项目场景：

对于systemd系统来说，DBUS是必不可少的工具，它是进程间通讯的桥梁。

问题描述

当我们在WSL2中安装QQ音乐的时候，打开崩溃，具体的提示错误是：Failed to connect to the bus: Failed to connect to socket /run/user/1000/bus: No such file or directory

意思就是没有/run/user/1000/bus这个文件，我们去这个目录下面确实没找到这个文件。

ls /run/user/1000/
dbus-1  gnupg  pk-debconf-socket  pulse  snapd-session-agent.socket  systemd  wayland-0  wayland-0.lock
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简单解释下：
1000是除了root用户外你创建的第一个用户ID，第二个ID是1001。

有些软件可能能够运行，但是像QQ音乐Linux版，没有这个文件就直接崩溃或不出声音。

原因分析：

DBUS简单理解就是用于处理进程间通讯的桥梁，用来在不同的Applications中相互传递消息。它的效率很高，很多发行版中都集成了。

有些Applications依赖这个东西，如果没有的话就不能正常运行。废话不多说，由于DBUS很复杂，有兴趣的可以自行搜索学习下。这里，我只说解决方法。

解决方案：

其实是缺少了一个包，我们搜索dbus看下就明白了。

dpkg -l | grep dbus
ii  at-spi2-core                         2.44.0-3                                amd64        Assistive Technology Service Provider Interface (dbus core)
ii  dbus                                 1.12.20-2ubuntu4.1                      amd64        simple interprocess messaging system (daemon and utilities)
ii  dbus-x11                             1.12.20-2ubuntu4.1                      amd64        simple interprocess messaging system (X11 deps)
ii  libdbus-1-3:amd64                    1.12.20-2ubuntu4.1                      amd64        simple interprocess messaging system (library)
ii  libdbusmenu-glib4:amd64              16.04.1+18.10.20180917-0ubuntu8         amd64        library for passing menus over DBus
ii  libdbusmenu-gtk3-4:amd64             16.04.1+18.10.20180917-0ubuntu8         amd64        library for passing menus over DBus - GTK+ version
ii  libnet-dbus-perl                     1.2.0-1build3                           amd64        Perl extension for the DBus bindings
ii  python3-dbus                         1.2.18-3build1                          amd64        simple interprocess messaging system (Python 3 interface)
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这里少了一个包dbus-user-session，装上这个包就不会报错了。

sudo apt install dbus-user-session
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我们看下这个包的描述信息，重点看Description:

apt info dbus-user-session

Package: dbus-user-session
Version: 1.12.20-2ubuntu4.1
Priority: optional
Section: admin
Source: dbus
Origin: Ubuntu
Maintainer: Ubuntu Developers <[email protected]>
Original-Maintainer: Utopia Maintenance Team <[email protected]>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 133 kB
Provides: dbus-session-bus, default-dbus-session-bus
Depends: dbus (>= 1.12.20-2ubuntu4.1), libpam-systemd, systemd
Recommends: systemd-sysv
Breaks: dbus-x11 (<< 1.9.10-2~), policykit-1 (<< 0.105-12~), udisks2 (<< 2.1.5-2~)
Homepage: https://dbus.freedesktop.org/
Task: server-minimal, print-server, ubuntu-desktop-minimal, ubuntu-desktop, cloud-image, ubuntu-desktop-raspi, ubuntu-desktop-raspi, server, ubuntu-server-raspi, ubuntu-server-raspi, kubuntu-desktop, xubuntu-core, xubuntu-desktop, lubuntu-desktop, ubuntustudio-desktop-core, ubuntustudio-desktop, ubuntukylin-desktop, ubuntu-mate-core, ubuntu-mate-desktop, ubuntu-budgie-desktop, ubuntu-budgie-desktop-raspi, ubuntu-budgie-desktop-raspi
Download-Size: 9442 B
APT-Manual-Installed: yes
APT-Sources: http://mirrors.aliyun.com/ubuntu jammy-security/main amd64 Packages
Description: simple interprocess messaging system (systemd --user integration)
 D-Bus is a message bus, used for sending messages between applications.
 Conceptually, it fits somewhere in between raw sockets and CORBA in
 terms of complexity.
 .
 On systemd systems, this package opts in to the session model in which
 a user's session starts the first time they log in, and does not end
 until all their login sessions have ended. This model merges all
 parallel non-graphical login sessions (text mode, ssh, cron, etc.), and up
 to one graphical session, into a single "user-session" or "super-session"
 within which all background D-Bus services are shared.
 .
 Multiple graphical sessions per user are not currently supported in this
 mode; as a result, it is particularly suitable for gdm, which responds to
 requests to open a parallel graphical session by switching to the existing
 graphical session and unlocking it.
 .
 To retain dbus' traditional session semantics, in which login sessions
 are artificially isolated from each other, remove this package and install
 dbus-x11 instead.
 .
 See the dbus package description for more information about D-Bus in general.

N: There is 1 additional record. Please use the '-a' switch to see it
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简单解释下：
意思就是这个东西是用来进程间通信的消息库，这个是依赖systemd系统的，在用户第一次登录进来开始一个会话，直到所有的登录会话都结束它才结束。

总结：

对于必须依赖这个包的程序有用，能正常运行的可以不装。