swapoff (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.

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)