# using mock to test rpm packages

Our PkgForge service is a locally developed build farm. We use this for automatically building .src.rpm files for the multiple platforms and architectures we often have to support concurrently . The service uses Mock underneath. It works very well for known working packages and a “send and forget” approach. It is not so good however for debugging build issues (although that was never its intended purpose). Really hit this recently when trying to build a new locally developed package for wider distribution. Being used to only having a few issues to resolve normally (commonly just missing pre-requisite packages), started off using the build farm service. But the numerous iterations needed and the slow rebuild cycles were getting tedious. Eventually an issue that really needed direct access to the build root to debug was the final nail in the coffin. Previously been put off using Mock manually by assuming that it would be complicated. Turns out it is an absolute breeze and definitely the way to pre-test, or even final build if you want speed and controlled (re)submission, new packages (particularly when you only need to worry about distribution for one architecture and platform). So here is a brief howto (as root).
 yum install mock 
Mock comes with the necessary configuration file for our main current platform and architecture  already, so in principle you need do nothing more than:
 mock -r epel-7-x86_64.cfg --rebuild PACKAGE.src.rpm 
You can then follow the output live as it builds. If you are running this on your desktop you will also find it runs refreshingly fast. The build root and results are also kept around for subsequent analysis in:
 /var/lib/mock/epel-7-x86_64/root /var/lib/mock/epel-7-x86_64/result/{build,root,state}.log 
Commonly you may need to include our own local repositories. This is also simple, for example to use our “inf” repository:
 cp /etc/mock/epel-7-x86_64.cfg /tmp 
Edit and add the following within the set of repositories :
 [el7inf] name=el7inf baseurl=http://http.pkgs.inf.ed.ac.uk/rpms/os/el7/x86_64/inf priority=1 enabled=1 gpgcheck=0 
then:
 mock -r /tmp/epel-7-x86_64.cfg --rebuild PACKAGE.src.rpm 
If you get failures during build you can simply chroot and test the build environment, do further debugging and manual package/file installations and rebuilds:
 chroot /var/lib/mock/epel-7-x86_64/root 
Note to the wicked: if you are using Java you are likely to find that after doing the chroot you also need to do:
 mount -t proc none /proc 

PkgForge can automatically build multiple locally dependent packages in one go. If you need to do this with a local mock setup then you need to manually build each package one by one and submit them so they are accessible to mock (or you could investigate the feature of mock that means it can dynamically generate and update a yum repository from the results of previous builds).