.\" Hey Emacs! This file is -*- nroff -*- source. .\" .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 .\" .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" .\" Modified by Michael Haardt .\" Modified Sat Jul 24 11:47:53 1993 by Rik Faith .\" Modified 22 July 1995 by Michael Chastain : .\" Added 'swapflags' argument. .\" Added historical remark, aeb, 950723. .\" Modified Tue Oct 22 22:23:50 1996 by Eric S. Raymond .\" .TH SWAPON 2 "22 July 1995" "Linux 1.3.6" "Linux Programmer's Manual" .SH NAME swapon, swapoff \- start/stop swapping to file/device .SH SYNOPSIS .B #include .br .B #include .sp .BI "int swapon(const char *" path ", int " swapflags ); .br .BI "int swapoff(const char *" path ); .SH DESCRIPTION .B swapon sets the swap area to the file or block device specified by .IR path . .B swapoff stops swapping to the file or block device specified by .IR path . .PP .B swapon takes a .I swapflags argument. If .I swapflags has the .I SWAP_FLAG_PREFER bit turned on, the new swap area will have a higher priority than default. The priority is encoded as: .br .sp .I " (prio << SWAP_FLAG_PRIO_SHIFT) & SWAP_FLAG_PRIO_MASK" .br .PP These functions may only be used by the super-user. .SH "PRIORITY" Each swap area has a priority, either high or low. The default priority is low. Within the low-priority areas, newer areas are even lower priority than older areas. .PP All priorities set with .I swapflags are high-priority, higher than default. They may have any non-negative value chosen by the caller. Higher numbers mean higher priority. .PP 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. .PP As of Linux 1.3.6, the kernel usually follows these rules, but there are exceptions. .SH "RETURN VALUE" On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS Many other errors can occur if .I path is not valid. .TP 0.8i .B EPERM The user is not the super-user, or more than .B MAX_SWAPFILES (defined to be 8 in Linux 1.3.6) are in use. .TP .B EINVAL is returned if .I path exists, but is neither a regular path nor a block device. .TP .B ENOENT is returned if .I path does not exist. .TP .B ENOMEM is returned if there is insufficient memory to start swapping. .SH "CONFORMING TO" These functions are Linux specific and should not be used in programs intended to be portable. The second `swapflags' argument was introduced in Linux 1.3.2. .SH NOTES The partition or path must be prepared with .BR mkswap (8). .SH "SEE ALSO" .BR mkswap "(8), " swapon "(8), " swapoff (8)