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SSH remote management on the live ISO

The routerd live ISO does not run an SSH daemon by default. The default posture is closed: only the local and serial consoles are available (tty1, tty2, ttyS0). This keeps passwordless-root access off the network.

For appliances running as hypervisor VMs (Proxmox VE, KVM, etc.) where serial console access is inconvenient, an opt-in SSH mode can be enabled without baking credentials into the ISO image.

Prerequisites​

  • A config disk (labeled ROUTERD_CONFIG or ROUTERD, or passed with routerd.usb=) containing an authorized_keys file.
  • The ability to set kernel parameters at boot (edit the GRUB entry or set the VM's kernel arguments from the hypervisor).

Enabling SSH​

Step 1 — place your public key on the config disk​

On the config disk (e.g. the Proxmox VM disk that holds router.yaml), create the authorized_keys file inside the routerd/ directory:

routerd/
  router.yaml
  authorized_keys       ← add this file

The file follows standard OpenSSH authorized_keys format:

ssh-ed25519 AAAA...yourkey... user@host

Host-specific key files are also supported (looked up before the generic file):

routerd/hosts/<hostname>/authorized_keys
routerd/hosts/<mac>/authorized_keys   (colon-separated or compact lowercase)

Step 2 — boot with routerd.ssh=1​

Add the routerd.ssh=1 parameter to the kernel command line.

GRUB (live ISO boot menu — press e to edit):

linux /boot/vmlinuz-lts ... routerd.ssh=1

Proxmox VE — set boot args on the VM:

qm set <vmid> --args "-append routerd.ssh=1"

Or set it once in the VM's GRUB entry so it persists across reboots.

What happens at boot​

  1. live-persistence.sh init mounts the config disk and restores router.yaml.
  2. live-autostart.sh installs dependencies (including openssh if not already present).
  3. live-ssh.sh checks for routerd.ssh=1 on the kernel command line.
  4. If the flag is set, it looks for authorized_keys on the mounted config disk.
  5. If found, the key(s) are installed to /root/.ssh/authorized_keys, host keys are generated with ssh-keygen -A, and sshd is started.
  6. If routerd.ssh=1 is set but no authorized_keys file is found, sshd is not started and a warning is logged to /run/routerd/logs/routerd-ssh.log.

Security model​

PropertyValue
Default stateSSH disabled
AuthenticationPublic key only
Password auth for rootPermanently disabled (PasswordAuthentication no)
Root loginPermitRootLogin prohibit-password (key-authenticated only)
Credentials in ISONone — keys come from the config disk at runtime

SSH is only enabled by explicit opt-in and only when credentials have been provided on external media. There is no fallback to password authentication.

Troubleshooting​

sshd did not start:

cat /run/routerd/logs/routerd-ssh.log

Common reasons:

  • routerd.ssh=1 not present on the kernel command line — check /proc/cmdline.
  • Config disk not mounted — check /proc/mounts for /media/routerd-usb.
  • authorized_keys not found at the expected path — live-ssh.sh logs the expected location.

Verify sshd is running:

pgrep -x sshd
ss -tlnp | grep :22

Re-run the SSH setup without rebooting:

/usr/share/routerd/live-ssh.sh

See also​