NAME

       dconf - A configuration system

DESCRIPTION

       dconf is a simple key/value storage system that is heavily optimised for reading. This
       makes it an ideal system for storing user preferences (which are read 1000s of times for
       each time the user changes one). It was created with this usecase in mind.

       All preferences are stored in a single large binary file. Layering of preferences is
       possible using multiple files (ie: for site defaults). Lock-down is also supported. The
       binary file for the defaults can optionally be compiled from a set of plain text keyfiles.

       dconf has a partial client/server architecture. It uses D-Bus. The server is only involved
       in writes (and is not activated in the user session until the user modifies a preference).
       The service is stateless and can exit freely at any time (and is therefore robust against
       crashes). The list of paths that each process is watching is stored within the D-Bus
       daemon itself (as D-Bus signal match rules).

       Reads are performed by direct access (via mmap) to the on-disk database which is
       essentially a hashtable. For this reason, dconf reads typically involve zero system calls
       and are comparable to a hashtable lookup in terms of speed. Practically speaking, in
       simple non-layered setups, dconf is less than 10 times slower than GHashTable.

       Writes are assumed only to happen in response to explicit user interaction (like clicking
       on a checkbox in a preferences dialog) and are therefore not optimised at all. On some
       file systems, dconf-service will call fsync() for every write, which can introduce a
       latency of up to 100ms. This latency is hidden by the client libraries through a clever
       "fast" mechanism that records the outstanding changes locally (so they can be read back
       immediately) until the service signals that a write has completed.

       The binary database format that dconf uses by default is not suitable for use on NFS,
       where mmap does not work well. To handle this common use case, dconf can be configured to
       place its binary database in XDG_RUNTIME_DIR (which is guaranteed to be local, but
       non-persistent) and synchronize it with a plain text keyfile in the users home directory.

PROFILES

       A profile is a list of configuration databases that dconf consults to find the value for a
       key. The user's personal database always takes the highest priority, followed by the
       system databases in the order prescribed by the profile.

       On startup, dconf consults the DCONF_PROFILE environment variable. If set, dconf will
       attempt to open the named profile, aborting if that fails. If the environment variable is
       not set, it will attempt to open the profile named "user" and if that fails, it will fall
       back to an internal hard-wired configuration. dconf stores its profiles in text files.
       DCONF_PROFILE can specify a relative path to a file in /etc/dconf/profile/, or an absolute
       path (such as in a user's home directory). The profile name can only use alphanumeric
       characters or '_'.

       A profile file might look like the following:

           user-db:user
           system-db:local
           system-db:site

       Each line in a profile specifies one dconf database. The first line indicates the database
       used to write changes, and the remaining lines indicate read-only databases. (The first
       line should specify a user-db or service-db, so that users can actually make configuration
       changes.)

       A "user-db" line specifies a user database. These databases are found in
       $XDG_CONFIG_HOME/dconf/. The name of the file to open in that directory is exactly as it
       is written in the profile. This file is expected to be in the binary dconf database
       format. Note that XDG_CONFIG_HOME cannot be set/modified per terminal or session, because
       then the writer and reader would be working on different DBs (the writer is started by
       DBus and cannot see that variable).

       A "service-db" line instructs dconf to place the binary database file for the user
       database in XDG_RUNTIME_DIR. Since this location is not persistent, the rest of the line
       instructs dconf how to store the database persistently. A typical line is
       service-db:keyfile/user, which tells dconf to synchronize the binary database with a plain
       text keyfile in $XDG_CONFIG_HOME/dconf/user.txt. The synchronization is bi-directional.

       A "system-db" line specifies a system database. These databases are found in
       /etc/dconf/db/. Again, the name of the file to open in that directory is exactly as it is
       written in the profile and the file is expected to be in the dconf database format.

       If the DCONF_PROFILE environment variable is unset and the "user" profile can not be
       opened, then the effect is as if the profile was specified by this file:

           user-db:user

       That is, the user's personal database is consulted and there are no system settings.

KEY FILES

       To facilitate system configuration with a text editor, dconf can populate databases from
       plain text keyfiles. For any given system database, keyfiles can be placed into the
       /etc/dconf/db/database.d/ directory. The keyfiles contain groups of settings as follows:

           # Some useful default settings for our site

           [system/proxy/http]
           host='172.16.0.1'
           enabled=true

           [org/gnome/desktop/background]
           picture-uri='file:///usr/local/rupert-corp/company-wallpaper.jpeg'

       After changing keyfiles, the database needs to be updated with the dconf(1) tool.

LOCKS

       System databases can contain 'locks' for keys. If a lock for a particular key or subpath
       is installed into a database then no database listed above that one in the profile will be
       able to modify any of the affected settings. This can be used to enforce mandatory
       settings.

       To add locks to a database, place text files in the /etc/dconf/db/database.d/locks
       directory, where database is the name of a system database, as specified in the profile.
       The files contain list of keys to lock, on per line. Lines starting with a # are ignored.
       Here is an example:

           # prevent changes to the company wallpaper
           /org/gnome/desktop/background/picture-uri

       After changing locks, the database needs to be updated with the dconf(1) tool.

PORTABILITY

       dconf mostly targets Free Software operating systems. It will theoretically run on Mac OS
       but there isn't much point to that (since Mac OS applications want to store preferences in
       plist files). It is not possible to use dconf on Windows because of the inability to
       rename over a file that's still in use (which is what the dconf-service does on every
       write).

API STABILITY

       The dconf API is not particularly friendly, and is not guaranteed to be stable. Because of
       this and the lack of portability, you almost certainly want to use some sort of wrapper
       API around it. The wrapper API used by GTK+ and GNOME applications is GSettings[1], which
       is included as part of GLib. GSettings has backends for Windows (using the registry) and
       Mac OS (using property lists) as well as its dconf backend and is the proper API to use
       for graphical applications.

SEE ALSO

       dconf-service(1), dconf-editor(1), dconf(1), GSettings[1]

NOTES

        1. GSettings
           http://developer.gnome.org/gio/stable/GSettings.html