Add headless documentation

README.md

@@ -33,6 +33,57 @@ It will install WireGuard (kernel module and tools) on the server, configure it,
 
 Run the script again to add or remove clients!
 
+## Headless install
+
+It's also possible to run the script headless, e.g. without waiting for user input, in an automated manner.
+
+Example usage:
+
+```bash
+AUTO_INSTALL=y ./wireguard-install.sh
+
+# or
+
+export AUTO_INSTALL=y
+./wireguard-install.sh
+```
+
+A default set of variables will then be set, by passing the need for user input.
+
+If you want to customise your installation, you can export them or specify them on the same line, as shown above.
+
+- `APPROVE_INSTALL=y`
+- `APPROVE_IP=y`
+- `APPROVE_NIC=y`
+- `SERVER_WG_NIC=wg0`
+- `SERVER_WG_IPV4=10.66.66.1`
+- `SERVER_WG_IPV6=fd42:42:42::1`
+- `SERVER_PORT=51820`
+- `CLIENT_DNS_1=176.103.130.130`
+- `CLIENT_DNS_2=176.103.130.131`
+- `CLIENT_NAME=client`
+- `CLIENT_DOT_IPV4=2`
+- `CLIENT_DOT_IPV6=2`
+
+If the server is behind NAT, you can specify its endpoint with the `SERVER_PUB_IP` variable. If the endpoint is the public IP address which it is behind, you can use `SERVER_PUB_IP=$(curl ifconfig.co)` (the script will default to this). The endpoint can be an IP or a domain.
+
+Other variables can be set depending on your choice (`SERVER_NIC`). You can search for them in the `installQuestions()` function of the script.
+
+## Headless User Addition
+
+It's also possible to automate the addition of a new user. Here, the key is to provide the (string) value of the `MENU_OPTION` variable along with the remaining mandatory variables before invoking the script.
+
+The following Bash script adds a new user `foo` to an existing WireGuard configuration
+
+```bash
+#!/bin/bash
+export MENU_OPTION="1"
+export CLIENT_NAME="foo"
+export CLIENT_DOT_IPV4="3"
+export CLIENT_DOT_IPV6="3"
+./wireguard-install.sh
+```
+
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