Installable software for Linux is mainly packaged as .rpm (for RedHat) & .deb (for Ubuntu & other debian based distributions).
There can be cases when you want to install some application on your Ubuntu system & the same application might only be available as .rpm. Recently, I was in a similar situation when I had to install IBM WebSphere MQ; but the installation package was availabe only in RPM format.
In such cases, you can use the alien package converter to convert the .rpm to .deb.
You can install alien using the following command –
sudo apt-get install alien
After alien has been installed, you can convert a .rpm to .deb using:
alien <rpm package file name>
After you have the .deb file, you can install the package using:
dpkg -i <deb package file name>