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dynamic_pager(8) [osx man page]

dynamic_pager(8)					    BSD System Manager's Manual 					  dynamic_pager(8)

dynamic_pager -- external storage manager for dynamic pager SYNOPSIS
dynamic_pager [-F filename] [-S filesize] [-H high-water-trigger] [-L low-water-trigger] [-P priority] DESCRIPTION
The dynamic_pager daemon manages a pool of external swap files which the kernel uses to support demand paging. This pool is expanded with new swap files as load on the system increases. It is contracted when the swapping resources are no longer needed. The dynamic_pager daemon also provides a notification service for those applications which wish to receive notices when the external paging pool expands or contracts. OPTIONS
-F The base name of the filename to use for the external paging files. By default this is /private/var/vm/swapfile. -H If there are less than high-water-trigger bytes free in the external paging files, the kernel will signal dynamic_pager to add a new external paging file. -L If there are more than low-water-trigger bytes free in the external paging files, the kernel will coalese in-use pages and signal dynamic_pager to discard an external paging file. Low-water-trigger must be greater than high-water-trigger + filesize. -P This option is currently unimplemented. -S The fixed filesize [in bytes] to use for the paging files. By default dynamic_pager uses variable sized paging files, using larger sized files as paging demands increase. The -S, -H and -L options disable that default and cause dynamic_pager to use a series of fixed sized external paging files. FILES
/private/var/vm/swapfile* Default external paging files. /Library/Preferences/ Configuration file. XML PROPERTY LIST KEYS
The following keys can be specified in the configuration file. Please see plist(5) for more information about property list files. UseEncryptedSwap <boolean> This optional key activates encrypted swap (aka Secure VM), so that all data is encrypted before being written to a swap file. The default is on for portable computers and off for other computers. Mac OS X July 8, 2003 Mac OS X

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SWAPON(8)						     Linux Programmer's Manual							 SWAPON(8)

swapon, swapoff - enable/disable devices and files for paging and swapping SYNOPSIS
Get info: swapon -s [-h] [-V] Enable/disable: swapon [-f] [-p priority] [-v] specialfile... swapoff [-v] specialfile... Enable/disable all: swapon -a [-e] [-f] [-v] swapoff -a [-v] DESCRIPTION
swapon is used to specify devices on which paging and swapping are to take place. The device or file used is given by the specialfile parameter. It may be of the form -L label or -U uuid to indicate a device by label or uuid. Calls to swapon normally occur in the system boot scripts making all swap devices available, so that the paging and swapping activity is interleaved across several devices and files. swapoff disables swapping on the specified devices and files. When the -a flag is given, swapping is disabled on all known swap devices and files (as found in /proc/swaps or /etc/fstab). -a, --all All devices marked as ``swap'' in /etc/fstab are made available, except for those with the ``noauto'' option. Devices that are already being used as swap are silently skipped. -e, --ifexists Silently skip devices that do not exist. -f, --fixpgsz Reinitialize (exec /sbin/mkswap) the swap space if its page size does not match that of the the current running kernel. mkswap(2) initializes the whole device and does not check for bad blocks. -h, --help Provide help. -L label Use the partition that has the specified label. (For this, access to /proc/partitions is needed.) -p, --priority priority Specify the priority of the swap device. priority is a value between 0 and 32767. Higher numbers indicate higher priority. See swapon(2) for a full description of swap priorities. Add pri=value to the option field of /etc/fstab for use with swapon -a. -s, --summary Display swap usage summary by device. Equivalent to "cat /proc/swaps". Not available before Linux 2.1.25. -U uuid Use the partition that has the specified uuid. -v, --verbose Be verbose. -V, --version Display version. NOTES
You should not use swapon on a file with holes. Swap over NFS may not work. swapon automatically detects and rewrites swap space signature with old software suspend data (e.g S1SUSPEND, S2SUSPEND, ...). The problem is that if we don't do it, then we get data corruption the next time an attempt at unsuspending is made. swapon may not work correctly when using a swap file with some versions of btrfs. This is due to the swap file implementation in the ker- nel expecting to be able to write to the file directly, without the assistance of the file system. Since btrfs is a copy-on-write file system, the file location may not be static and corruption can result. Btrfs actively disallows the use of files on its file systems by refusing to map the file. This can be seen in the system log as "swapon: swapfile has holes." One possible workaround is to map the file to a loopback device. This will allow the file system to determine the mapping properly but may come with a performance impact. SEE ALSO
swapon(2), swapoff(2), fstab(5), init(8), mkswap(8), rc(8), mount(8) FILES
/dev/sd?? standard paging devices /etc/fstab ascii filesystem description table HISTORY
The swapon command appeared in 4.0BSD. AVAILABILITY
The swapon command is part of the util-linux-ng package and is available from Linux 1.x 25 September 1995 SWAPON(8)
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