Installing RPMs on Ubuntu

Method 1

1. Install rpm
$ sudo aptitude install rpm

Along with other things it would install rpm2cpio. (RPM and initramfs use the CPIO archiver)

2. Extract the contents of the RPM
$ rpm2cpio < some-package.rpm | cpio -i --make-directories --verbose

3. Copy over the required files to the different directories.

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Method 2

1. Install alien
$ sudo aptitude install alien

2. Covert the .rpm to .deb
$ sudo alien --to-deb --scripts --verbose some-package.rpm

NOTE: Alien internally uses rpm2cpio, so make sure you have installed rpm.

--scripts : If the .rpm has scripts then you need to include those

3. Install the .deb file.
sudo dpkg -i some-package.deb

The advantage of converting it to .deb and installing using dpkg is that you can manage the install\uninstall\reinstall and version using apt\aptitude.