Adds post: How to SSH into NixOS VM in GNOME Boxes

Author: dylanmtaylor

posts/2026-03-29-ssh-into-a-nixos-vm-running-in-gnome-boxes.md

@@ -0,0 +1,58 @@
+---
+date: '2026-03-29'
+title: How to SSH into a NixOS VM Running in GNOME Boxes
+description: How to enable SSH on a NixOS guest, set up port forwarding through QEMU's user-mode networking, and copy your SSH keys so you can work from the host terminal.
+---
+## How to SSH into a NixOS VM Running in GNOME Boxes
+
+I spun up a NixOS VM in GNOME Boxes for some quick package development and testing. GNOME Boxes on its own works fine, but I wanted to SSH in from my host so I could use my normal terminal and copy files with `scp`. This turned out to require a few steps that aren't immediately obvious.
+
+### The Problem: User-Mode Networking
+
+GNOME Boxes uses QEMU with user-mode networking by default. The VM gets a NAT'd IP that isn't directly reachable from the host. You need port forwarding to get in.
+
+### Enable SSH on the NixOS Guest
+
+NixOS doesn't enable SSH by default. In the VM, edit `/etc/nixos/configuration.nix` using `sudo nano` to add:
+
+```nix
+services.openssh = {
+  enable = true;
+};
+networking.firewall.allowedTCPPorts = [22];
+```
+
+The firewall line is important as NixOS enables its firewall by default, and without explicitly opening port 22, SSH connections will silently hang even though `sshd` is running.
+
+Then rebuild and switch to the newly built OS environment:
+
+```bash
+sudo nixos-rebuild switch && sudo reboot
+```
+
+### Add Port Forwarding via the QEMU Monitor
+
+In my case, I run GNOME Boxes as a Flatpak, so we have to use `virsh` inside its sandbox. First, find your VM name:
+
+```bash
+flatpak run --command=virsh org.gnome.Boxes -c qemu:///session list --all
+```
+
+Then add a forwarding rule that maps host port 2222 to guest port 22:
+
+```bash
+flatpak run --command=virsh org.gnome.Boxes -c qemu:///session \
+  qemu-monitor-command nixos-unstab --hmp 'hostfwd_add tcp::2222-:22'
+```
+
+Replace `nixos-unstab` with whatever your VM is named.
+
+### Copy Your SSH Keys and Connect
+
+Now copy your keys and SSH in:
+
+```bash
+ssh-copy-id -p 2222 dylan@localhost
+ssh -p 2222 dylan@localhost
+```
+Now you can easily copy files to your guest OS and run any commands you need to from the host's terminal