Thursday, 15 January 2009

Creating and formatting swap partitions

You can have
several swap partitions. [Older Linux kernels limit the size of each swap
partition to up to approximately 124 MB, but the linux kernels 2.2.x up
do not have this restriction.] Here are the steps to create and enable
a swap partition:

- Create the partition of the proper size using fdisk (partition
type 82, "Linux swap").

- Format the partition checking for bad blocks, for example:

mkswap -c /dev/hda4

You have to substitute /dev/hda4 with your partition name. Since I did
not specify the partition size, it will be automatically detected.

- Enable the swap, for example:

swapon /dev/hda4

To have the swap enabled automatically at bootup, you have to include
the appropriate entry into the file /etc/fstab, for example:

/dev/hda4 swap swap defaults 0 0

If you ever need to disable the swap, you can do it with (as root):

swapoff /dev/hda4

Swap partitions

Swap is an extension of the physical memory of the computer. Most likely, you
created a swap partition during the initial RedHat setup. You can
verify the amount of swap space available on your system using:

cat /proc/meminfo

The general recommendation is that one should have: at least 4 MB
swap space, at least 32 MB total (physical+swap) memory for a system running
command-line-only, at least 64 MB of total (physical+swap) memory for
a system running X-windows, and swap space at least 1.5 times the amount
of the physical memory on the system.

If this is too complicated, you might want to have a swap twice as large
as your physical (silicon) memory, but not less than 64 MB.

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