Set MCP secret in Docker engine

gtp95 · January 20, 2026, 9:26pm

Greetings,

I installed the MCP toolkit on a headless machine running Docker engine (so no Docker Desktop) as explained here. I added the google-maps-comprehensive server, and I now need to add an API key for that. However, I failed so far:

$ docker mcp secret set GOOGLE_MAPS_API_KEY=my_api_key
Post "http://localhost/secrets": dial unix /root/.docker/desktop/jfs.sock: connect: no such file or directory

Note that, to avoid typing sudo docker every time, I aliased docker to sudo docker, but I don’t think this matters here. I know you can give permission to your user to run it without sudo, but this way seems to work just as well without requiring a relogin.

Any idea how I can fix this?
Thank you for your help,

GTP

Edit: her’s some more information

$ docker info                                                                                                                                                          [13/1857]
Client: Docker Engine - Community                                                                                                                                                           
 Version:    29.1.5                                                                                                                                                                         
 Context:    default                                                                                                                                                                        
 Debug Mode: false                                                                                                                                                                          
 Plugins:                                                                                                                                                                                   
  buildx: Docker Buildx (Docker Inc.)                                                                                                                                                       
    Version:  v0.30.1                                                                                                                                                                       
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx                                                                                                                                 
  compose: Docker Compose (Docker Inc.)                                                                                                                                                     
    Version:  v5.0.1                                                                                                                                                                        
    Path:     /usr/libexec/docker/cli-plugins/docker-compose                                                                                                                                
  mcp: Docker MCP Plugin (Docker Inc.)                                                                                                                                                      
    Version:  6c7ffeea484ed3e301cd20eb6b5b38c162895f33                                                                                                                                      
    Path:     /usr/libexec/docker/cli-plugins/docker-mcp                                      

Server:                                        
 Containers: 1                                 
  Running: 0                                   
  Paused: 0                                    
  Stopped: 1                                   
 Images: 3                                     
 Server Version: 29.1.5                        
 Storage Driver: overlayfs                     
  driver-type: io.containerd.snapshotter.v1                                                   
 Logging Driver: json-file                     
 Cgroup Driver: systemd                        
 Cgroup Version: 2                             
 Plugins:                                      
  Volume: local                                
  Network: bridge host ipvlan macvlan null overlay                                            
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog                    
 CDI spec directories:                         
  /etc/cdi                                     
  /var/run/cdi                                 
 Swarm: inactive                               
 Runtimes: io.containerd.runc.v2 runc          
 Default Runtime: runc                         
 Init Binary: docker-init                      
 containerd version: dea7da592f5d1d2b7755e3a161be07f43fad8f75                                 
 runc version: v1.3.4-0-gd6d73eb8              
 init version: de40ad0                         
 Security Options:                             
  apparmor                                     
  seccomp                                      
   Profile: builtin                            
  cgroupns                                     
 Kernel Version: 6.8.0-1041-oracle             
 Operating System: Ubuntu 22.04.5 LTS          
 OSType: linux                                 
 Architecture: x86_64                          
 CPUs: 2              
 Total Memory: 956.7MiB                        
 Name: irc                                     
 ID: 8e7cad3e-6f19-4dbb-8c68-b0f812290f2b      
 Docker Root Dir: /var/lib/docker              
 Debug Mode: false                             
 Experimental: false                           
 Insecure Registries:                          
  ::1/128                                      
  127.0.0.0/8                                  
 Live Restore Enabled: false                   
 Firewall Backend: iptables

rimelek · January 21, 2026, 8:53am

docker mcp secret --help

says

Available Commands:
  ls          List all secret names in Docker Desktop's secret store
  rm          Remove secrets from Docker Desktop's secret store
  set         Set a secret in Docker Desktop's secret store

So all commands are for Docker Desktop. That seems to be one limitation for the mcp command with Docker Engine.

I also found a discussion about this where users shared some workarounds. You could check if that helps. Following some links I also found this comment:

https://github.com/docker/mcp-gateway/pull/149#issuecomment-3404851111

So it looks like this will be supported in the future.

gtp95 · January 21, 2026, 4:56pm

Hello rimelek,

A couple of quick searches on this forum didn’t turn up the discussion you are referring to, would you be so kind to share a link to it?
Thank your for your help,

GTP

rimelek · January 21, 2026, 11:11pm

Oh, sorry, I was sure I added it in my previous post, but somehow I didn’t.

But I see you already found it and referred to it in your new ticket:

github.com/docker/mcp-gateway

Set MCP secret in Docker engine

opened 08:22PM - 21 Jan 26 UTC

GTP95

Greetings, I installed the MCP toolkit on a headless machine running Docker eng…ine (so no Docker Desktop) as explained [here](https://forums.docker.com/t/mcp-toolkit-in-docker-engine-on-linux/150888). I added the google-maps-comprehensive server, and I now need to add an API key for that. However, I failed so far: ``` $ docker mcp secret set GOOGLE_MAPS_API_KEY=my_api_key Post "http://localhost/secrets": dial unix /root/.docker/desktop/jfs.sock: connect: no such file or directory ``` Note that, to avoid typing `sudo docker` every time, I aliased `docker` to `sudo docker`, but I don’t think this matters here. I know you can give permission to your user to run it without sudo, but this way seems to work just as well without requiring a relogin. It seems to me that the issue here is that the MCP toolkit is assuming a Docker Desktop installation. Any idea how I can fix or work around this? Thank you for your help, GTP Edit: this seems to be related to issue #119 , where another user shows an example of a configuration file to work around the problem. But it's not clear to me where I should place that file, and if it needs to have a specific name.

gtp95 · January 22, 2026, 5:12pm

Thank you for the link. At the end of that discussion, there’s the suggestion of using a file like this:

"mcp-gateway": {
"command": "docker",
"args": [
"mcp",
"gateway",
"run",
"--secrets=/home/myuser/.config/Code/User/.env"
],
"env": {
"GITHUB_PERSONAL_ACCESS_TOKEN": "github_pat_12BCB6CMQ0aU2dcHF6BBQX_"
}
}

But it isn’t clear to me where I should put it and how should the file called. Looking at other discussions online, I tried looking on my machine for a file named mcp.json, but there’s no file with that name on my system. Could you please halp with this?
Thank you again,

GTP

meyay · January 22, 2026, 5:30pm

In your mcp client on the host. Only you can tell us what mcp client you want to give access to the tools registered in the mcp gateway.

gtp95 · January 22, 2026, 9:50pm

Thank you for pointing me to the right direction. I’m trying to set up Gemini CLI, so, after looking at the example provided here, this is my full settings.json file for Gemini CLI:

{
  "security": {
    "auth": {
      "selectedType": "oauth-personal"
    }
  },
   "mcpServers": {
    "Maps": {
     "command": "docker",
       "args": ["mcp", "gateway", "run", "--secrets=/home/ubuntu/gta/.env"],
       "env": {"GOOGLE_MAPS_API_KEY": "my_api_key"}
    }
    }
}

I’ve also enabled MCP use for Gemini with $ docker mcp client connect --global gemini. Unfortunately, when I start Gemini CLI I get Error during discovery for MCP server 'Maps': MCP error -32000: Connection closed.
Any ideas on how I could fix this?

Edit: /home/ubuntu/gta/.env contains GOOGLE_MAPS_API_KEY=my_api_key

meyay · January 22, 2026, 10:01pm

Just to be sure: Is the user ubuntu allowed to execute docker commands on your host?

gtp95 · January 23, 2026, 10:10pm

That was indeed the problem, after adding my user to the docker group it seems to work. Thank you!

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