Gaming Linux® From Scratch - Version a299

Chapter 3. Shared Dependencies

dbus-1.14.10

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]

Note

Development versions of GLFS may not build or run some packages properly if LFS or dependencies have been updated since the most recent stable versions of the books.

D-Bus Dependencies

Recommended

Xorg Libraries (for dbus-launch program)

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

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, create a symlink to the /var/lib/dbus/machine-id file: 

ln -sfv /var/lib/dbus/machine-id /etc

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 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:

Contents

Installed Programs: dbus-cleanup-sockets, dbus-daemon, dbus-launch, dbus-monitor, dbus-run-session, dbus-send, dbus-test-tool, dbus-update-activation-environment, and dbus-uuidgen
Installed Library: libdbus-1.so
Installed Directories: /etc/dbus-1, /usr/{include,lib}/dbus-1.0, /usr/lib/cmake/DBus1, /usr/share/dbus-1, /usr/share/xml/dbus-1, /usr/share/doc/dbus-1.14.10, and /var/{lib,run}/dbus

Short Descriptions

dbus-cleanup-sockets

is used to clean up leftover sockets in a directory

dbus-daemon

is the D-Bus message bus daemon

dbus-launch

is used to start dbus-daemon from a shell script. It would normally be called from a user's login scripts

dbus-monitor

is used to monitor messages going through a D-Bus message bus

dbus-run-session

starts a process as a new D-Bus session

dbus-send

is used to send a message to a D-Bus message bus

dbus-test-tool

is a D-Bus traffic generator and test tool; it is a multi-purpose tool for debugging and profiling D-Bus

dbus-update-activation-environment

is used to update the environment used for D-Bus session services; it updates the list of environment variables used by dbus-daemon --session when it activates session services without using systemd

dbus-uuidgen

is used to generate a universally unique ID

libdbus-1.so

contains the API functions used by the D-Bus message daemon. D-Bus is first a library that provides one-to-one communication between any two applications; dbus-daemon is an application that uses this library to implement a message bus daemon