Docker Continuously Making Unnecessary SSH Connections to Remote Servers

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1

I’m using Docker Desktop for Mac and utilizing docker context to connect to remote servers via SSH. I then build and deploy services using Docker Compose. Everything seems to work normally, however, recently when I checked the server logs, I noticed that my machine was persistently making SSH connections to the remote server, connecting every few seconds.

root@aaaaaaaaa:~# tail -f /var/log/auth.log | grep Accepted
May 21 06:56:09 aaaaaaaa sshd[168869]: Accepted publickey for root from 111.111.111.111 port 57088 ssh2: ED25519 SHA256:xxxxxxxxxxxxxxxx

When I checked my local machine with pstree, I found that com.docker.build was constantly making SSH connections to the remote servers and executing the docker system dial-stdio command.

pstree -u $USER 06567
-+- 06567 tao com.docker.build
|--= 06609 tao ssh -- law-us docker system dial-stdio
|--= 06632 tao ssh -- shui-us docker system dial-stdio
|--= 06633 tao ssh -- law-us docker system dial-stdio
|--= 07561 tao ssh -- shui-us docker system dial-stdio
...

Interestingly, at this time, I am not even using the context of these servers. My current context is the local system. I’m wondering what could be causing this? How can I prevent these seemingly meaningless connection attempts?

The version of my current setup is:

  • Docker Desktop: 4.19.0 (106363)
  • Docker version:
Client: Docker Engine - Community
 Version:           23.0.2
 API version:       1.42
 Go version:        go1.20.2
 Git commit:        569dd73db1
 Built:             Mon Mar 27 15:44:26 2023
 OS/Arch:           darwin/arm64
 Context:           desktop-linux

Server: Docker Desktop 4.19.0 (106363)
 Engine:
  Version:          23.0.5
  API version:      1.42 (minimum version 1.12)
  Go version:       go1.19.8
  Git commit:       94d3ad6
  Built:            Wed Apr 26 16:17:14 2023
  OS/Arch:          linux/arm64
  Experimental:     false
 containerd:
  Version:          1.6.20
  GitCommit:        2806fc1057397dbaeefbea0e4e17bddfbd388f38
 runc:
  Version:          1.1.5
  GitCommit:        v1.1.5-0-gf19387a
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
2

This is the time when I have to say thank you just for asking a question :slight_smile: It is starting to make sense. There is an old issue:

The last comment that I linked explains an error which is related to too many connections. dial-stdio is a non-documented argument which shouldn’t be called manually and it is proxying the standard io (stdin, stdout, stderr). It is probably required when you run a container and want to execcute a command in it remotely, but I agree, it shouldn’t be there when you don’t even use the context. If there is a good reason why it is running constantly, I don’t know that. My first thought was that it could be some kind of “keep-alived” mechanism, but there is nothing to keep alive in your case unles there is a process that is running and connecting to a remote containr even if you switched to another context in your current terminal session. Is it possible that you have a running process in the background and keeps the SSH connection to the remote context alive? Did you restart your machine or Docker Desktop recently?

3

I’ve just started to see those processes recently and my situation is almost the same as you. I have a few servers on my local network to which I have contexts created to connect to, but I’m not currently using any.

My environment is Win11 with Docker Desktop 4.19.0(106363), engine v23.0.5, compose v2.17.3 and I usually work through WSL2 and those servers are Ubuntu 20.04