Cannot ping my local machine I have just updated my Mac to macOS Sierra 10.12. My hostname is ninjaPixels-Macbook-Pro and if I run:

ping ninjaPixels-Macbook-Pro.local 
or ping ninjaPixels-Macbook-Pro 

I get an error of unknown host.

host ninjaPixels-Macbook-Pro.local returns the error: Host ninjaPixels-Macbook-Pro.local not found: 3(NXDOMAIN)

This is an issue as part of our codebase at work needs to run the following python: socket.gethostbyname(socket.gethostname()) and it fails because my computer seems to have forgotten who it is.

I can successfully run ping localhost and ping 127.0.0.1

I’ve tried the following:


Rebooting.
Switching off the Firewall.
Changing my local hostname, using System Preferences > Sharing > Edit.
sudo killall -HUP mDNSResponder
dscacheutil -flushcache
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist
sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist
Assuming the Firewall is turned off, then in order to ping $HOSTNAME, there has to be some form of sharing or service enabled in System Preferences > Sharing, or add an entry to the /etc/hosts file, depending on how/what you're trying to access by $HOSTNAME. Example, 127.0.0.1 computer_name where computer_name is what's reported by echo $HOSTNAME or in lieu of 127.0.0.1 the actual IP Address of the Network Adapter on your system.