## TL;DR
This error means the tailscaled daemon is stopped: the tailscale command you type is only a client, it talks to the daemon over a local socket, and every client command fails this way when the daemon is not running. On Linux, start the daemon with sudo systemctl enable --now tailscaled, then run sudo tailscale up again. It is not a network, account, or install problem; the background service is down or was never started.

```text
failed to connect to local tailscaled; it doesn't appear to be running (sudo systemctl start tailscaled ?)
```

## Use this when
- Any tailscale command (up, status, ping) fails with failed to connect to local tailscaled
- The message suggests starting tailscaled with systemctl and you are on Linux
- The same failure appears on macOS, Windows, or a snap install, where the daemon runs as an app, a service, or a snap instead

## Not for this skill when
- tailscale status works but shows NeedsLogin. That is an expired session, not a stopped daemon; re-authenticate with tailscale up instead
- The daemon is running and active but nodes cannot reach each other. That is a connectivity or ACL problem, not this one

## Steps

1. Start the daemon on Linux with systemd: sudo systemctl enable --now tailscaled. This starts it now and keeps it enabled across reboots.

Expected: no output, which means success.

2. Confirm it stayed up: systemctl is-active tailscaled.

Expected: active. Anything else means the daemon started and died; go to step 4.

3. Retry the client: sudo tailscale status, then sudo tailscale up if it asks you to log in.

Expected: your node info prints instead of the connect error, and the node comes online.

4. If the service will not stay up, read the log: journalctl -u tailscaled -n 50. The common causes are a missing /dev/net/tun device (containers and LXC guests need the TUN device passed through from the host) or another VPN holding the device.

Expected: the log names the cause instead of the generic client-side connect error.

5. On other platforms, start the equivalent service. macOS: relaunch the Tailscale app; the daemon is a system extension, so approve it under System Settings, Privacy and Security if it is blocked. Windows: start the Tailscale service in services.msc. Snap installs: sudo snap restart tailscale.

Expected: the client commands in step 3 succeed on that platform too.

## Variant phrasings

### tailscaled doesn't appear to be running
The same stopped-daemon failure without the systemctl hint in the text. Start the daemon for your platform (steps 1 and 5), then retry.

### tailscale up failed to connect to local tailscaled
tailscale up is a client command, so it fails like all the others while the daemon is down. The fix order matters: daemon first, up second.

### tailscale daemon not running ubuntu
On Ubuntu the daemon is the tailscaled systemd unit (step 1), or the tailscale snap on snap installs (step 5). Check is-active before reinstalling anything; a reinstall does not fix a service that was simply never started.

## Root cause
Client/daemon split. The socket the CLI dials only exists while tailscaled runs, so a stopped daemon breaks every client command the same way, and the error text points at the daemon because that is the missing piece.

## Edge cases
- On headless servers, authenticate with an auth key when you run tailscale up, since there is no browser to complete the login.
- Do not run tailscale up under a short timeout: it blocks waiting for the browser login, and a timeout kill looks like a new failure.
- In containers and LXC guests, no service restart fixes a missing TUN device; the host has to pass /dev/net/tun through.

## Tool compatibility
Tailscale on Linux (systemd and snap installs), macOS (app with system extension), and Windows (Tailscale service). Applies whenever the tailscaled daemon is installed but not running.

## Related skills
- duplicate node key tailscale: fix the Duplicate node key warning in the admin console: https://vectle.com/skills/skl_qmlicXbtFhGlMME7wMix7w
- tailscale up on a headless server: https://vectle.com/skills/skl_RqENuhopBsY-tKOM-lFSmQ

## Provenance
Built from the Tailscale install docs: https://tailscale.com/kb/1032/install-ubuntu