int hiwat );
Specifies the block special device to be made available. Specifies a flag. Only the MS_PREFER flag is currently supported, and it causes the specified path to be the preferred paging device. Specifies the low water mark. Specifies the high water mark.
The swapon() function makes a block special device available to the system for allocation of paging and swapping space. (The operating system does not currently support paging and swapping to a normal file. All swapping and pages areas must be block special devices.)
The lowat and hiwat parameters specify the low water and high water marks that the paging file will float between. If the low water mark is 0 (zero), then the file will not shrink after paging space is freed. If the high water mark is 0 (zero), then the file will grow without bounds. These parameters are not used for swapping devices. The size of the swap area on the block special device is calculated at the time the device is first made available for swapping.
The calling process must have superuser privilege to call the swapon() function.
Upon successful completion, the swapon() function returns a value of 0 (zero). If an error has occurred, -1 is returned and errno is set to indicate the error.
If the swapon() function fails, errno may be set to one of the following values: A component of the path prefix is not a directory. The pathname contains a character with the high-order bit set, the device was not specified, the device configured by the path parameter was not configured into the system as a swap device, or the device does not allow paging. A component of a pathname exceeded NAME_MAX characters, or an entire pathname exceeded PATH_MAX characters. The named device does not exist. Search permission is denied for a component of the path prefix. Too many symbolic links were encountered in translating the pathname. The caller does not have appropriate privilege. The device specified by the path parameter has already been made available for swapping. The major device number of the path parameter is out of range (this indicates no device driver exists for the associated hardware). An I/O error occurred while opening the swap device. The path parameter points outside the process' allocated address space. An attempt was made to activate a paging file on a read-only file system.
Commands: swapon(8), config(8) delim off