Unable to Connect to Local Beszel Agent in Docker

[ericukk]

I’m running into issues trying to connect to the local Beszel agent using the Docker setup provided in the getting started guide. Here is the relevant part of the docker-compose.yml I’m using:

services:
  beszel:
    image: henrygd/beszel:latest
    container_name: beszel
    restart: unless-stopped
    extra_hosts:
      - host.docker.internal:host-gateway
    ports:
      - 8090:8090
    volumes:
      - ./beszel_data:/beszel_data

  beszel-agent:
    image: henrygd/beszel-agent:latest
    container_name: beszel-agent
    restart: unless-stopped
    network_mode: host
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    environment:
      PORT: 45876
      KEY: 'redacted'

After running docker compose down && docker compose up -d, the beszel-agent container is listed as “down,” and the logs don’t show any attempts to connect:

docker compose logs -f -n 100
beszel-agent  | 2024/12/31 23:08:27 INFO Root disk mountpoint=/ io=sda
beszel        | 2024/12/31 23:08:28 Server started at http://0.0.0.0:8090
beszel        | ├─ REST API:  http://0.0.0.0:8090/api/
beszel        | └─ Dashboard: http://0.0.0.0:8090/_/
beszel-agent  | 2024/12/31 23:08:27 INFO Detected network interface name=wlan0 sent=24551158 recv=25407343
beszel-agent  | 2024/12/31 23:08:27 INFO Detected network interface name=tailscale0 sent=26720 recv=58350
beszel-agent  | 2024/12/31 23:08:27 INFO Starting SSH server address=:45876

The beszel container is running fine, but I'm unable to figure out why the agent is not connecting. The agent logs don't show much info, and without shell access or nc inside the container, debugging is tricky.

Anyone have suggestions or insights into what might be causing this issue?

Beszel version 0.9.0
Raspberry Pi 4 on NixOS 24.11
cgroup memory is enabled

[henrygd]

Do you see errors on the logs page at /_/#/logs?

Scratch images are nice, but I agree it's annoying to debug something like this with no shell available. Maybe I'll add an :alpine image to make the process easier.

[ericukk]

Thanks for the quick response.
It seems that there was a connection problem when I tried to start it up the first time.

I just tried to compose down and up again but couldn't reproduce, there's only INFO logs of successful http requests.
I'll see if I can copy some tools into the container to try to get more information.

[ericukk]

I believe I've figured out the issue and can now make it work. I recompiled the container using Alpine based on your suggestion, which was really helpful for debugging.

From the container, I could ping host.docker.internal and connect to other ports on my host, but not to 45876. After further debugging, I realized the issue was with the firewall. Once I opened it, everything worked.

I'll investigate why I didn’t need to do that when I tried to replicate on my Fedora setup, but only on NixOS. It might be due to some different default settings.

Thanks a lot for your help. I learned a great deal. Happy new year.

[henrygd]

Interesting, thanks for the update!

I wonder if you would be able to connect from the host using telnet localhost 45876 with the firewall active, or if it's specifically a problem connecting from a container via host.docker.internal.