Add more swap space to a running Linux system

Today I was trying to install Oracle XE to a Centos 5 installation using this guide. While installing the packages i noticed that the Oracle XE Database was unable to install. The error message was quite clear:

This system does not meet the minimum requirements for swap space.  Based on
the amount of physical memory available on the system, Oracle Database 10g
Express Edition requires 1024 MB of swap space. This system has 509 MB
of swap space.  Configure more swap space on the system and retry the installation.
error: %pre(oracle-xe-univ-10.2.0.1-1.0.i386) scriptlet failed, exit status 1
error:   install: %pre scriptlet failed (2), skipping oracle-xe-univ-10.2.0.1-1.0

My solution was to adding some temporary swap space to this system, which is really easy to do:

Step 1. Create an empty file called /swapfile from about 600MB

root@bootux:~# dd if=/dev/zero of=/swapfile bs=1024000 count=600
600+0 records in
600+0 records out
614400000 bytes (614 MB) copied, 5.85153 seconds, 105 MB/

Step 2. Format the new file to make it a swap file

root@bootux:~# mkswap /swapfile
Setting up swapspace version 1, size = 614395 kB

Step 3. Enable the new swapfile. Only the swapon command is needed, but with the free command you can clearly see the swap space is made available to the system.

root@bootux:~# free -m | grep Swap
Swap:          509          0        509
root@bootux:~# swapon /swapfile
root@bootux:~# free -m | grep Swap
Swap:         1095          0       1095

Installation can now continue :)

Easily create a RAM-disk in Linux

This command creates a 2GB RAM-disk and mounts it to /tmp/space.

$ mkdir /tmp/space
$ sudo mount -t tmpfs tmpfs /tmp/space -o size=2G,nr_inodes=200k,mode=01777

You should now have an extra 2GB storage device.

 $ df -h | grep space
$ tmpfs                 2.0G     0  2.0G   0% /tmp/space

You access the temporarily device by it's mountpoint /tmp/space. Needless to say, once you unmount this volume (for instance, with a reboot), the data on it will be gone. Use with care! :) Tested on Ubuntu, should work with any 2.4 or 2.6 kernel...