docs: add customization section in linux.md (#7709)

docs/linux.md

@@ -112,6 +112,21 @@ sudo systemctl status ollama
 > https://www.amd.com/en/support/linux-drivers for best support of your Radeon
 > GPU.
 
+## Customizing
+
+To customize the installation of Ollama, you can edit the systemd service file or the environment variables by running:
+
+```
+sudo systemctl edit ollama
+```
+
+Alternatively, create an override file manually in `/etc/systemd/system/ollama.service.d/override.conf`:
+
+```ini
+[Service]
+Environment="OLLAMA_DEBUG=1"
+```
+
 ## Updating
 
 Update Ollama by running the install script again: