Delta RPMs on Yum

Delta, in sense of file, refers to the difference between two versions of the file. So, if you have a file and its delta, you can create a new file with all the changes included.

Delta RPMs are exactly the same. Consider a package 'yum-1.2.30-x86-64.rpm' and another updated package 'yum-1.2.31-x86-64'. A delta RPM of this package will be able to recreate the new updated Yum package from the older package available in the system. Since Delta RPMs are just the difference in two packages, they are small in size(in most cases). So, delta RPMs are useful if you have a congested, slow or limited bandwidth.

Enabling the use of Delta RPM in Yum:
We need 'yum-presto' plugin to enable delta RPMs. Install it as:

# yum install yum-presto

Now, try updating your system as:

# yum update

You will see that the download size will reduce dramatically and updates will be faster. That's how Delta RPM works.

Tested on CentOS 6.2.

Zypper implements delta RPMs by default. So, openSUSE users need not to be worry and there is nothing to enable for openSUSE systems.