Q: How to address the "Your hostname does not resolve to a loopback address" message?
There may be different root causes for the problem above. Please find the subsection that applies to you.
Are you using macOS?
This may be caused by a faulty hostname configuration. You can verify if that's the case by opening the macOS Terminal application:
$ scutil --get HostName
If it prints "HostName: not set" or it prints a hostname made of only numbers or invalid characters, then the issue is confirmed. To address this, you can set the Hostname to _ and let macOS fill it in for you:
$ sudo scutil --set HostName _
Alternatively, you can set your hostname explicitly:
$ sudo scutil --set HostName my-machine
Prompt your password and you should be good to go.
Are you using Windows?
DNS configuration on some flavors of Windows may create an issue with loopback resolution. If you see the "hostname does not resolve to a loopback address" error in the log (typically found at C:\Users\[username]\AppData\Local\Livebook\Logs\Livebook.log), the hosts file on your system might be misconfigured or missing entries. You should check if there's an entry for localhost mapped to 127.0.0.1.
- Open Notepad as an administrator (right-click on Notepad and select 'Run as administrator')
- In Notepad, open the file
C:\Windows\System32\drivers\etc\hosts - Look for a line that reads
127.0.0.1 localhost(it might be commented out). If it's not there, simply add it - Save the file and exit Notepad
- Reboot Windows
Are you using a VPN?
Some VPNs, such as Cisco Any Connect, may block or disable the loopback address. Therefore, you must configure Desktop to use longnames.
-
If you are using Livebook Desktop on Windows, create a file named ".livebookdesktop.bat" in your User Profile folder with the following contents:
set LIVEBOOK_DISTRIBUTION=name set LIVEBOOK_NODE=livebook@127.0.0.1 -
If you are using Livebook Desktop on macOS, create a file named ".livebookdesktop.sh" at your User Home with the following contents:
export LIVEBOOK_DISTRIBUTION=name export LIVEBOOK_NODE=livebook@127.0.0.1 -
If you are using Livebook's CLI or from source, consider using longnames:
$ livebook server --name livebook@127.0.0.1 $ elixir --name livebook@127.0.0.1 -S mix phx.server
Q: How to address the "Protocol 'inet_tcp': register/listen error: no_reg_reply_from_epmd" message?
If you are seeing this message, this means epmd is either not installed, not running, or behind a firewall. Open up the macOS terminal and type epmd directly. The command should succeed or ask for the required permissions if not. If the command is not available, make sure your Erlang installation has all necessary packages.