The configuration files upgrade is a complex process, during which many problems may arise. The root cause of all problems are the users’ customizations made in the configuration files in places that also change in a newer version. Because the upgrade process tries to apply changes from newer versions to existing files, the tool can be confused when it reaches the incompatibly modified part.

In case of a problem, the upgrade process terminates and leaves the state of configuration files unchanged. There is no automatic mechanism preconfigured, but the user has to instruct the tool on how to resolve the problem. This is done by specifying patch modes globally for the whole process, for a particular file, or for a particular file and (intermediate) version we upgrade to.

Patch Modes

The way the upgrade process works is a typical diff/patch approach. Each version change is described as a series of patch operations that must be applied. During the patching, some of the following problems may arise:

  • A parameter has been removed by the user, but the patch tries to change it.

  • The data structure of the parameter isn’t the expected one.

  • Precise location for the change can’t be found.

To deal with these situations, there are the following patch modes available:

Patch Modes


Problem Cause


Skip patch operation

Removed or incompatible configuration part.


Place value in any suitable place, instead of precise place.

No precise place for application found.


Replace user changed values with new default ones.

User changed value for which new default appeared.

The patch modes are specified using the --patch-modes MODES parameter passed to the onecfg upgrade. Patch modes can be used multiple times but the most specific one always overrides the more general ones (patch mode for particular file/version overrides the default patch mode). The syntax of the parameter should follow one of the following syntaxes:

  • MODES - default patch modes MODES for all files and all versions.

  • MODES:FILE_NAME - patch modes MODES for specific file FILE_NAME and all its versions

  • MODES:FILE_NAME:VERSION - patch modes MODES for specific file FILE_NAME when upgraded to version VERSION

Modes (MODES) is a comma (,) separated list of selected patch modes (skip, force, replace).

Default Safe Patch Modes

Each different type of file you can find here has the following default safe patch mode:

File Type

Default Patch Mode

Plain file




YAML w/ ordered arrays






These default patching modes can be used in the upgrade process (onecfg upgrade) using the parameter --patch-safe.


Set default patch mode to skip problematic places for all files in any version:

onecfg upgrade --patch-modes skip

Set patch mode to skip problematic places only for /etc/one/oned.conf. Leave unspecified mode for the rest of the files:

onecfg upgrade --patch-modes skip:/etc/one/oned.conf

Set patch mode to skip only for /etc/one/oned.conf when upgraded to version 5.6.0. The remaining files have the unspecified mode:

onecfg upgrade --patch-modes skip:/etc/one/oned.conf:5.6.0

Example of multiple patch modes for multiple files:

onecfg upgrade \
    --patch-modes skip:/etc/one/oned.conf \
    --patch-modes skip,replace:/etc/one/oned.conf:5.10.0 \
    --patch-modes force:/etc/one/sunstone-logos.yaml:5.6.0 \
    --patch-modes replace:/etc/one/sunstone-server.conf \
    --patch-modes skip:/etc/one/sunstone-views/admin.yaml:5.4.1 \
    --patch-modes skip:/etc/one/sunstone-views/admin.yaml:5.4.2 \
    --patch-modes skip:/etc/one/sunstone-views/kvm/admin.yaml

Restore from Backup

Upgrade operations are done safely on a copy of production configuration files without changing the system state. After the upgrade ends successfully, the modified files are copied back to production locations.


Each upgrade operation creates a backup of current directories with OpenNebula configuration files into /var/lib/one/backups/config/. In case of error when copying the modified state back to production locations, the automatic restore is triggered.

In the case of a catastrophic failure when even automatic restore fails, the original content of configuration directories must be restored manually from initial backup. Here’s an example of a failed upgrade which requires manual intervention:

onecfg upgrade
ANY   : Backup stored in '/tmp/onescape/backups/2019-12-18_12:22:28_2891'
FATAL : Fatal error on restore, we are very sorry! You have to restore following directories manually:
    - copy /tmp/onescape/backups/2019-12-18_12:22:28_2891/etc/one into /etc/one
    - copy /tmp/onescape/backups/2019-12-18_12:22:28_2891/var/lib/one/remotes into /var/lib/one/remotes
FATAL : FAILED - Data synchronization failed