Need help getting started

[ovizii]

So I followed the https://docs.lunar.dev/mcpx/get_started and basically did this:

mkdir config

Then realized the docs were just saying where the files go and that they will be created during setup. I can access the control plane but when adding a server I get permission errors:

mcpx | 2026-01-04T20:22:54.322Z [mcpx] ERROR: Failed to create target server memory component="ControlPlaneService" error={"errorName":"Error","errorMessage":"Unknown error ({\"errorName\":\"Error\",\"errorMessage\":\"EACCES: permission denied, open '/lunar/packages/mcpx-server/config/mcp.json'\",\"errorStack\":\"Error: EACCES: permission denied, open '/lunar/packages/mcpx-server/config/mcp.json'\\n at Object.writeFileSync (node:fs:2426:20)\\n at ServerConfigManager.writeTargetServers (file:///lunar/packages/mcpx-server/dist/services/server-config-manager.js:103:16)\\n at TargetClients.addClient (file:///lunar/packages/mcpx-server/dist/services/target-clients.js:144:34)\\n at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\\n at async ControlPlaneService.addTargetServer (file:///lunar/packages/mcpx-server/dist/services/control-plane-service.js:106:13)\\n at async handleWsEvent (file:///lunar/packages/mcpx-server/dist/server/ws-ui.js:135:36)\"})","errorStack":"Error: Unknown error ({\"errorName\":\"Error\",\"errorMessage\":\"EACCES: permission denied, open '/lunar/packages/mcpx-server/config/mcp.json'\",\"errorStack\":\"Error: EACCES: permission denied, open '/lunar/packages/mcpx-server/config/mcp.json'\\n at Object.writeFileSync (node:fs:2426:20)\\n at ServerConfigManager.writeTargetServers (file:///lunar/packages/mcpx-server/dist/services/server-config-manager.js:103:16)\\n at TargetClients.addClient (file:///lunar/packages/mcpx-server/dist/services/target-clients.js:144:34)\\n at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\\n at async ControlPlaneService.addTargetServer (file:///lunar/packages/mcpx-server/dist/services/control-plane-service.js:106:13)\\n at async handleWsEvent (file:///lunar/packages/mcpx-server/dist/server/ws-ui.js:135:36)\"})\n at makeError (file:///lunar/packages/toolkit-core/dist/data/errors.js:5:16)\n at loggableError (file:///lunar/packages/toolkit-core/dist/logging/errors.js:3:19)\n at ControlPlaneService.addTargetServer (file:///lunar/packages/mcpx-server/dist/services/control-plane-service.js:116:27)\n at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\n at async handleWsEvent (file:///lunar/packages/mcpx-server/dist/server/ws-ui.js:135:36)"} data={"type":"stdio","args":["-y","@modelcontextprotocol/server-memory"],"command":"npx","icon":"#303952","name":"memory"}

I have successfully mounted the created directory as a volume. Since I ran this container as root the folder permissions are basically root:root - what is the user ID which needs read/wriote access to the config folder?

[masonearl]

This is a classic Docker permissions issue! The container is running as a non-root user but trying to write to a directory owned by root.

The Fix

You have a few options:

Option 1: Fix the host directory permissions

# Find what user ID the container runs as (often 1000 or node)
docker exec <container_name> id

# Then on your host, change the config folder ownership
sudo chown -R 1000:1000 ./config

Option 2: Use Docker's user flag

docker run -u $(id -u):$(id -g) -v ./config:/lunar/packages/mcpx-server/config ...

Option 3: Make it world-writable (less secure, but quick)

chmod 777 ./config

Why This Happens

Docker containers often run as a specific user (like node or UID 1000) for security. When you create the config folder on your host as root, the container user can't write to it.

Quick Debug

# Check container user
docker exec <container> whoami
docker exec <container> id

# Check config folder permissions
ls -la ./config

Let me know if one of these solutions works!