Introduction to D-BUS
D-BUS is a message bus system, a
simple way for applications to talk to one another. D-BUS supplies both a system daemon (for
events such as “new hardware device
added” or “printer queue
changed”) and a per-user-login-session daemon (for
general IPC needs among user applications). Also, the message bus
is built on top of a general one-to-one message passing framework,
which can be used by any two applications to communicate directly
(without going through the message bus daemon).
Package Information
D-BUS Dependencies
Required
expat-2.0.1 or both pkg-config-0.22 and
libxml2-2.6.31
Optional
X Window
System, Doxygen-1.5.2 (to generate the API
documentation), and xmlto (to generate HTML
documentation and manuals)
User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/dbus
Installation of D-BUS
As the root user, create a system
user and group to handle the system message bus activity:
groupadd -g 18 messagebus &&
useradd -c "D-BUS Message Daemon User" -d /dev/null \
-u 18 -g messagebus -s /bin/false messagebus
This package's test suite cannot be run without passing additional
parameters to configure and exposing additional
functionality in the binaries. These interfaces are not intended to
be used in a production build of D-BUS, so it will have to be built twice in
this situation. If you would like to run the unit tests, issue the
following commands:
./configure --enable-tests &&
make &&
make check &&
make distclean
Install D-BUS by running the
following commands (you may wish to review the output from
./configure --help
first and add any desired parameters to the configure command shown below):
./configure --prefix=/usr \
--sysconfdir=/etc \
--localstatedir=/var &&
make
The --enable-doxygen-docs parameter
does not work properly. If you have Doxygen installed and you wish to build the
API documentation, issue doxygen.
Now, as the root user:
make install &&
install -v -m755 -d /usr/share/doc/dbus-1.0.2 &&
install -v -m644 doc/{TODO,*.{dtd,xml,xsl,txt,c}} \
/usr/share/doc/dbus-1.0.2
If you built the HTML documentation, install it by issuing the
following commands as the root
user:
install -v -m644 doc/*.html /usr/share/doc/dbus-1.0.2
If you built the API documentation, install it by issuing the
following commands as the root
user:
install -v -m755 -d /usr/share/doc/dbus-1.0.2/api \
/usr/share/man/man3dbus &&
install -v -m644 doc/api/html/* \
/usr/share/doc/dbus-1.0.2/api &&
install -v -m644 doc/api/man/man3dbus/* \
/usr/share/man/man3dbus
Configuring dbus
Config Files
/etc/dbus-1/session.conf,
/etc/dbus-1/system.conf and
/etc/dbus-1/system.d/*
Configuration Information
The configuration files listed above should probably not be
modified. If changes are required, you should create /etc/dbus-1/session-local.conf and/or
/etc/dbus-1/system-local.conf and
make any desired changes to these files.
If any packages install a D-Bus
.service file outside of the
standard /usr/share/dbus-1/services
directory, that directory should be added to the local session
configuration. For instance, /usr/local/share/dbus-1/services can be added
by performing the following commands as the root user:
cat > /etc/dbus-1/session-local.conf << "EOF"
<!DOCTYPE busconfig PUBLIC
"-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
"http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
<!-- Search for .service files in /usr/local -->
<servicedir>/usr/local/share/dbus-1/services</servicedir>
</busconfig>
EOF
Boot Script
To automatically start dbus-daemon when the system is
rebooted, install the /etc/rc.d/init.d/dbus bootscript from the
blfs-bootscripts-20080816 package.
make install-dbus
Note that this boot script only starts the system-wide
D-BUS daemon. Each user
requiring access to D-BUS
services will also need to run a session daemon as well. There
are many methods you can use to start a session daemon using the
dbus-launch
command. Review the dbus-launch man page for
details about the available parameters and options. Here are some
suggestions and examples:
-
Add dbus-launch to the line
in the ~/.xinitrc file that
starts your graphical desktop environment as shown in
the section called
“Configuring the Core GNOME Packages”.
-
If you use xdm or some other display
manager that calls the ~/.xsession file, you can add
dbus-launch
to the line in your ~/.xsession file that starts your
graphical desktop environment. The syntax would be similar
to the example in the ~/.xinitrc file.
-
If you use gdm or some other display
manager that utilizes custom files to initiate sessions,
use the example in the section called
“Configuration Information” of the
GDM instructions to create
a file containing dbus-launch.
-
The examples shown previously use dbus-launch to specify a
program to be run. This has the benefit (when also using
the --exit-with-session
parameter) of stopping the session daemon when the
specified program is stopped. You can also start the
session daemon in your system or personal startup scripts
by adding the following lines:
# Start the D-BUS session daemon
eval `dbus-launch`
export DBUS_SESSION_BUS_ADDRESS
This method will not stop the session daemon when you exit
your shell, therefore you should add the following line to
your ~/.bash_logout file:
# Kill the D-BUS session daemon
kill $DBUS_SESSION_BUS_PID
-
A hint has been written that provides ways to start scripts
using the KDM session manager of KDE. The concepts in this
hint could possibly used with other session managers as
well. The hint is located at
http://www.linuxfromscratch.org/hints/downloads/files/execute-session-scripts-using-kdm.txt.