Inconsistency with VNC localdomain configuration

Hello CircleCI community,

I believe I found an inconsistency with certain build images.

We have Selenium tests that connect to Firefox via VNC (tightvncserver Ubuntu package).

In the attached image you can see the difference of .localdomain. When that value is NOT there then Selenium will not be able to connect to Firefox. Around one in four builds do not get the .localdomain part and those builds would fail. From the first glance it looks like some containers are misconfigured or are different.

Here are some examples:

Working “boxes”:

box2 is fine: circleci.com/gh/mozilla/fxa-content-server/5598
box165 is fine: circleci.com/gh/mozilla/fxa-content-server/5599
box154 is fine: circleci.com/gh/mozilla/fxa-content-server/5600
box26 is fine: circleci.com/gh/mozilla/fxa-content-server/5601
box1576 is fine: circleci.com/gh/mozilla/fxa-content-server/5602
box838 is fine: circleci.com/gh/mozilla/fxa-content-server/5603

box183 is not configured properly: https://circleci.com/gh/mozilla/fxa-content-server/5604
It gave me New 'X' desktop is box183:1 which is missing the .localdomain bit.

I checked /etc/hosts in all of these and configuration seems okay.

cat /etc/hosts
127.0.0.1 localhost box183
127.0.0.1 box183.localdomain
151.101.36.162 registry.npmjs.com
151.101.36.162 registry.npmjs.org