Solution to disappear without sound and sound icons in ubuntu

Ubuntu does not have sound and sound icons disappear. Solution: If ubuntu is installed, or after the upgrade, no sound output is found in ubuntu, and only dump output is displayed in the sound settings. You can solve this problem by checking the sound card first: cat/proc/asound/cards check whether there is a sound card-> If nosoundcars is used, it means that the sound card cat/proc/asound/device shows that all ALSA components are reinstalled and the pulseaudio sudo update -grub sudo apt-get remove -- purge alsa-base sudo apt-get remove -- purge pulseaudio sudo apt-get install alsa-base sudo apt-get install pulseaudio sudo alsa force-reload restart now there should be sound, if no sound setting icon is found in indicator, run alt + f2 and enter gnome-volume-control-applet. When dicator appears, this method is feasible, but it is too annoying to do this once when it is not started, therefore, if you run gnome-session-properties and add a new startup Item to it, you can also use synaptic to install indicator-applet-complete and unregister it, log on again and adjust the voice in all the OK command lines: alsamixer PS: many people do not know much about the Linux sound system, ALSA, OSS, PulseAudio, and ESD. Here I can explain my understanding, here are four different terms related to Sound. The first is ALSA (Advance Linux Sound Arichitecture). We can know from Baidu that it is included in linux kernel and provides underlying Sound drivers, it is used to replace the OSS (Open Sound System) and is now the default Sound subsystem. The underlying driver problem is also solved, and audio processing between different applications needs to be solved. The sound service needs to be provided to play an adaptation role. ESD is the GNOME sound server, however, the ESD solution is too complicated and involves decoding and compression .., this will make the entire system very messy, while PulseAudio mainly aims to reduce the complexity of the sound system, provide unified interfaces for applications, and facilitate the development of various sound applications.