blog/content/posts/2022/11/ssh-port-distributed-builds.md

title	date	tags
How to use a non-default ssh port for a Nix distributed build host	2022-11-01	nix

I wanted to host my ssh server on a different port than the default 22, this allows me to skip on some spam in the logs, as the default port gets scanned quite often. By changing that on the server I broke distributing my nix builds, as they were using the default port as well. It took me a while to figure out how to configure the port the builder would use so I thought I would share here.

Here's an example of a client-side configuration - using a build server buildHostName with a user named nix-builder, connecting via ssh to port 1234.

programs.ssh.extraConfig = ''
    Host buildHostName
	HostName buildHostName
	Port 1234
	StrictHostKeyChecking=accept-new
'';

nix.buildMachines = [{
    hostName = "buildHostName";
    sshUser = "nix-builder";
    sshKey = "/path/to/key";
    systems = [ "x86_64-linux" ];
    maxJobs = 2;
    speedFactor = 2;
    supportedFeatures = [ "kvm" ];
    mandatoryFeatures = [ ];
}];