SWAPON(3) BSD Library Functions Manual SWAPON(3)NAME
swapon -- add a swap device for interleaved paging/swapping
SYNOPSIS
#include <unistd.h>
int
swapon(const char *special);
DESCRIPTION
This interface is provided for compatibility only and has been obsoleted by swapctl(2).
swapon() makes the block device special available to the system for allocation for paging and swapping. The names of potentially available
devices are known to the system and defined at system configuration time. The size of the swap area on special is calculated at the time the
device is first made available for swapping.
RETURN VALUES
If an error has occurred, a value of -1 is returned and errno is set to indicate the error.
ERRORS
swapon() succeeds unless:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG]
A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
[ENOENT] The named device does not exist.
[EACCES] Search permission is denied for a component of the path prefix.
[ELOOP] Too many symbolic links were encountered in translating the pathname.
[EPERM] The caller is not the super-user.
[ENOTBLK] special is not a block device.
[EBUSY] The device specified by special has already been made available for swapping
[EINVAL] The device configured by special was not configured into the system as a swap device.
[ENXIO] The major device number of special is out of range (this indicates no device driver exists for the associated hardware).
[EIO] An I/O error occurred while opening the swap device.
[EFAULT] special points outside the process's allocated address space.
SEE ALSO swapctl(2), swapctl(8), swapon(8)HISTORY
The swapon() function call appeared in 4.0BSD and was removed NetBSD 1.3
BUGS
This call will be upgraded in future versions of the system.
BSD June 4, 1993 BSD
Check Out this Related Man Page
SWAPCTL(2) BSD System Calls Manual SWAPCTL(2)NAME
swapctl -- modify swap configuration
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
#include <sys/swap.h>
int
swapctl(int cmd, void *arg, int misc);
DESCRIPTION
The swapctl function is used to add and delete swap devices, and modify their configuration.
The cmd parameter specifies the operation to be performed. The arg and misc parameters have different meanings, depending on the cmd parame-
ter.
1. If cmd is SWAP_NSWAP, the current number of swap devices in the system is returned. The arg and misc parameters are ignored.
2. If cmd is SWAP_STATS, the current statistics for swap devices are returned in the arg parameter. No more than misc swap devices
are returned. The arg parameter should point to an array of at least misc struct swapent structures:
struct swapent {
dev_t se_dev; /* device id */
int se_flags; /* entry flags */
int se_nblks; /* total blocks */
int se_inuse; /* blocks in use */
int se_priority; /* priority */
char se_path[PATH_MAX+1]; /* path to entry */
};
The flags are defined as
SWF_INUSE in use: we have swapped here
SWF_ENABLE enabled: we can swap here
SWF_BUSY busy: I/O happening here
SWF_FAKE fake: still being built
3. If cmd is SWAP_ON, the arg parameter is used as a pathname of a file to enable swapping to. The misc parameter is used to set the
priority of this swap device.
4. If cmd is SWAP_OFF, the arg parameter is used as the pathname of a file to disable swapping from. The misc parameter is ignored.
5. If cmd is SWAP_CTL, the arg and misc parameters have the same function as for the SWAP_ON case, except that they change the prior-
ity of a currently enabled swap device.
6. If cmd is SWAP_DUMPDEV, the arg parameter is used as the pathname of a device to use as the dump device, should the system panic.
7. If cmd is SWAP_GETDUMPDEV, the arg parameter points to a dev_t, which is filled in by the current dump device.
When swapping is enabled on a block device, the first portion of the disk is left unused to prevent any disklabel present from being over-
written. This space is allocated from the swap device when the SWAP_ON command is used.
The priority of a swap device can be used to fill faster swap devices before slower ones. A priority of 0 is the highest, with larger num-
bers having lower priority. For a fuller discussion on swap priority, see the SWAP PRIORITY section in swapctl(8).
RETURN VALUES
If the cmd parameter is SWAP_NSWAP or SWAP_STATS, swapctl() returns the number of swap devices, if successful. The SWAP_NSWAP command is
always successful. Otherwise it returns 0 on success and -1 on failure, setting the global variable errno to indicate the error.
ERRORS
swapctl() succeeds unless:
[EACCES] Search permission is denied for a component of the path prefix.
[EBUSY] The device specified by arg has already been made available for swapping.
[EFAULT] arg points outside the process' allocated address space.
[EINVAL] The device configured by arg has no associated size, or the cmd was unknown.
[EIO] An I/O error occurred while opening the swap device.
[ELOOP] Too many symbolic links were encountered in translating the pathname.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
[ENOENT] The named device does not exist. For the SWAP_CTL command, the named device is not currently enabled for swapping.
[ENOTDIR] A component of the path prefix is not a directory.
[ENXIO] The major device number of arg is out of range (this indicates no device driver exists for the associated hardware); or
the block device specified by arg is not marked as a swap partition in the disklabel.
[EPERM] The caller is not the super-user.
SEE ALSO swapctl(8)HISTORY
The swapctl() function call appeared in NetBSD 1.3. The se_path member was added to struct swapent in NetBSD 1.4, when the header file was
also moved from <vm/vm_swap.h> to its current location in <sys/swap.h>.
AUTHORS
The current swap system was designed and implemented by Matthew Green <mrg@eterna.com.au>, with help from Paul Kranenburg <pk@NetBSD.org> and
Leo Weppelman <leo@NetBSD.org>, and insights from Jason R. Thorpe <thorpej@NetBSD.org>.
BSD May 17, 2010 BSD