| .\" Copyright 1992, 1993 Rickard E. Faith (faith@cs.unc.edu) |
| .\" May be distributed under the GNU General Public License |
| .\" Modified with suggestions from Linus, Mon Feb 1 21:40:49 1993 |
| .\" Modified with patches from Kai, Wed Jun 22 21:54:56 1994 |
| .\" Patches from jaggy@purplet.demon.co.uk (Mike Jagdis), Wed Feb 8 1995 |
| .\" Added comments from Nick Holloway, Sat Feb 11 1995, faith@cs.unc.edu |
| .\" " |
| .TH MKSWAP 8 "8 February 1995" "Linux 1.0" "Linux Programmer's Manual" |
| .SH NAME |
| mkswap \- set up a Linux swap device |
| .SH SYNOPSIS |
| .B "mkswap [ \-c ]" |
| .IB device " [" size-in-blocks "]" |
| .SH DESCRIPTION |
| .B mkswap |
| sets up a Linux swap area on a device (usually a disk partition). |
| |
| The |
| .I device |
| is usually of the following form: |
| |
| .nf |
| .RS |
| /dev/hda[1-8] |
| /dev/hdb[1-8] |
| /dev/sda[1-8] |
| /dev/sdb[1-8] |
| .RE |
| .fi |
| |
| The |
| .I size-in-blocks |
| parameter is the desired size of the file system, in blocks. This |
| information is determined automatically by mkswap if it is omitted. Block |
| counts are rounded down to pages of 4 kB each. Only block counts equal to |
| or greater than 40 and equal to or less than 131072 are allowed. Block |
| counts greater than 130752 are (silently) rounded down to 130752. |
| |
| As Nick Holloway explains, the actual maximum for each swap file/partition |
| is: |
| .RS |
| (4096 - 10) * 8 * 4096 = 133890048 bytes = 130752 blocks = 127.6875 Mb |
| .RE |
| This is because a single page is used to hold the swap bitmap at the |
| start of the partition, where each bit is a single 4K page. The reason |
| for the -10, is that the signature is "SWAP-SPACE" -- 10 characters. |
| |
| .B mkswap |
| can also set up swap files, although the file has to be created first. A |
| sequence of commands similar to the following is reasonable for this |
| purpose: |
| |
| .nf |
| .RS |
| # dd if=/dev/zero of=swapfile bs=1024 count=8192 |
| # mkswap swapfile 8192 |
| # sync |
| # swapon swapfile |
| .RE |
| .fi |
| |
| Note that the regular file has to be created before running |
| .B mkswap |
| on the file, and that the file must not contain any holes (so, using |
| .BR cp (1) |
| to create the file is not acceptable). |
| |
| .SH OPTIONS |
| .TP |
| .B \-c |
| Check the device for bad blocks before creating the file system. If any |
| are found, the count is printed. This option is meant to be used for swap |
| partitions |
| .BR only , |
| and should |
| .B not |
| be used for regular files! To make sure that regular files do not contain |
| bad blocks, the partition that contains the regular file should have been |
| created with |
| .BR "mkfs -c" . |
| .SH "SEE ALSO" |
| .BR fsck (8), |
| .BR mkfs (8), |
| .BR fdisk (8) |
| .SH AUTHOR |
| Linus Torvalds (torvalds@cs.helsinki.fi) |
