Some packages are held by more than one repository. The priorities plugin choose packages from the highest-priority repository, excluding duplicate entries from other repos.


$ cat /etc/yum/pluginconf.d/priorities.conf


yum erase yum-plugin-priorities

Listing excluded packages

yum list updates -d3


Errno -3: Error performing checksum


  • Description: This happened on a CentOS 5 host when running YUM against a pulp-server on CentOS 6. Running $ sudo yum makecache never finished without this error message and running Puppet did not succeed either.

  • Solution: "What this really means that yum is too stupid to calculate the sha256 checksum correctly (and also too stupid to give you a sensible error message like "Sorry, primary.sqlite.bz2 is using a sha256 checksum, but I don't know how to calculate that")."

    The fix is simple:

    bash (client)$ sudo yum install python-hashlib

    When running YUM against a pulp server, make sure the repository on a >CentOS 5.5 pulp server has been created with the right SHA setting (--checksum-type sha1)

    text ... [Errno -3] Error performing checksum ...

Package group/Environment group


For (at least CentOS 7) Yum splits things up into Package groups and Environment groups.

Depending on what shall be installed a different syntax must be used:

  • Package group: yum install -y @package, e.g. yum install -y @developer-tools
  • Environment group: yum install -y @^environment_group, e.g. yum install -y "@^Server with GUI"


Show the last yum executions

yum history