#### Beyond Linux® From Scratch (System V Edition) - Version 12.3

### Chapter 12. System Utilities

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# dbus-1.16.0

## 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 12.3 platform.

### Package Information

- Download (HTTP): https://dbus.freedesktop.org/releases/dbus/dbus-1.16.0.tar.xz

- Download MD5 sum: 66bfcf1f42d4ebc634ca558d14335e92

- Download size: 1.3 MB

- Estimated disk space required: 110 MB (add 6 MB for tests)

- Estimated build time: 0.2 SBU (add 0.4 SBU for tests)

### D-Bus Dependencies

#### Recommended

Xorg Libraries (for dbus-launch program)

#### Optional

For the tests: D-Bus Python-1.3.2, PyGObject-3.50.0, and Valgrind-3.24.0; for documentation: Doxygen-1.13.2, xmlto-0.0.29, Ducktype, and Yelp Tools

## Installation of D-Bus

Install D-Bus by running the following commands (you may wish to review the meson_options.txt file first and add any additional desired options to the meson setup line below):

    mkdir build &&
    cd    build &&

    meson setup --prefix=/usr          \
                --buildtype=release    \
                --wrap-mode=nofallback \
                -D systemd=disabled    \
                .. &&
    ninja

See below for test instructions.

Now, as the `root` user:

    ninja 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-255.17, create a symlink to the `/var/lib/dbus/machine-id` file:

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

Finally, still as the `root` user, rename the documentation directory (it only exists if the optional dependencies are satisfied for at least one documentation format) to make it versioned:

    if [ -e /usr/share/doc/dbus ]; then
      rm -rf /usr/share/doc/dbus-1.16.0    &&
      mv -v  /usr/share/doc/dbus{,-1.16.0}
    fi

Many tests are disabled unless both D-Bus Python-1.3.2 and PyGObject-3.50.0 have been installed. They must be run as an unprivileged user from a local session with bus address. To run the standard tests issue ninja test.

If you want to run the unit regression tests, meson 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):

    meson configure -D asserts=true -D intrusive_tests=true &&
    ninja test

## Command Explanations

`--wrap-mode=nofallback`: This switch prevents meson from using subproject fallbacks for any dependency declarations in the build files, preventing it from downloading any optional dependencies which are not installed on the system.

`-D systemd=disabled`: Don't install systemd support files even if `libsystemd` exists (i.e. the elogind-255.17 package is installed).

`-D intrusive_tests=true`: Builds extra parts of the code to support all tests. Do not use on a production build.

`-D asserts=true`: Enables debugging code to run assertions for statements normally assumed to be true. This prevents a warning that '`-D asserts=true`' 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-20250225 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

## 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-1.16.0, 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

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