Using Tailscale on Azure App Service

Azure App Service is a popular cloud-hosting platform for running applications without managing servers yourself. However, it can be difficult to use Tailscale on Azure App Service, since it doesn't provide a /dev/net/tun device that Tailscale needs.

You can use Tailscale's userspace networking mode to connect your apps to your Tailscale network.

Step 1: Generate an auth key to authenticate your Azure App Service apps

First, we'll generate an auth key to allow Azure to authenticate our app to join our network.

Open the Keys page of the admin console and select Generate auth key. We recommend using an ephemeral key for this purpose, since it will automatically clean up devices after they shut down.

Next, navigate to the Azure Portal and then the Configuration page for your app. For Config Var, create a variable named TAILSCALE_AUTHKEY, with the tskey-<key> value you just created.

Step 2: Configure your Dockerfile to install Tailscale

We recommend using a multistage Dockerfile where the first stage builds your application, and the second stage pulls application code and Tailscale into the final image to be uploaded to Azure.

Create a Dockerfile at the root of your app. In that Dockerfile add something like:

FROM golang:1.16.2-alpine3.13 as builder
WORKDIR /app
COPY . ./
# This is where one could build the application code as well.

FROM alpine:latest
RUN apk update && apk add ca-certificates bash sudo && rm -rf /var/cache/apk/*

# Azure allows SSH access to the container. This isn't needed for Tailscale to
# operate, but is really useful for debugging the application.
RUN apk add openssh openssh-keygen && echo "root:Docker!" | chpasswd
RUN apk add netcat-openbsd
RUN mkdir -p /etc/ssh
COPY sshd_config /etc/ssh/
EXPOSE 80 2222

# Copy binary to production image.
COPY --from=builder /app/start.sh /app/start.sh

# Copy Tailscale binaries from the tailscale image on Docker Hub.
COPY --from=docker.io/tailscale/tailscale:stable /usr/local/bin/tailscaled /app/tailscaled
COPY --from=docker.io/tailscale/tailscale:stable /usr/local/bin/tailscale /app/tailscale
RUN mkdir -p /var/run/tailscale /var/cache/tailscale /var/lib/tailscale

# Run on container startup.
CMD ["/app/start.sh"]

The Dockerfile specifies /app/start.sh as the initial process to run. This script needs to bring Tailscale up and then start the application binary. Use the TAILSCALE_AUTHKEY variable defined earlier when you bring Tailscale up.

Then, create a file named start.sh at the root of your app:

#!/bin/sh

/usr/bin/ssh-keygen -A
mkdir -p /var/run/sshd
/usr/sbin/sshd

/app/tailscaled --tun=userspace-networking --socks5-server=localhost:1055 &
/app/tailscale up --authkey=${TAILSCALE_AUTHKEY} --hostname=azure-app
echo Tailscale started
ALL_PROXY=socks5://localhost:1055/ /app/my-app

Done! The next time your Azure app deploys, it should be able to connect to your private Tailscale network.

Remove ephemeral nodes from a tailnet

When an ephemeral node goes offline, it is automatically removed from your tailnet. You can also control ephemeral node removal using the tailscale logout command to either manually force the removal or incorporate the command into the tailscaled Tailscale daemon. For more information, see Ephemeral nodes.