OpenStack upgrade levels

OpenStack upgrade levels

The depth of the upgrade can differ depending on a use case. The following table describes the possible upgrade levels.

Levels of upgrade



Application upgrade

Only application packages are upgraded. Includes upgrade of application dependencies to the desired level.

System packages upgrade

Known as apt-get upgrade. Used to install the newest versions of all currently installed packages on the system from the sources enumerated in /etc/apt/sources.list. The packages are retrieved and upgraded. Under no circumstances, the packages are removed. The packages that are not yet installed but required are retrieved and installed. The new versions of the currently installed packages that cannot be upgraded without changing the installation status of another package or packages are left at their current version. An update must be performed first, so that apt-get can know that the new versions of the packages are available.

Kernel upgrade

Known as apt-get dist-upgrade. In addition to performing the function of upgrade, handles the changing dependencies with new versions of packages. The apt-get tool has a smart conflict resolution system and attempts to upgrade the most important packages at the expense of less important ones if necessary. The dist-upgrade command can remove some packages. The /etc/apt/sources.list file contains the list of locations from which the desired package files should be retreived. Reboot might be needed after this type of upgrade.

Release upgrade

Known as a do-release-upgrade upgrade of a Linux distribution to a newer major release.


To minimize the control plane downtime, we recommend performing the application level upgrade first. When the OpenStack component is fully upgraded, proceed with the system upgrade. For details, see The OpenStack formulas structure.