Akonadi（數據存儲）

介紹

在 KDE 軟體集（KDE Software Compilation）4.4 中，通訊錄（KAddressBook）成為首個應用Akonadi的應用程式。在早期的移植階段中不可避免的存在各種小問題，疑難排解頁面將有助於解決它們。要簡單的了解Akonadi的用途，可以瀏覽術語-Akonadi。那你也能找到指向進一步閱讀的有用鏈接。一旦這些不可避免的早期問題解決後，Akonadi 將會通過眾多程式提供源源不斷的可用性。

Currently, all KDE PIM applications with the exception of Akregator are using Akonadi to access user's PIM data.

Controlling Akonadi

Akonadi will start automatically in the background when any application using it is started.

To manually start, stop or restart Akonadi, you can use the akonadictl command from the commandline. Using this method, you can get additional useful information on the console.

To start the Akonadi server,

akonadictl start

To stop the Akonadi server,

akonadictl stop

To restart a running Akonadi server,

akonadictl restart

To query the status of the Akonadi server,

akonadictl status

Disabling the Akonadi subsystem

The Akonadi server is automatically started by any Akonadi-enabled application. If you don't want Akonadi to be started after login, you have to ensure that no Akonadi-enabled application is launched at login or thereafter. Remember to check Plasma applets as well — the Digital Clock widget in the default panel, for instance uses Akonadi to (optionally) display calendar events and this is enabled in its settings by default (see the "Display Events" option) . You must remove any widgets that may start it from your start-up, if you wish Akonadi to start only when you start KMail or other applications.

Remember

If you don't want to have Akonadi running on your system at all, you can not use any of the Akonadi-enabled applications, such as KMail, KOrganizer or KAddressbook. Such applications will not work when Akonadi is disabled using the steps below. Also note, that some Plasma widgets, such as the Digital Clock uses Akonadi.

To ensure that Akonadi is not started, check that no applications require it at login. In particular, open the Plasma clock applet preferences, go to Calendar and uncheck Show events to prevent Plasma from requesting information from Akonadi and thus allowing it to start.

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.

Backup

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.

Frequently Asked Questions

Where is my data now?

Your data are safely stored outside of Akonadi control on your disk (e.g. local maildir folder or iCal calendar), or on a remote server (in case of e.g. email over IMAP or events from a CalDAV calendar). Akonadi will optionally store a copy of this data in its database to allow applications to quickly retrieve and display them. Any modifications done to data in the Akonadi database will be synced to the actual storage. The main advantage of using the database as a cache is that remote PIM data are available even when you are offline, and you can still interact with them (e.g. mark emails as read or move them, create new events, reschedule existing meetings etc.) and all the changes will get synced automatically once you connect to the internet again.

Thus, deleting the Akonadi database will not cause any data to be lost (as long as all pending changes are synced).

How to upgrade my PostgreSQL database?

After updating your PostgreSQL server to a new major version, sometimes you will have to convert your Akonadi database for use with this new version. Instructions can be found on this page.

Migration problems

Akonadi's Glossary entry has a brief description of Akonadi's purpose, and other useful links.

How do I switch from MySQL/PostgreSQL to SQLite?

Since Akonadi 6 akonadi-db-migrator is included in akonadi that allows you to switch the database backend. Where for previous versions this involved deleting and recreating the database a migration is now properly supported by akonadi.

The tool needs to be called with the parameter --newengine to chose to which backend it should to: {{{

 --newengine <ENGINE>       The new DB engine to use. Possible values are 
                            "sqlite", "mysql" and "postgres"

}}}

For example: {{{ akonadi-db-migrator --newengine sqlite }}}