Ubuntu comes with package management system, apt. you can easily use apt-get to install or remove package in the other words install or remove software (program) on your ubuntu machine.

Uninstall Package on Ubuntu 11.10

Installing software command
apt-get install packagename
for example
apt-get install bind9

removing software command
apt-get remove packagename
for example
apt-get remove bind9

in case there was a problem with package configuration maybe you want to remove certain package with all of its configurations that have been saved by the time we install the package.

for example when i try to reinstall bind9 on my ubuntu

* Starting domain name service… bind9 [fail]
invoke-rc.d: initscript bind9, action “start” failed.
dpkg: error processing bind9 (–configure):
subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
bind9
E: Sub-process /usr/bin/dpkg returned an error code (1)

there seems error in configuration previously set. so i need to remove all its configuration files that usually are left when we just do apt-get remove.

to remove package configurations use this command

[php]dpkg –purge packagename[/php]
for example in mycase
[php]dpkg –purge bind9[/php]

then when you reinstall the program “apt-get install” will work as before.