swapon(2) [redhat man page]

SWAPON(2)						     Linux Programmer's Manual							 SWAPON(2)

NAME

       swapon, swapoff - start/stop swapping to file/device

SYNOPSIS

       #include <unistd.h>
       #include <asm/page.h> /* to find PAGE_SIZE */
       #include <sys/swap.h>

       int swapon(const char *path, int swapflags);
       int swapoff(const char *path);

DESCRIPTION

       swapon  sets  the swap area to the file or block device specified by path.  swapoff stops swapping to the file or block device specified by
       path.

       swapon takes a swapflags argument.  If swapflags has the SWAP_FLAG_PREFER bit turned on, the new swap area will have a higher priority than
       default.  The priority is encoded as:

	   (prio << SWAP_FLAG_PRIO_SHIFT) & SWAP_FLAG_PRIO_MASK

       These functions may only be used by the super-user.

PRIORITY

       Each swap area has a priority, either high or low.  The default priority is low.  Within the low-priority areas, newer areas are even lower
       priority than older areas.

       All priorities set with swapflags are high-priority, higher than default.  They may have any  non-negative  value  chosen  by  the  caller.
       Higher numbers mean higher priority.

       Swap pages are allocated from areas in priority order, highest priority first.  For areas with different priorities, a higher-priority area
       is exhausted before using a lower-priority area.  If two or more areas have the same priority, and it is the  highest  priority	available,
       pages are allocated on a round-robin basis between them.

       As of Linux 1.3.6, the kernel usually follows these rules, but there are exceptions.

RETURN VALUE

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS

       Many other errors can occur if path is not valid.

       EPERM  The user is not the super-user, or more than MAX_SWAPFILES (defined to be 8 in Linux 1.3.6) are in use.

       EINVAL is returned if path exists, but is neither a regular path nor a block device.

       ENOENT is returned if path does not exist.

       ENOMEM is returned if there is insufficient memory to start swapping.

CONFORMING TO

       These  functions are Linux specific and should not be used in programs intended to be portable.	The second `swapflags' argument was intro-
       duced in Linux 1.3.2.

NOTES

       The partition or path must be prepared with mkswap(8).

SEE ALSO

       mkswap(8), swapon(8), swapoff(8)

Linux 1.3.6							    1995-07-22								 SWAPON(2)

Check Out this Related Man Page

SWAPON(8)						     Linux Programmer's Manual							 SWAPON(8)

NAME

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

SYNOPSIS

       /sbin/swapon [-h -V]
       /sbin/swapon -a [-v] [-e]
       /sbin/swapon [-v] [-p priority]	specialfile ...
       /sbin/swapon [-s]
       /sbin/swapoff [-h -V]
       /sbin/swapoff -a
       /sbin/swapoff specialfile ...

DESCRIPTION

       Swapon  is used to specify devices on which paging and swapping are to take place.  Calls to swapon normally occur in the system multi-user
       initialization file /etc/rc making all swap devices available, so that the paging and  swapping	activity  is  interleaved  across  several
       devices and files.

       Normally, the first form is used:

       -h     Provide help

       -V     Display version

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

       -a     All  devices marked as ``swap'' swap devices in /etc/fstab are made available. Devices that are already running as swap are silently
	      skipped.

       -e     When -a is used with swapon, -e makes swapon silently skip devices that do not exist.

       -p priority
	      Specify priority for swapon.  This option is only available if swapon was compiled under and is used under a 1.3.2 or later  kernel.
	      priority	is a value between 0 and 32767. 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.

       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 /etc/fstab).

NOTE

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

SEE ALSO

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

FILES

       /dev/hd??  standard paging devices
       /dev/sd??  standard (SCSI) paging devices
       /etc/fstab ascii filesystem description table

HISTORY

       The swapon command appeared in 4.0BSD.

Linux 1.x							 25 September 1995							 SWAPON(8)

Linux and UNIX Man Pages

swapon(2) [redhat man page]

Check Out this Related Man Page