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Asked: 2024-09-25T19:29:16+05:30 In:

I’m having trouble getting a Docker Swarm node to join an existing swarm. I’ve tried using the join token provided, but it doesn’t seem to be working. Can anyone suggest what could be causing this issue or any steps I should take to troubleshoot the problem?

I’m caught in a bit of a bind here and could really use some help with Docker Swarm. So, I’ve set up my main swarm manager without any issues, and it’s running smoothly. However, when I try to add a new node to the swarm, it just won’t cooperate. I’ve been using the join token that I got from the manager, but for some reason, my new node just won’t join.

I’ve double-checked the command I’m using to join – it’s definitely the right one, and I’ve made sure I’m using the correct token. The command looks something like this: `docker swarm join –token :`. But when I run it on my new node, I get an error that says it can’t connect to the manager at the specified IP address. To make things even more confusing, I can ping the manager just fine from the new node.

I considered that maybe there was a network issue, but everything seems fine on that front. The nodes are all in the same subnet, and there’s nothing that looks off in the firewall settings. I also verified that both Docker services are running on both nodes. It seems like the new node isn’t even getting to the point of processing the token when trying to join, which makes me think there’s either a network misconfiguration or a Docker setting that’s causing it to fail silently.

Has anyone experienced something similar? Are there any specific logs or settings I should check to get more insight into what’s going wrong? I’ve looked around a bit but haven’t found anything that directly addresses this particular scenario. I’m really stuck here and would appreciate any pointers or troubleshooting steps you might have. Would love to get this new node up and running so I can start testing my application in the swarm environment. Thanks in advance for any help you can offer!

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    2 Answers


    1. It sounds like you’re in a tricky situation with Docker Swarm! Here are a few things you might want to check out:

      • Check the IP and Port: Make sure you’re using the right IP address and port for your swarm manager. Typically, the port should be 2377. So your command should look like this: docker swarm join --token <token> <manager-ip>:2377.
      • Firewall Rules: Even if everything seems fine, firewalls can be sneaky! Double-check that the firewall on the manager allows traffic on port 2377 and also the ports used for overlay networking (usually 7946 and 4789).
      • Docker Version: Ensure you have compatible versions of Docker on both nodes. Sometimes different versions can cause issues with communication.
      • Swarm Status: Check the status of your swarm. Run docker node ls on your manager to see if there’s anything suspicious.
      • Docker Logs: Looking at the logs on both the manager and the new node can provide valuable clues. You can find the logs typically at /var/log/docker.log or use docker service logs if you’re running services.
      • Network Configuration: Verify that both nodes are indeed in the same subnet as you mentioned. Run ifconfig or ip a on both machines to see their network settings.

      If all else fails, you can try restarting Docker on both nodes or even rebooting the systems. Sometimes a fresh start can resolve weird connectivity issues!

      Good luck, and happy Docker Swarming!



    2. It sounds like you’re experiencing a common issue when trying to add a new node to your Docker Swarm. Since you can ping the manager from the new node, we can likely rule out network connectivity issues. One key area to investigate is whether you’re using the correct IP address and port for the manager node. Ensure you’re using the actual IP address of the manager (not a hostname or an incorrect IP) and that the port is indeed 2377, which is the default for Swarm management. Additionally, check if there are any firewall rules or security groups on the manager node that could be blocking traffic from the new node. If you’ve verified these settings, the next step is to look into the Docker daemon logs on the manager for any clues about failed connection attempts.

      Additionally, you can run `docker info` on both the manager and the new node to see if there are any discrepancies in their configurations that might be affecting the join operation. Since you mentioned that both Docker services are running, it would be beneficial to check their versions for compatibility issues, as sometimes newer versions may introduce breaking changes. Also, ensure that the Docker service is properly configured to accept incoming connections on the appropriate ports (2377 for swarm management, 7946 for container communication, and 4789 for overlay networking). If all else fails, try restarting the Docker service on both nodes to rule out transient issues. Keep an eye on both the manager and new node logs during the join attempt for any specific error messages that can help trace the problem.


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