved across several devices
       and files.

       swapoff disables swapping on the specified devices and files.  When the -a flag is  given,
       swapping  is  disabled  on  all  known  swap devices and files (as found in /proc/swaps or

       If loop=/dev/loop?  and encryption=AES128 options are present in /etc/fstab then swapon -a
       will  set up loop devices using random keys, run mkswap on them, and enable encrypted swap
       on specified loop devices. Encrypted loop devices are set up with page size offset so that
       unencrypted  swap  signatures  on  first page of swap devices are not touched.  swapoff -a
       will tear down such loop devices.

       -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.

       -e, --ifexists
              Silently skip devices that do not exist.

       -f, --fixpgsz
              Reinitialize (exec /sbin/mkswap) the swap space if its page  size  does  not  match
              that of the the current running kernel.  mkswap(2) initializes the whole device and
              does not check for bad blocks.

       -h, --help
              Provide help.

       -L label
              Use  the  partition  that  has  the  specified  label.   (For   this,   access   to
              /proc/partitions is needed.)

       -p, --priority priprity
              Specify  the priority of the swap device.  priority is a value between 0 and 32767.
              Higher numbers indicate higher priority. See swapon(2) for a  full  description  of
              swap  priorities.  Add  pri=value  to  the  option field of /etc/fstab for use with
              swapon -a.

       -s, --summary
              Display swap usage  summary  by  device.  Equivalent  to  "cat  /proc/swaps".   Not
              available before Linux 2.1.25.

       -U uuid
              Use the partition that has the specified uuid.

       -v, --verbose
              Be verbose.

       -V, --version
              Display version.


       You should not use swapon on a file with holes.  Swap over NFS may not work.

       swapon  automatically  detects and rewrites swap space signature with old software suspend
       data (e.g S1SUSPEND, S2SUSPEND, ...). The problem is that if we don't do it, then  we  get
       data corruption the next time an attempt at unsuspending is made.


       swapon(2), swapoff(2), fstab(5), init(8), mkswap(8), rc(8), mount(8)


       /dev/sd??  standard paging devices
       /etc/fstab ascii filesystem description table


       The swapon command appeared in 4.0BSD.


       The   swapon  command  is  part  of  the  util-linux-ng  package  and  is  available  from