Akonadi and AddressBook
Note
This information was provided by Tobias Koenig, KDE-PIM developer.
Some Definitions
- Real data
- By real data we mean the data, like the contacts or events. These data are stored either on a groupware server or in local files. Where exactly depends on the resource you are using. E.g. the Personal Contacts resource stores its data under $XDG_DATA_HOME/contacts.
- Cached data
- The cached data are copies of the real data that are kept in the database for faster access and offline caching. The database also keeps the meta data which are management data needed by Akonadi to work correctly.
- Configuration data
- The configuration data are the data that configure the Akonadi server and the individual resources. The general configuration data for the server can be found under $XDG_CONFIG_HOME/akonadi. The configuration data for each indvidual resources are stored under $XDG_CONFIG_HOME/akonadi_xyz_resourcerc# (xyz is name of resource and # its instance number).
- The Akonadi server configuration is a couple of files in $XDG_CONFIG_HOME/akonadi. It contains which data sources and helper programs are active and will be started and watched (so they can be restarted on crashes) by one of Akonadi's server processes (akonadi_control).
- Each data source handler (called resources) or helper program (called agents) can have its own configuration although some agents or resources don't require configuration. The general rule is that for every entry in $XDG_CONFIG_HOME/akonadi/agentsrc there is a corresponding configuration file in $XDG_CONFIG_HOME. For example, if the [Instances] section in agentrc contains an entry for akonadi_ical_resource_2, there is also a config file called akonadi_ical_resource_2rc in the $XDG_CONFIG_HOME directory.
- Depending on the type of data, such config files for resources will have filenames or directory names of where the data is stored. Common locations are KDE's legacy default files, e.g. $HOME/.kde/share/apps/korganizer/std.ics. New default locations are files and directories in $XDG_DATA_HOME, e.g. $XDG_DATA_HOME/contacts.
Organising Backups
So now we need to decide what to back up. If you want to backup the "real data", then it depends on the resources you have configured... if you use a groupware server, then the backup should be done there. For contacts, the files under $XDG_DATA_HOME/contacts will normally be what you need.
To back up the entire Akonadi configuration, including which resources are active and their configuration, you can use the pimdataexporter' tool. This, however doesn't back up the Akonadi database containing the cached data and, unfortunately, after restoring the configuration (using the pimdataexporter again), Akonadi will have to re-fetch all data again into its cache. This can cause configuration that points to actual mail folders or calendars to get broken and accidentally point to another folder.
After restoring configuration and syncing all data, it's vital to manually check all folder configuration, especially in KMail identities and make sure the folders are configured properly.