fixup! [#453] Add documentation for rollup node service

docs/tx_rollup.md

@@ -7,23 +7,37 @@
 
 `proto` variable can hold every active protocol, currently `013-PtJakart` and `014-PtKathma`.
 
-By default, `tezos-tx-rollup-node-$proto.service` will using:
+By default, `tezos-tx-rollup-node-$proto.service` will use:
 * `/var/lib/tezos/.tezos-client` as the `tezos-client` data directory, set in `DATA_DIR`
 * `http://localhost:8732` as the `tezos-node` RPC address, set in `NODE_RPC_ENDPOINT`
 * `127.0.0.1:8472` as the `tezos-tx-rollup-node-$proto` RPC address, set in `ROLLUP_NODE_RPC_ENDPOINT`
 * `observer` as the `tezos-tx-rollup-node-$proto` working mode, set in `ROLLUP_MODE`
 * `rollup` as the rollup alias, set in `ROLLUP_ALIAS`
 
-In order to change defaults, edit `/etc/default/tezos-tx-rollup-node-$proto` file and restart the service.
-
 At first you should originate rollup with the provided alias for some implicit account:
 ```
-sudo -u tezos tezos-client originate tx rollup ${ROLLUP_ALIAS} from ${IMPLICIT_ACCOUNT_ALIAS}
+sudo -u tezos tezos-client originate tx rollup <ROLLUP_ALIAS> from <IMPLICIT_ACCOUNT_ALIAS>
 ```
 
 After that, with the active `tezos-node` service available with the provided uri, run the following command
 ```
 systemctl start tezos-tx-rollup-node-$proto.service
 ```
 
+In order to change the defaults, open `/etc/default/tezos-tx-rollup-node-$proto` and modify the variables:
+
+```
+DATA_DIR="/var/lib/tezos/.tezos-client"
+NODE_RPC_ENDPOINT="http://localhost:8732"
+ROLLUP_NODE_RPC_ENDPOINT="127.0.0.1:8472"
+ROLLUP_MODE="operator"
+ROLLUP_ALIAS="custom-rollup"
+```
+
+Save and close the editor, restart the service:
+
+```
+sudo systemctl restart tezos-tx-rollup-node-$proto.service
+```
+
 For futher details, see [the documentation](http://tezos.gitlab.io/active/transaction_rollups.html).