Posted on 15-12-2010
Filed Under (Linux commands, Redhat & Fedora, UNIX/Linux) by Ravi Bhure

Introduction –

Here we are going to create 4G swap file using cmd ‘dd’, later we will activate it.
we are named and create ‘/extraswap’ swap file for additional swap

dd command options
if = input file (read from FILE instead of stdin)
of = output file name (write to FILE instead of stdout)
bs = BYTES rate
count = BLOCKS (copy only number of block)

dd if=/dev/zero of=/extraswap bs=1024 count=4096000

***Adding extraswap Swap file

[root@ravi ~]# dd if=/dev/zero of=/extraswap bs=1024 count=4096000
4096000+0 records in
4096000+0 records out
4194304000 bytes (4.2 GB) copied, 162.277 seconds, 25.8 MB/s

Set up a Linux swap area using ‘mkswap’ command

[root@ravi ~]# mkswap /extraswap
Setting up swapspace version 1, size = 4194299 kB

Activate swap using ‘swapon’ command

[root@ravi ~]# swapon /extraswap

[root@ravi ~]# free -m
total       used       free     shared    buffers     cached
Mem:         16053       6148       9905          0        293       5488
-/+ buffers/cache:        367      15686
Swap:         3999          0       3999

Edit /etc/fstab and put below entry into it to swap on automatic after reboot server

/extraswap              none                    swap    defaults        0 0

*** Remove /extraswap file

[root@ravi ~]# swapoff /extraswap

Remove /extraswap swap file entry from /etc/fstab and run ‘mount -a

Delete /extraswap

[root@ravi ~]# rm /extraswap


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