NAME<\/a> mkswap \u2212 set up a Linux swap area<\/p>\n mkswap<\/b> [options] device<\/i> [size<\/i>]<\/p>\n mkswap<\/b> sets up a Linux swap area on a device or in a file.<\/p>\n The device<\/i> argument will usually be a disk partition (something like \/dev\/sdb7<\/i>) but can also be a file. The Linux kernel does not look at partition IDs, but many installation scripts will assume that partitions of hex type 82 (LINUX_SWAP) are meant to be swap partitions. (Warning: Solaris also uses this type. Be careful not to kill your Solaris partitions.<\/b>)<\/p>\n The size<\/i> parameter is superfluous but retained for backwards compatibility. (It specifies the desired size of the swap area in 1024-byte blocks. mkswap<\/b> will use the entire partition or file if it is omitted. Specifying it is unwise \u2013 a typo may destroy your disk.)<\/p>\n After creating the swap area, you need the swapon<\/b> command to start using it. Usually swap areas are listed in \/etc\/fstab<\/i> so that they can be taken into use at boot time by a swapon \u2212a<\/b> command in some boot script.<\/p>\n The swap header does not touch the first block. A boot loader or disk label can be there, but it is not a recommended setup. The recommended setup is to use a separate partition for a Linux swap area.<\/p>\n mkswap<\/b>, like many others mkfs-like utils, erases the first partition block to make any previous filesystem invisible.<\/b><\/p>\n However, mkswap<\/b> refuses to erase the first block on a device with a disk label (SUN, BSD, …).<\/p>\n \u2212c<\/b>, \u2212\u2212check<\/b><\/p>\n Check the device (if it is a block device) for bad blocks before creating the swap area. If any bad blocks are found, the count is printed.<\/p>\n \u2212f<\/b>, \u2212\u2212force<\/b><\/p>\n Go ahead even if the command is stupid. This allows the creation of a swap area larger than the file or partition it resides on.<\/p>\n Also, without this option, mkswap<\/b> will refuse to erase the first block on a device with a partition table.<\/p>\n \u2212L<\/b>, \u2212\u2212label<\/b> label<\/i><\/p>\n Specify a label<\/i> for the device, to allow swapon<\/b> by label.<\/p>\n \u2212\u2212lock<\/b>[=mode<\/i>]<\/p>\n Use exclusive BSD lock for device or file it operates. The optional argument mode<\/i> can be yes<\/b>, no<\/b> (or 1 and 0) or nonblock<\/b>. If the mode<\/i> argument is omitted, it defaults to “yes”<\/b>. This option overwrites environment variable $LOCK_BLOCK_DEVICE<\/b>. The default is not to use any lock at all, but it\u2019s recommended to avoid collisions with udevd or other tools.<\/p>\n \u2212p<\/b>, \u2212\u2212pagesize<\/b> size<\/i><\/p>\n Specify the page size<\/i> (in bytes) to use. This option is usually unnecessary; mkswap<\/b> reads the size from the kernel.<\/p>\n \u2212U<\/b>, \u2212\u2212uuid<\/b> UUID<\/i><\/p>\n Specify the UUID<\/i> to use. The default is to generate a UUID.<\/p>\n \u2212v<\/b>, \u2212\u2212swapversion 1<\/b><\/p>\n Specify the swap-space version. (This option is currently pointless, as the old \u2212v 0<\/b> option has become obsolete and now only \u2212v 1<\/b> is supported. The kernel has not supported v0 swap-space format since 2.5.22 (June 2002). The new version v1 is supported since 2.1.117 (August 1998).)<\/p>\n \u2212h<\/b>, \u2212\u2212help<\/b><\/p>\n Display help text and exit.<\/p>\n \u2212V<\/b>, \u2212\u2212version<\/b><\/p>\n Display version information and exit.<\/p>\n LIBBLKID_DEBUG=all<\/p>\n enables libblkid debug output.<\/p>\n LOCK_BLOCK_DEVICE= use exclusive BSD lock. The mode is “1” or “0”. See \u2212\u2212lock<\/b> for more details.<\/p>\n The maximum useful size of a swap area depends on the architecture and the kernel version.<\/p>\n The maximum number of the pages that is possible to address by swap area header is 4294967295 (32-bit unsigned int). The remaining space on the swap device is ignored.<\/p>\n Presently, Linux allows 32 swap areas. The areas in use can be seen in the file \/proc\/swaps<\/i><\/p>\n mkswap<\/b> refuses areas smaller than 10 pages.<\/p>\n If you don\u2019t know the page size that your machine uses, you may be able to look it up with “cat \/proc\/cpuinfo” (or you may not \u2013 the contents of this file depend on architecture and kernel version).<\/p>\n To set up a swap file, it is necessary to create that file before initializing it with mkswap<\/b>, e.g. using a command like<\/p>\n # dd if=\/dev\/zero of=swapfile bs=1MiB count=$((8*1024))<\/p>\n to create 8GiB swapfile.<\/p>\n Please read notes from swapon<\/b>(8) about the swap file use restrictions<\/b> (holes, preallocation and copy-on-write issues).<\/p>\n
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