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SWAPON(8)	       DragonFly System Manager's Manual	     SWAPON(8)

NAME

swapon, swapoff, swapctl -- specify devices for paging and swapping

SYNOPSIS

swapon -aceiq | file ... swapoff -aq | file ... swapctl [-AeghklmsU] [-a file ... | -d file ...]

DESCRIPTION

The swapon, swapoff and swapctl utilities are used to control swap devices in the system. At boot time all swap entries in /etc/fstab are added automatically when the system goes multi-user. Swap devices use a fixed interleave; the maximum number of devices is specified by the ker- nel configuration option NSWAPDEV, which is typically set to 4. There is no priority mechanism. The swapon utility adds the specified swap devices to the system. If the -a option is used, all swap devices in /etc/fstab will be added. The following options are supported: ``noauto'' The device is ignored and will not be added or removed with this option. ``crypt'' Swap will be encrpted with a random key using a /dev/mapper name of swap-<device> , for example 'swap-da0s1b'. This will also load the dm_target_crypt module if necessary. ``trim'' Swap will be TRIMed if the device supports it, otherwise this option will be ignored. If the -q option is used informational messages will not be written to standard output when a swap device is added. If the -c option is used, the device will be encrypted with a random key. If the -e option is used, the device will be trimmed if it supports trim and the trim_enabled sysctl is on. The -i option asks user confirmation before adding a swap device. The swapoff utility removes the specified swap devices from the system. If the -a option is used, all swap devices in /etc/fstab will be removed, unless their ``noauto'' option is also set. If the -c option is used the device is mapped to the appropriate crypto device and the crypto device is removed as well. If this option is specified in swapon then it should also be specified in swapoff. If the -q option is used informational messages will not be written to standard output when a swap device is removed. Note that swapoff will fail and refuse to remove a swap device if there is insufficient VM (memory + remaining swap devices) to run the system. The swapoff utility must move swapped pages out of the device being removed which could lead to high system loads for a period of time, depending on how much data has been swapped out to that device. The swapctl utility exists primarily for those familiar with other BSDs and may be used to add, remove, or list swap devices. Note that the -a option is used differently in swapctl and indicates that a specific list of devices should be added. The -d option indicates that a specific list should be removed. The -A and -U options to swapctl operate on all swap entries in /etc/fstab which do not have their ``noauto'' option set. Swap information can be generated using the swapinfo(8) utility, pstat -s, or swapctl -l. The swapctl utility has the following options for listing swap: -h Output values in human-readable form. -g Output values in gigabytes. -k Output values in kilobytes. -m Output values in megabytes. -l List the devices making up system swap. -s Print a summary line for system swap. infinityThe swap is or should be crypted. -e Attempts to Trim the device if -[Aa] is used. -i Asks user confirmation when -a is used. -q Less noisy output. The BLOCKSIZE environment variable is used if not specifically overridden. 1K blocks are used by default.

FILES

/dev/{ad,da}?s?b standard paging devices /dev/vn?s?b vnode disk paging device /etc/fstab ASCII filesystem description table /etc/vntab ASCII vnode file table

DIAGNOSTICS

These utilities may fail for the reasons described in swapon(2).

SEE ALSO

swapon(2), fstab(5), init(8), pstat(8), rc(8), vnconfig(8)

HISTORY

The swapon utility appeared in 4.0BSD. The swapoff and swapctl utilities appeared in FreeBSD 5.1 and were later ported to DragonFly 2.7. DragonFly 5.3 September 7, 2010 DragonFly 5.3 SWAPON(2) DragonFly System Calls Manual SWAPON(2)

NAME

swapon, swapoff -- control devices for interleaved paging/swapping

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <unistd.h> int swapon(const char *special); int swapoff(const char *special);

DESCRIPTION

The swapon() system call 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 configu- ration time. The size of the swap area on special is calculated at the time the device is first made available for swapping. The 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 VALUES

If an error has occurred, a value of -1 is returned and errno is set to indicate the error.

ERRORS

Both swapon() and swapoff() can fail if: [ENOTDIR] A component of the path prefix is not a directory. [ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 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 translat- ing the pathname. [EPERM] The caller is not the super-user. [EFAULT] The special argument points outside the process's allocated address space. Additionally, swapon() can fail for the following reasons: [EINVAL] The system has reached the boot-time limit on the num- ber of swap devices, vm.nswapdev. [ENOTBLK] The special argument is not a block device. [EBUSY] The device specified by special has already been made available for swapping [ENXIO] The major device number of special is out of range (this indicates no device driver exists for the asso- ciated hardware). [EIO] An I/O error occurred while opening the swap device. Lastly, swapoff() can fail if: [EINVAL] The system is not currently swapping to special. [ENOMEM] Not enough virtual memory is available to safely dis- able paging and swapping to the given device.

SEE ALSO

config(8), swapon(8), sysctl(8)

HISTORY

The swapon() system call appeared in 4.0BSD. The swapoff() system call appeared in FreeBSD 5.0 and was later ported to DragonFly 2.7. DragonFly 5.3 September 7, 2010 DragonFly 5.3

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