[update-config] Create a backup of the local UCI configuration to be able to set it back to its original state

[okraits]

Right now openwisp-config doesn't keep a backup of the local UCI configuration (all files in /etc/config).

This can lead to situations where settings are lost:

1. An existing section is modified by openwisp-config.
2. The modifications are removed from the configuration tarball delivered by openwisp-controller.
3. openwisp-config deletes this section instead of restoring the state it had before it was modified by OW2.

Thus a backup of the initial configuration should be created and restored when the modifications are removed.

[nemesifier]

Once this, #71 and #69 are fixed the config update process will be improved greatly!

[BlancLoup]

Problem:
IMHO that it's not the right way. The real problem is backup realized like "sysupgrade -b". Sysupgrade does not match "principles" of apply_configuration function. Apply_configuration does correct actions for "diff-like" configurations while sysupgrade saves the entire configuration (including /etc/config/openwisp).

Consequences:

1. apply_configuration always restores /etc/config/openwisp that leads to openwisp agent restarting before restore process was completed. Integrity will be ruined.
2. all daemons will be restarted even that is not need.

Solution (backup only files that will be changed, very simpled algorithm):

1. check new configuration archive for files that will be changed:
   tar -ztf $configuration_archive_to_apply | sed 's/^///' > $list_of_files_will_be_changed
2. create backup archive of files that will be changed
   tar -czvf $backup_of_current_files -T $list_of_files_will_be_changed

[okraits]

I don't understand what you're trying to say. The use of sysupgrade hasn't been changed and it's not involved here at all.

The issue addressed here is that if openwisp-config modifies an element twice then it has no history available to tell wether the element was originally either added or modified by openwisp-config. Thus it is not able to restore the original state. This change fixes that.

[BlancLoup]

Sorry... I mixed up a little bit.

[okraits]

If you have valid and serious concerns about my changes then please speak up and elaborate. It might be possible that I failed to get your point. Maybe @nemesisdesign can also add his take on this.

[nemesifier]

@BlancLoup where you mixing this issue with #81?

[Gobiviswa]

Hi, I am just thinking what is the need of deleting the files when update the configurations? is there any specific reason for that? By the way, is this issue resolved ?
Thanks,

[okraits]

Today a workmate of mine had the issue that an outdated backup of /etc/config/openwisp was present in /etc/openwisp/stored/etc/config/openwisp.

When he applied changes to /etc/config/openwisp and later removed those changes, the outdated backup was used to restore the original state.

Which led to the issue that openwisp-config used a wrong uuid/key to fetch the checksum from the controller. I have to look into that and fix it.