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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_PRE-
       FER 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	prior-
       ity 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)

NAME | SYNOPSIS | DESCRIPTION | PRIORITY | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO

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