docs: add instruction to run as service (#61)

README.md

@@ -75,6 +75,8 @@ Then run:
 
 So you can `ssh myserver.com:5202` to ssh to your NAS.
 
+4. If you want to use rathole as service please refer to this [docs](https://github.com/rapiz1/rathole/tree/main/examples/systemd). For windows we recommend NSSM using the guide from [here](https://www.paddingleft.com/2018/05/29/install-nodejs-program-as-windows-service-by-nssm/).
+
 ## Configuration
 `rathole` can automatically determine to run in the server mode or the client mode, according to the content of the configuration file, if only one of `[server]` and `[client]` block is present, like the example in [Quickstart](#Quickstart).
 

examples/systemd/README.md

@@ -0,0 +1,49 @@
+## Systemd Configuration
+
+We provide various systemd examples to make the management of rathole easy. You can find out various services file in
+the current directory.
+
+Here we will try to install server version. Same will apply for client etc.
+
+Before procedding we need to have configuration ready. For that please refer to readme file. Also, @ in filename such as
+`rathole@.service` carries [special meaning](https://superuser.com/questions/393423/the-symbol-and-systemctl-and-vsftpd) to enable multiple instances of rathole. If you are only hosting  one instance then
+feel free to use systemd config file that doesn't use @. Also, whenever we mention systemd config it means file that has *.service extension.
+
+Here is simple instruction to install rathole server.
+
+1. Create a service file:
+
+```bash
+wget https://github.com/rapiz1/rathole/blob/main/examples/systemd/ratholes@.service # download the file
+sudo cp rathole@.service /lib/systemd/system/
+```
+
+2. Create the rathole configuration file we shall call it app1.toml.
+
+```
+sudo mkdir -p /etc/rathole
+# Now create rathole config file called app1 inside /etc/rathole
+```
+
+If you don't want to use /etc/rathole you can tweak the systemd config file
+
+```
+ExecStart=/usr/bin/rathole -s /etc/rathole/%i.toml
+```
+
+_Note_: Don't replace `%i` becase it will be replaced by app1, app2 when we do `systemctl start rathole@app1` in coming
+step.
+
+3. Enable to service so it works automatically when computer is rebooted.
+
+```bash
+sudo systemctl enable ratholes@app1
+```
+
+4. Start the service
+
+```bash
+sudo systemctl enable ratholes@app1
+```
+
+You can use app1, app2 or whatever you like but make sure config file exists.