Update index.md with Tailscale persistence instructions and subnet ro…

docs/ugos/install/tailscale/index.md

@@ -2,35 +2,103 @@
 
 ## Instructions
 
-First, you need to log in via SSH:
+### Step 1: Log in via SSH
+
+Open a terminal and connect to your NAS over SSH:
 
 ```sh
 ssh USERNAME@IP
 ```
 
-When asked for a password, use your account password.
+Use your account password when prompted.
+
+---
+
+### Step 2: Install Tailscale
 
-Next, download and install tailscale as described [here](https://tailscale.com/download/linux) with this command:
+Install Tailscale using the official install script:
 
 ```sh
 curl -fsSL https://tailscale.com/install.sh | sh
 ```
 
-Finally, start tailscale with
+---
+
+### Step 3: Start Tailscale
+
+Run the following command to start Tailscale and authenticate your device:
 
 ```sh
 sudo tailscale up
 ```
 
-After starting tailscale, I noticed that the NAS could not access any resources on the internet due to a broken DNS configuration. The cause for this issue is that UGOS uses the file `/etc/resolv.conf` to store the default nameserver but tailscale overrides it when launching.
+You’ll be given a URL to visit in your browser. Follow the link and log into your Tailscale account to connect the device.
 
-To fix it, I had to restart tailscale with [disabled DNS configuration](https://tailscale.com/kb/1241/tailscale-up)
+---
+
+### Step 4: Fix DNS override issue (optional but recommended)
+
+Some users have reported that after starting Tailscale, their NAS cannot reach the internet. This is due to Tailscale overriding `/etc/resolv.conf`, which UGOS relies on for DNS resolution.
+
+To avoid this issue, disable Tailscale's DNS handling:
 
 ```sh
 sudo tailscale down
-sudo tailscale up --accept-dns=false 
+sudo tailscale up --accept-dns=false
+```
+
+---
+
+## Making Tailscale persist after reboot and system updates
+
+By default, Tailscale on UGOS does not retain custom flags or behavior after a reboot or system update. To make sure Tailscale continues to work across reboots, including any advanced options (like subnet routing), you can create a systemd override.
+
+### Step 1: Create a systemd override file
+
+```sh
+sudo mkdir -p /etc/systemd/system/tailscaled.service.d
+sudo nano /etc/systemd/system/tailscaled.service.d/override.conf
+```
+
+Paste the following into the file:
+
+```ini
+[Service]
+ExecStart=
+ExecStart=/usr/sbin/tailscaled --state=/var/lib/tailscale/tailscaled.state --tun=userspace-networking
 ```
 
+Save and exit (`Ctrl+O`, `Enter`, then `Ctrl+X`).
+
+---
+
+### Step 2: Reload systemd and enable the service
+
+```sh
+sudo systemctl daemon-reexec
+sudo systemctl daemon-reload
+sudo systemctl enable tailscaled
+sudo systemctl restart tailscaled
+```
+
+After this, Tailscale will start automatically with your settings every time the system boots.
+
+---
+
+## Advertising a subnet or VLAN
+
+If you want to access other devices on your network through Tailscale by their local IP addresses (such as through a VLAN or LAN subnet), you can advertise that subnet so other devices in your Tailscale network can route traffic through your NAS.
+
+Replace the subnet below with your actual network range:
+
+```sh
+sudo tailscale up --advertise-routes=192.168.100.0/24 --accept-routes --accept-dns=false
+```
+
+Then approve the advertised route in the Tailscale admin panel under **Machines → Routes**.
+
+---
+
 ::: info Credit
-This guide was originally created by [RealMrCr4cker](https://www.reddit.com/user/RealMrCr4cker/) ([Github repo](https://github.com/ln-12/UGOS_scripts/)) and is under an MIT Licence
-:::
+This guide was originally created by [RealMrCr4cker](https://www.reddit.com/user/RealMrCr4cker/) ([Github repo](https://github.com/ln-12/UGOS_scripts/)) and expanded by [spamsgood](https://github.com/spamsgood). It is licensed under the MIT Licence.
+:::