sudo killall coreaudiod made it so I don't have any sound at all I ran into an issue where my volume buttons on my mac weren't able to adjust the volume of my computer. I sought a solution and someone suggested using sudo killall coreaudiod. Now I have no volume on my computer at all. How do I fix this?
This command will do it:
sudo launchctl stop com.apple.audio.coreaudiod &amp;&amp; sudo launchctl start com.apple.audio.coreaudiod

Details
Martin Strouhal's answer doesn't work for OS X/macOS ≥ 10.12.4 due to removal of com.apple.audio.coreaudiod from system integrity protection's RemovableServices whitelist in /System/Library/Sandbox/com.apple.xpc.launchd.rootless.plist [1].

sudo launchctl unload /System/Library/LaunchDaemons/com.apple.audio.coreaudiod.plist
/System/Library/LaunchDaemons/com.apple.audio.coreaudiod.plist: _
   Operation not permitted while System Integrity Protection is engaged


So instead of unloading the service, we instead just restart it.
Also, the latter command (sudo launchctl start com.apple.audio.coreaudiod) worked to restart the service after I had killed coreaudiod using killall coreaudiod.