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).
This package is known to build and work properly using an LFS-7.5
platform.
Package Information
D-Bus Dependencies
Required
expat-2.1.0
Recommended
Xorg
Libraries (for dbus-launch program)
Optional
For the tests: dbus-glib-0.102, D-Bus
Python-1.2.0, and PyGObject-2.28.6; for the API documentation:
Doxygen-1.8.6; for man pages and XML/HTML
documentation: xmlto-0.0.25
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 /var/run/dbus \
-u 18 -g messagebus -s /bin/false messagebus
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 \
--with-console-auth-dir=/run/console/ \
--without-systemdsystemunitdir \
--disable-systemd \
--disable-static &&
make
See below for test instructions.
Now, as the root user:
make install &&
mv -v /usr/share/doc/dbus /usr/share/doc/dbus-1.8.0
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
D-Bus UUID to avoid warnings when
compiling some packages with the following command as the
root user:
dbus-uuidgen --ensure
The dbus tests cannot be run until after dbus-glib-0.102 has
been installed. They must be run as an unprivileged user from a
local session. Tests fail through ssh. If you want to run only the
unit tests, replace, below, --enable-tests by --enable-embedded-tests, otherwise,
D-Bus Python-1.2.0 has to be installed, before.
The tests require 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. If you would like to run the tests,
issue the following commands:
make distclean &&
./configure --enable-tests --enable-asserts &&
make &&
make check &&
make distclean
If run-test.sh fails,
it can be disabled with the following sed, before running the
commands for the tests:
sed -i -e 's:run-test.sh:$(NULL):g' test/name-test/Makefile.in
Note there has been a report 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
--with-console-auth-dir=/run/console/:
This parameter specifies location of the ConsoleKit auth dir.
--without-systemdsystemunitdir: This
switch prevents installation of systemd unit files.
--disable-systemd: This
switch disables systemd support in D-Bus
--disable-static: This
switch prevents installation of static versions of the libraries.
--enable-tests: Build extra
parts of the code to support all tests. Configure will end with a
NOTE warning about increased size of libraries and decreased
security.
--enable-embedded-tests:
Build extra parts of the code to support only unit tests. Configure
will end with a NOTE warning about increased size of libraries and
decreased security.
--enable-asserts: Enable
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 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-20140301 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.
-
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.
-
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 be 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.