Question 336138 in Ubuntu Question posted in
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Ubuntu – Can't create Docker Swarm because of connection failure

  1. Target: Creating a Docker Swarm

  2. Condition:

    • Host A: Ubuntu 23.10
    • Host B: Mac Sonoma 14.1.2

  3. Operation:

    • In Host A: 
      docker swarm init
    • In Host B: 
      docker swarm join --token SWMTKN-1-3o2m78qf57hy2zikfx8p2yc7hrn63edlmlixwrq7bh28xws7zx-9oirn0wh3mbrdui3kcwytl560 192.168.65.9:2377

  4. Error:

    Error response from daemon: rpc error: code = Unavailable desc = connection error:
desc = "transport: Error while dialing dial tcp 192.168.65.9:2377: connect: no route to host"

  5. What I’ve done so far:

    • Installed firewalld on Ubuntu Host A, but for unknown reason it caused system crash. I guess this is because Ubuntu 23.10 doesn’t support firewalld anymore.
    • Use ufw command to open communication port on Ubuntu Host A, but it doesn’t work.

  6. Asking for help: I saw other people can easily run the "docker swarm join" command in the tutorial. Why I got this problem? Any one can help me out? Really appreciate your help.

Tags:

2

Answers


  1. 0

    You need to open several ports for the communication (On A as well ass B hosts):

    As Docker documentations says:

    • Port 2377 TCP for communication with and between manager nodes
    • Port 7946 TCP/UDP for overlay network node discovery
    • Port 4789 UDP (configurable) for overlay network traffic

    Furthermore:

    • Port 2376 TCP for secure Docker client communication.

    Set UFW config (Or disable the UFW as you mentioned in your question):

    ufw allow 22/tcp
ufw allow 2376/tcp
ufw allow 2377/tcp
ufw allow 7946/tcp
ufw allow 7946/udp
ufw allow 4789/udp
ufw reload
ufw enable
systemctl restart docker

    You can check the IpTables configuration as well based on this documentation: https://www.digitalocean.com/community/tutorials/how-to-configure-the-linux-firewall-for-docker-swarm-on-ubuntu-16-04

    BUT, The "Docker for Mac" uses different networking as Linux based and that can cause turbulence in Docker Swarm. Here is a ticket for it: https://github.com/moby/swarmkit/issues/1146#issuecomment-231412874

    Based on the above ticket the Mac can run only single-node Swarm right now. (I didn’t find fix for it)

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  2. 0
    1. Ensure that both are connected to a local network (connected inside a network)

    You need to connect machines together verify that by ping (if you are using a firewall then ping ICMP packets wont work). do a curl request from A to B

    1. Check firewall status ufw status if its status: inactive then its not a problem else disable the firewall(DISCLAIMER: may become a security issue) or Open only specific ports like 2376, 4789, 2377, 7946.
    ufw allow 7946/tcp
ufw allow 7946/udp
ufw allow 2376/tcp
ufw allow 4789/udp
ufw allow 2377/tcp

    sudo ufw reload

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