SYNOPSISIn unistd.h Ft int Fn swapon const char *special Ft int Fn swapoff const char *special
DESCRIPTIONThe Fn swapon system call makes the block device Fa 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 Fa special is calculated at the time the device is first made available for swapping.
The Fn swapoff system call disables paging and swapping on the given device. All associated swap metadata are deallocated, and the device is made available for other purposes.
RETURN VALUESIf an error has occurred, a value of -1 is returned and errno is set to indicate the error.
ERRORSBoth Fn swapon and Fn swapoff can fail if:
- Bq Er ENOTDIR
- A component of the path prefix is not a directory.
- Bq Er ENAMETOOLONG
- A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
- Bq Er ENOENT
- The named device does not exist.
- Bq Er EACCES
- Search permission is denied for a component of the path prefix.
- Bq Er ELOOP
- Too many symbolic links were encountered in translating the pathname.
- Bq Er EPERM
- The caller is not the super-user.
- Bq Er EFAULT
- The Fa special argument points outside the process's allocated address space.
Additionally, Fn swapon can fail for the following reasons:
- Bq Er ENOTBLK
- The Fa special argument is not a block device.
- Bq Er EBUSY
- The device specified by Fa special has already been made available for swapping
- Bq Er ENXIO
- The major device number of Fa special is out of range (this indicates no device driver exists for the associated hardware).
- Bq Er EIO
- An I/O error occurred while opening the swap device.
Lastly, Fn swapoff can fail if:
- Bq Er EINVAL
- The system is not currently swapping to Fa special .
- Bq Er ENOMEM
- Not enough virtual memory is available to safely disable paging and swapping to the given device.
HISTORYThe Fn swapon system call appeared in BSD 4.0 The Fn swapoff system call appeared in Fx 5.0 .