Saturday, July 09, 2022

Tribblix and static networking on AWS

I've just made available the m27 AMIs for Tribblix. As usual, these are just available in London (eu-west-2).

One thing I've noticed repeatedly while running illumos on AWS is that network stability isn't great. The instance will occasionally drop off the network and stubbornly refuse to reclaim its IP address even if you reboot it. It's not just Tribblix, I run a whole lot of OmniOS on AWS and that does the same thing.

The problem appears to be related to DHCP not being able to pick up the address (even though I can see it ending out the correct requests and getting what look like legitimate responses).

So what I do is convert the running instance from using NWAM and being a DHCP client to having statically configured networking. On first boot it needs to use DHCP, because it cannot know what its IP address and network configuration should be until it's booted up once and used DHCP to get the details. But it's really extremely rare to take an AWS instance and change its networking - you would simply build new instances rather than modifying existing ones - so changing it to static is fine, and eliminates any possibility of DHCP failures messing you up in future.

In the past I've always done this manually, but now there's a much easier way if you're using m27 or later:

zap staticnet

will show you what the system will do, just as a sanity check, and then

zap staticnet -y

will implement the change.

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