Add info how to add local user to pihole group

Signed-off-by: yubiuser <[email protected]>

Author: yubiuser

docs/main/post-install.md

@@ -18,3 +18,20 @@ Pi-hole will not be used by the host automatically after installation. To have t
 ```code
 static domain_name_servers=127.0.0.1
 ```
+
+## Adding your local user to the 'pihole' group
+
+Since version 6 Pi-hole uses a new API for authentication. All CLI commands use this API instead of e.g. direct database manipulation. If a password is set for API access, the CLI commands also need to authenticate. To avoid entering the password everytime on CLI, Pi-hole allows users which are members of the 'pihole' group to authenicate without manually entering the password (this can be disabled with setting `webserver.api.cli_pw` to `false`.)
+To add your local user to the 'pihole' group use the following command
+
+For Debian/Ubuntu/Raspberry Pi OS/Armbian/Fedora/CentOS
+
+```code
+sudo usermod -aG pihole $USER
+```
+
+For Alpine
+
+```code
+sudo addgroup pihole $USER
+```