|-c||Check the device (if it is a block device) for bad blocks before creating the swap area. If any are found, the count is printed.|
Force - 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.
Without this option mkswap will refuse to erase the first block on a device with a partition table or on whole disk (e.g. /dec/sda).
|-p PSZ||Specify the page size to use.|
|-L label||Specify a label, to allow swapon by label. (Only for new style swap areas.)|
Specify the swap space version. This option is deprecated and -v1 is
The kernel has not supported v0 swap space format since 2.5.22. The new version v1 is supported since 2.1.117.
Specify the uuid to use. The default is to generate UUIDs.
The maximum useful size of a swap area depends on the architecture and the kernel version. It is roughly 2GiB on i386, PPC, m68k, ARM, 1GiB on sparc, 512MiB on mips, 128GiB on alpha and 3TiB on sparc64. For kernels after 2.3.3 there is no such limitation.
Note that before 2.1.117 the kernel allocated one byte for each page, while it now allocates two bytes, so that taking a swap area of 2 GiB in use might require 2 MiB of kernel memory.
Presently, Linux allows 32 swap areas (this was 8 before Linux 2.4.10). The areas in use can be seen in the file /proc/swaps (since 2.1.25).
mkswap refuses areas smaller than 10 pages.
If you dont know the page size that your machine uses, you may be able to look it up with "cat /proc/cpuinfo" (or you may not - the contents of this file depend on architecture and kernel version).
To setup a swap file, it is necessary to create that file before initializing it with mkswap, e.g. using a command like
# dd if=/dev/zero of=swapfile bs=1024 count=65536
Note that a swap file must not contain any holes (so, using cp(1) to create the file is not acceptable).
The mkswap command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
|Linux||MKSWAP (8)||13 March 2009|