NAME [Toc] [Back]
swapon - add swap space for interleaved paging/swapping
SYNOPSIS [Toc] [Back]
int swapon(const char *path, ...
/* [int min,
int priority */ );
Remarks [Toc] [Back]
The ANSI C ", ..." construct denotes a variable length argument list
whose optional and required members are given in the associated comment
DESCRIPTION [Toc] [Back]
The swapon() system call makes a block device or a directory named
path available to the system for paging and swapping.
priority indicates the order in which the swap space from the device
or file system is used. Space is taken from the lower-priority
swapon() can be used only by users who have appropriate privileges.
If path names a block device file
swapon() makes it available to the system at the specified priority
for allocation for paging and swapping.
In this form, swapon() takes only two arguments: the path to the block
device file, and the priority.
The device associated with path can be a device already known to the
system, defined at system configuration time, or it can be a
previously unspecified device.
If the device was already defined at system configuration time and
also has a start and/or size defined for that swap device, these
values are used.
Otherwise, if a filesystem exists on the device, swap is added
following the filesystem, or if no filesystem exists, the complete
device is used for swap.
See the appropriate system administrator's manual for information on
how the size of the swap area is calculated.
If path names a directory
swapon() makes the blocks on the file system rooted at path available
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for paging and swapping.
The min, limit, and reserve arguments are passed and used only if the
path argument names a directory.
min indicates the number of file system blocks to take from the file
system when swapon() is called.
limit indicates the maximum number of file system blocks the swap
system is allowed to take from the file system.
reserve indicates the number of file system blocks that are saved for
file system use only.
ERRORS [Toc] [Back]
If swapon() fails, errno is set to one of the following values.
[EACCES] A component of the path prefix denies search
[EALREADY] The device associated with path already has swap
[EBUSY] The device associated with path is already in use.
[EEXIST] The device associated with path was specified at
system configuration time to add swap at a
specified location, but that location is within an
existing file system on the device.
[EFAULT] The LIF header on the device associated with path
contains inconsistent directory data.
[EIO] Unable to read the device associated with path.
[ELOOP] Too many symbolic links were encountered in
translating the path name.
[ENAMETOOLONG] The length of the specified path name exceeds
PATH_MAX bytes, or the length of a component of
the path name exceeds NAME_MAX bytes while
_POSIX_NO_TRUNC is in effect.
[ENODEV] The device associated with path does not exist.
[ENOENT] The system-imposed limit on the number of swap
file entries has been reached.
[ENOSPC] There is is not enough available space on the
specified file system or device.
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[ENOSYS] The device associated with path was specified at
system configuration time to add swap following
the file system, but no file system was found.
[ENOTBLK] The path argument is not a block special file or
the root directory of a file system.
[ENOTDIR] A component of the path is not a directory.
[ENXIO] The device associated with path could not be
[EPERM] The effective user ID is not a user with
[EROFS] The device associated with path is read-only.
WARNINGS [Toc] [Back]
On systems running VxVM 3.5, the swap volumes to be configured for
system crash dumps should be created with the usage type as swap
during the creation of the swap volume. Not doing so will cause a
dump corruption. You could use the -U option of vxassist(1M) to do
No means is available to stop swapping to a device.
The system allocates no less than the amount specified in min.
However, to make the most efficient use of space, more than the amount
requested might be taken from the file system. The actual amount
taken will not exceed the number of file system blocks indicated in
Swapping to a file system is usually slower than swapping to a device.
Once file system blocks have been allocated for swap space, the file
system can not be unmounted unless the system is rebooted.
AUTHOR [Toc] [Back]
swapon() was developed by the University of California, Berkeley.
SEE ALSO [Toc] [Back]
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