Add details on volume mapping (#21)

Author: BisonDee

README.md

@@ -29,40 +29,56 @@ This repository contains the relevant Docker builds to run your own node on the
 ### Hardware requirements
 
 We recommend you this configuration to run a node:
+
 - at least 16 GB RAM
 - an SSD drive with at least 100 GB free
 
 ### Troubleshooting
 
 If you encounter problems with your node, please open a [GitHub issue](https://github.com/base-org/node/issues/new/choose) or reach out on our [Discord](https://discord.gg/buildonbase):
+
 - Once you've joined, in the Discord app go to `server menu` > `Linked Roles` > `connect GitHub` and connect your GitHub account so you can gain access to our developer channels
 - Report your issue in `#🛟|node-support`
 
 ### Supported networks
 
 | Ethereum Network | Status |
-|------------------|--------|
+| ---------------- | ------ |
 | Goerli testnet   | ✅     |
 | Mainnet          | 🚧     |
 
 ### Usage
 
 1. Ensure you have an Ethereum Goerli L1 node RPC available (not Base Goerli), and set `OP_NODE_L1_ETH_RPC` (in `docker-compose.yml` if using docker-compose). If running your own L1 node, it needs to be synced before Base will be able to fully sync.
 2. Run:
+
 ```
-docker compose up
+docker compose up --build
 ```
+
 3. You should now be able to `curl` your Base node:
+
 ```
 curl -d '{"id":0,"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest",false]}' \
   -H "Content-Type: application/json" http://localhost:8545
 ```
 
 Note: Some L1 nodes (e.g. Erigon) do not support fetching storage proofs. You can work around this by specifying `--l1.trustrpc` when starting op-node (add it in `op-node-entrypoint.sh` and rebuild the docker image with `docker compose build`.) Do not do this unless you fully trust the L1 node provider.
 
+You can map a local data directory for `op-geth` by adding a volume mapping to the `docker-compose.yaml`:
+
+```yaml
+services:
+  geth: # this is Optimism's geth client
+    ...
+    volumes:
+      - $HOME/data/base:/data
+```
+
 ### Syncing
 
 Sync speed depends on your L1 node, as the majority of the chain is derived from data submitted to the L1. You can check your syncing status using the `optimism_syncStatus` RPC on the `op-node` container. Example:
+
 ```
 echo Latest synced block behind by: \
 $((($( date +%s )-\