📝 Add LMDB permission troubleshooting section to README

README.md

@@ -217,6 +217,7 @@ WorkingDirectory=/home/wowexplorer/onion-wownero-blockchain-explorer-themefork/b
 
 Type=simple
 ExecStart=/home/wowexplorer/onion-wownero-blockchain-explorer-themefork/build/xmrblocks \
+    -b /path/to/.wownero/lmdb \
     --daemon-url=http://127.0.0.1:34568 \
     --enable-json-api \
     --enable-autorefresh-option \
@@ -226,16 +227,81 @@ ExecStart=/home/wowexplorer/onion-wownero-blockchain-explorer-themefork/build/xm
 Restart=always
 RestartSec=10
 
-# Hardening
-NoNewPrivileges=true
-ProtectSystem=strict
-ProtectHome=read-only
-ReadWritePaths=/home/wowexplorer/.wownero
-
 [Install]
 WantedBy=multi-user.target
 ```
 
+### ⚠️ LMDB Permissions (Important!)
+
+If your blockchain LMDB is owned by a different user (e.g., `jw` runs wownerod but `wowexplorer` runs the explorer), you need to grant access. **LMDB requires write access to the directory** for memory-mapping even for read-only access.
+
+#### Option 1: Use ACLs (Recommended)
+
+```bash
+# Install ACL tools
+sudo apt install acl
+
+# Grant wowexplorer access to traverse to the lmdb directory
+sudo setfacl -m u:wowexplorer:rx /home/jw
+sudo setfacl -m u:wowexplorer:rx /home/jw/.wownero
+
+# Grant rwx on the lmdb directory (required for LMDB memory-mapping)
+sudo setfacl -m u:wowexplorer:rwx /home/jw/.wownero/lmdb
+
+# Grant rw on the database files
+sudo setfacl -m u:wowexplorer:rw /home/jw/.wownero/lmdb/data.mdb
+sudo setfacl -m u:wowexplorer:rw /home/jw/.wownero/lmdb/lock.mdb
+
+# Verify permissions
+getfacl /home/jw/.wownero/lmdb/
+```
+
+#### Option 2: Add user to group
+
+```bash
+# Add wowexplorer to the jw group
+sudo usermod -aG jw wowexplorer
+
+# Set directory permissions
+chmod 711 /home/jw
+chmod 750 /home/jw/.wownero
+chmod 770 /home/jw/.wownero/lmdb
+chmod 660 /home/jw/.wownero/lmdb/*
+
+# Note: Group changes require service restart or reboot to take effect
+sudo systemctl daemon-reexec
+sudo systemctl restart wowexplorer
+```
+
+#### Option 3: Run as the same user
+
+Simply run the explorer as the same user that owns the blockchain:
+
+```ini
+User=jw
+Group=jw
+```
+
+### Troubleshooting LMDB Permission Errors
+
+If you see `Failed to open lmdb environment: Permission denied` errors:
+
+1. **ACLs are most reliable** - Group membership changes aren't picked up by systemd immediately
+2. **LMDB needs write access** - Even for "read-only" access, LMDB needs to write lock files
+3. **Check the full path** - Every directory from `/` to the lmdb folder needs execute permission
+4. **Verify with sudo** - Test access manually: `sudo -u wowexplorer ls -la /path/to/.wownero/lmdb/`
+
+Quick fix with ACLs:
+```bash
+sudo apt install acl
+sudo setfacl -m u:wowexplorer:rx /home/jw
+sudo setfacl -m u:wowexplorer:rx /home/jw/.wownero  
+sudo setfacl -m u:wowexplorer:rwx /home/jw/.wownero/lmdb
+sudo setfacl -m u:wowexplorer:rw /home/jw/.wownero/lmdb/data.mdb
+sudo setfacl -m u:wowexplorer:rw /home/jw/.wownero/lmdb/lock.mdb
+sudo systemctl restart wowexplorer
+```
+
 ### 4. Enable and start the service
 
 ```bash