Using .local Hostnames

A hostname is a name assigned to a device on a network to more easily distinguish between devices instead of using a string of numbers (IP addresses). IP addresses may also be dynamically assigned, making it difficult to consistently reference the same device.

Hostnames can be resolved on the Flight Room network without using a custom DNS or specifying static IP addresses through the router. All devices connected to the network must be running a Zero Configuration Networking (Zeroconf) service which then allows any device to be referenced by adding .local to its hostname.

Each device should have a unique hostname!

Example

One computer uses the hostname hal and another uses the hostname marvin. If both run a Zeroconf service and are on the same network, then hal contacts marvin using the address marvin.local, e.g.

$ ping marvin.local
$ ssh username@marvin.local

Zeroconf and ROS

Using the .local hostname also works with ROS. On Ubuntu, specify marvin as the ROS Master with

$ export ROS_MASTER_URI = http://marvin.local:11311

and specify the computer’s ROS hostname using

$ export ROS_HOSTNAME = $HOSTNAME.local

Add both commands to a user’s .bashrc file to simplify setup.

Setting up the service

You will need administrator privileges if the service is not already installed.

Ubuntu 16.04 / 18.04

A standard installation of Ubuntu will already have a Zeroconf service running, called avahi. Check the status by running service avahi-daemon status in a terminal.

$ service avahi-daemon status
● avahi-daemon.service - Avahi mDNS/DNS-SD Stack
   Loaded: loaded (/lib/systemd/system/avahi-daemon.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2018-08-28 10:09:34 PDT; 53min ago
 Main PID: 1773 (avahi-daemon)
   Status: "avahi-daemon 0.7 starting up."
    Tasks: 2 (limit: 4915)
   CGroup: /system.slice/avahi-daemon.service
           ├─1773 avahi-daemon: running [msladam.local]
           └─1784 avahi-daemon: chroot helper

Otherwise, the package is available in the standard Ubuntu repositories and is installed (or updated) with sudo apt-get install avahi-daemon. A simple check of the service is running

$ ping $HOSTNAME.local

and making sure the address resolves successfully. If the the hostname does not resolve, try the following:

1. Install the avahi packages:

   sudo apt-get install avahi-daemon avahi-dnsconfd avahi-discover avahi-utils
   

2. Install libnss-mdns:

   sudo apt-get install libnss-mdns
   

3. Check that /etc/nsswitch.conf has the following line:

   hosts:    files mdns4_minimal dns [NOTFOUND=return] mdns4
   

Restart avahi with sudo service avahi-daemon restart and try resolving .local hostnames.

Windows 10

Some applications ship with a Zeroconf service called bounjour including Skype and iTunes. Otherwise, the easiest way to install bounjour is to install iTunes. If you don’t want to install iTunes, download the iTunes installer and extract it using 7-Zip or WinRAR. There should be a separate bonjour installer in the extracted files.

Check the service by running

> ping %COMPUTERNAME%.local

in a command prompt.

Changing hostnames

For Ubuntu
For Windows

Resources

ROS Network Setup