Add post on non-standard ssh port for a nix build host

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

@@ -0,0 +1,30 @@
+---
+title: How to use a non-default ssh port for a Nix distributed build host
+date: 2022-11-01
+tags: [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`.
+```nix
+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 = [ ];
+}];
+```