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2.2. Adding Swap Space Sometimes it is necessary to add more swap space after installation. For
example, you may upgrade the amount of RAM in your system from 64 MB to
128 MB, but there is only 128 MB of swap space. It might be advantageous
to increase the amount of swap space to 256 MB if you perform
memory-intense operations or run applications that require a large
amount of memory.
You have two options: add a swap partition or add a swap file. It is
recommended that you add a swap partition, but that can be difficult if
you do not have any free space available.
To add a swap partition (assuming /dev/hdb2 is the
swap partition you want to add):
The hard drive can not be in use (partitions can not be mounted,
and swap space can not be enabled). The partition table should not be
modified while in use because the kernel may not properly recognize
the changes. Data could be overwitten by writing to the wrong
partition because the partition table and partitions mounted do not
match. The easiest way to achieve this is to boot your system in
rescue mode. Refer to Chapter 11 Basic System Recovery for instructions
on booting into rescue mode. When prompted to mount the file system,
select Skip. Alternately, if the drive does not contain any partitions in
use, you can unmount them and turn off all the swap space on the hard
drive with the swapoff command. Create the swap partition using parted:
At a shell prompt as root, type the command parted
/dev/hdb, where
/dev/hdb is the device name for the
hard drive with free space. At the (parted) prompt, type
print to view the existing partitions and
the amount of free space. The start and end values are in
megabytes. Determine how much free space is on the hard drive and
how much you want to allocate for a new swap partition. At the (parted) prompt, type
mkpartfs part-type
linux-swap start
end, where
part-type is one of primary,
extended, or logical, start is the
starting point of the partition, and
end is the end point of the
partition.  | Warning |
|---|
| | Changes take place immediately; be careful when you type. |
Exit parted by typing
quit.
Now that you have created the swap partition, use the command
mkswap to setup the swap partition. At a shell
prompt as root, type the following:
To enable the swap partition immediately, type the following
command:
To enable it at boot time, edit /etc/fstab
to include: /dev/hdb2 swap swap defaults 0 0 |
The next time the system boots, it enables the new swap
partition.
After adding the new swap partition and enabling it, verify it is
enabled by viewing the output of the command cat
/proc/swaps or free.
To add a swap file:
Determine the size of the new swap file in megabytes and multiple by 1024 to
determine the block size. For example, the block size of a 64 MB swap
file is 65536. At a shell prompt as root, type the following command with
count being equal to the desired block size: dd if=/dev/zero of=/swapfile bs=1024 count=65536 |
Setup the swap file with the command: To enable the swap file immediately but not automatically at
boot time: To enable it at boot time, edit /etc/fstab
to include: /swapfile swap swap defaults 0 0 |
The next time the system boots, it enables the new swap
file.
After adding the new swap file and enabling it, verify it is
enabled by viewing the output of the command cat
/proc/swaps or free.
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