Pattern - Yum
The Yellow dog Updater, Modified (YUM), is a package manager for RPM-based systems. It is documented online, and hosted at Duke University
The tool can
- Bring a machine up to date
- Install a package and all its dependencies on demand
- Uninstall a package on demand, checking its dependencies first
Features
- Command line and GUI tools to keep an RPM-based Linux distribution up to date.
- Uses RPM metadata to determine dependency information.
- Client applications to poll Yum repositories for changes.
- Pulls down artifacts on demand from a remote repository.
- Atomic update process; if an update fails, all the components already installed as part of the transaction are rolled back.
- Supports multiple repositories and GPG-key validation of signed artifacts.
- 'Pinning' can be used to keep an artifact fixed at a specific version.
Advantages
- Lets users install new packages easily.
- Keeping machines up to date reduces security risks.
- Custom Yum repositories can be created.
Disadvantages
- No easy way to roll back an update once it has completed. This complicates cluster-wide updates, where an update must only go through if all systems upgrade successfully. If one machine in the cluster fails to upgrade, it should be rolled back from all systems, even those who successfully upgraded. (this can be done, look for "downgrade" in the documentation, but it is an option that needs to be enabled)
- No easy way to programmatically determine the success/failure of operations other than screen-scraping.
- Defaults to pulling down the 32-bit and 64-bit versions on x86_64 hosts.
- Can be slow
- Reportedly, no way to 'pin' an artifact in a new installation; when you first install something, you get the latest version.
SmartFrog support
SmartFrog RPMs can be deployed and updated through Yum. There is no explicit support for creating Yum repositories or managing upgrade and rollback.