Action does not seem to work on `ubuntu-slim` runner

[robyn-streetwave]

Using ubuntu-latest works, but ubuntu-slim causes the tailscale status to re-try until it fails.

Extract from workflow file:

    - name: Tailscale
      uses: tailscale/github-action@v4
      with:
        oauth-client-id: ${{ env.DEVOPS_GITHUB_TAILSCALE_TS_OAUTH_CLIENT_ID }}
        audience: ${{ env.DEVOPS_GITHUB_TAILSCALE_TS_AUDIENCE }}
        tags: tag:github-actions
        ping: devops-prod

output partially redacted:

Run tailscale/github-action@v4
  with:
    oauth-client-id: ***
    audience: ***
    tags: tag:github-actions
    ping: devops-prod
    version: 1.94.2
    timeout: 2m
    retry: 5
    use-cache: true

.....

Cache restored successfully
Found Tailscale 1.94.2 in cache: /opt/hostedtoolcache/tailscale/1.94.2/Linux-amd64
▶️ copy tailscale from cache
/usr/bin/sudo cp /opt/hostedtoolcache/tailscale/1.94.2/Linux-amd64/tailscale /usr/local/bin/tailscale
▶️ copy tailscaled from cache
/usr/bin/sudo cp /opt/hostedtoolcache/tailscale/1.94.2/Linux-amd64/tailscaled /usr/local/bin/tailscaled
▶️ chmod tailscale
/usr/bin/sudo chmod +x /usr/local/bin/tailscale
▶️ chmod tailscaled
/usr/bin/sudo chmod +x /usr/local/bin/tailscaled
Starting tailscaled daemon...
Waiting for tailscaled daemon to become ready...
▶️ get tailscale status
/usr/local/bin/tailscale status --json
failed to connect to local tailscaled (which appears to be running as tailscaled, pid 168). Got error: 503 Service Unavailable: no backend
##[debug]Waiting for daemon... (0ms elapsed)
▶️ get tailscale status
/usr/local/bin/tailscale status --json
failed to connect to local tailscaled; it doesn't appear to be running (sudo systemctl start tailscaled ?)
##[debug]Waiting for daemon... (500ms elapsed)
▶️ get tailscale status
/usr/local/bin/tailscale status --json
failed to connect to local tailscaled; it doesn't appear to be running (sudo systemctl start tailscaled ?)
##[debug]Waiting for daemon... (1000ms elapsed)
▶️ get tailscale status
/usr/local/bin/tailscale status --json
failed to connect to local tailscaled; it doesn't appear to be running (sudo systemctl start tailscaled ?)
##[debug]Waiting for daemon... (1500ms elapsed)

[jaxxstorm]

I did a little bit of an investigation into this, and came to the conclusion this fails because ubuntu-slim is a docker like/or containerized environment.

If you try and start tailscaled manually, you see that there's no iptables binary and you can't create a TUN device

Run echo "=== Attempting to start tailscaled manually ==="
=== Attempting to start tailscaled manually ===
Started tailscaled with PID: 619
TPM: error opening: stat /dev/tpmrm0: no such file or directory
2026/04/25 16:12:45 logtail started
2026/04/25 16:12:45 Program starting: v1.96.4-t8cf541dfd-g62bc84ce7, Go 1.26.1: []string{"/usr/local/bin/tailscaled", "--state=/var/lib/tailscale/tailscaled.state", "--socket=/var/run/tailscale/tailscaled.sock"}
2026/04/25 16:12:45 LogID: 814df802a432d767388ba667d1fd12eb3c9910f4f75d803f0028bf9b3b364b07
2026/04/25 16:12:45 logpolicy: using system state directory "/var/lib/tailscale"
2026/04/25 16:12:45 dns: [rc=unknown ret=direct]
2026/04/25 16:12:45 dns: using "direct" mode
2026/04/25 16:12:45 dns: using *dns.directManager
2026/04/25 16:12:45 linuxfw: clear iptables: exec: "iptables": executable file not found in $PATH
2026/04/25 16:12:45 linuxfw: clear ip6tables: exec: "ip6tables": executable file not found in $PATH
2026/04/25 16:12:45 cleanup: list tables: netlink receive: operation not permitted
2026/04/25 16:12:45 dns: inotify: NewDirWatcher: context canceled
2026/04/25 16:12:45 wgengine.NewUserspaceEngine(tun "tailscale0") ...
2026/04/25 16:12:45 Linux kernel version: 6.1.146.1-microsoft-standard
2026/04/25 16:12:45 is CONFIG_TUN enabled in your kernel? `modprobe tun` failed with: 
2026/04/25 16:12:45 tun module not loaded nor found on disk
2026/04/25 16:12:45 wgengine.NewUserspaceEngine(tun "tailscale0") error: tstun.New("tailscale0"): CreateTUN("tailscale0") failed; /dev/net/tun does not exist
2026/04/25 16:12:45 flushing log.
2026/04/25 16:12:45 logger closing down
2026/04/25 16:12:45 getLocalBackend error: createEngine: tstun.New("tailscale0"): CreateTUN("tailscale0") failed; /dev/net/tun does not exist

=== Checking if process is still running ===
  PID TTY          TIME CMD
Process 619 is not running

=== Checking socket ===
ls: cannot access '/var/run/tailscale/tailscaled.sock': No such file or directory
Socket still not created

=== Trying to get status ===
failed to connect to local tailscaled; it doesn't appear to be running (sudo systemctl start tailscaled ?)
Failed to get status

You can update the args if you want to run in userspace mode:

tailscaled-args: --tun=userspace-networking
args: --accept-dns=false

But it will be functionally very limited in usability, because you'll need to configure a SOCKS proxy for all connectivity requirements. As a result, I think we should just document that ubuntu-slim doesn't work and leave it at that