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).
Note
Development versions of BLFS may not build or run some packages properly if LFS or dependencies have been updated since the most recent stable versions of the books.
Package Information
D-Bus Dependencies
Recommended
Xorg Libraries (for dbus-launch program)
Optional
For the tests: D-Bus Python-1.3.2, PyGObject-3.46.0, and Valgrind-3.22.0; for documentation: Doxygen-1.10.0, xmlto-0.0.28, Ducktype, and Yelp Tools
Installation of D-Bus
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 \
--runstatedir=/run \
--disable-doxygen-docs \
--disable-xml-docs \
--disable-static \
--with-systemduserunitdir=no \
--with-systemdsystemunitdir=no \
--docdir=/usr/share/doc/dbus-1.14.10 \
--with-system-socket=/run/dbus/system_bus_socket &&
make
See below for test instructions.
Now, as the root
user:
make install
If you are using a DESTDIR install, dbus-daemon-launch-helper needs to be fixed afterwards. Issue, as root
user:
chown -v root:messagebus /usr/libexec/dbus-daemon-launch-helper &&
chmod -v 4750 /usr/libexec/dbus-daemon-launch-helper
If you are still building your system in chroot or you did not start the daemon yet, but you want to compile some packages that require D-Bus, generate the D-Bus UUID to avoid warnings when compiling some packages with the following command as the root
user:
dbus-uuidgen --ensure
If using elogind-252.9, create a symlink to the /var/lib/dbus/machine-id
file:
ln -sfv /var/lib/dbus/machine-id /etc
Many tests are disabled unless both D-Bus Python-1.3.2 and PyGObject-3.46.0 have been installed. They must be run as an unprivileged user from a local session with bus address. To run the standard tests issue make check.
If you want to run the unit regression tests, configure requires additional parameters which expose additional functionality in the binaries that are not intended to be used in a production build of D-Bus. If you would like to run the tests, issue the following commands (for the tests, you don't need to build the docs):
make distclean &&
PYTHON=python3 ./configure --enable-tests \
--enable-asserts \
--disable-doxygen-docs \
--disable-xml-docs &&
make &&
make check
One test, test-autolaunch, is known to fail. There have also been reports that the tests may fail if running inside a Midnight Commander shell. You may get out-of-memory error messages when running the tests. These are normal and can be safely ignored.
Command Explanations
--disable-doxygen-docs
: This switch disables doxygen documentation build and install, if you have doxygen installed. If doxygen is installed, and you wish to build them, remove this parameter.
--disable-xml-docs
: This switch disables html documentation build and install, if you have xmlto installed. If xmlto is installed, and you wish to build them, remove this parameter.
--disable-static
: This switch prevents installation of static versions of the libraries.
--with-systemd{user,system}unitdir=no
: These switches disable installation of systemd units on elogind based systems.
--with-system-socket=/run/dbus/system_bus_socket
: This parameter specifies the location of the system bus socket.
--enable-tests
: Builds extra parts of the code to support all tests. Do not use on a production build.
--enable-embedded-tests
: Builds extra parts of the code to support only unit tests. Do not use on a production build.
--enable-asserts
: Enables debugging code to run assertions for statements normally assumed to be true. This prevents a warning that '--enable-tests
' on its own is only useful for profiling and might not give true results for all tests, but adds its own NOTE that this should not be used in a production build.
Configuring D-Bus
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
D-Bus Session Daemon
To automatically start dbus-daemon when the system is rebooted, install the /etc/rc.d/init.d/dbus
bootscript from the blfs-bootscripts-20231119 package.
make install-dbus
If this is the first time to install D-Bus on the system and you are not operating in a chroot environment, you can immediately start dbus-daemon without rebooting the system:
/etc/init.d/dbus start
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.
-
If you use gdm 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.
-
The examples shown previously use dbus-launch to specify a program to be run. This has the benefit (when also using the --exit-with-x11
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