This tutorial will explain How to remove and restore the Volume Button from the Indicator Applet in Ubuntu Panel.
How to remove volume Button from the Indicator Applet from ubuntu panel
You can remove volume button from ubuntu panel by removing the package called indicator-sound (A system sound indicator which provides easy control of the PulseAudio sound daemon.)
Open the terminal and run the following command
sudo apt-get remove --purge indicator-sound
Now you need to restart the gnome panel with the following command from your terminal
Restore volume button to system tray
You need to Right-click an empty area of the panel, choose Add to Panel, then drag Indicator Applet to next to the clock in the system tray, or wherever you want to put it instead. The volume button will be restored.
Alt+F2 to open the Run Application app, enter gnome-volume-control-applet click on run button will disappear if you close your terminal session so how to fix this here is the solution
To get it to start automatically from the next reboot, go to System > Preferences > Startup Applications and add it as a new entry with a name “Volume Button”.