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Common issues

The problems people run into most, and their fixes.

Being written

This page is being written. It will cover:

  • The dashboard cannot be reached
  • A certificate is not issued
  • A domain shows 404 or a bad gateway
  • An app made from a template does not start

A network cannot start: "Pool overlaps"​

Some apps never start, often the logging backend and its collector, and their tasks are rejected with:

invalid pool request: Pool overlaps with other one on this address space

Docker's own log, journalctl -u docker, repeats Failed creating ingress network with the same words.

A swarm takes its networks' addresses from 10.0.0.0/8, a /24 each: 10.0.0.0/24 for its ingress network, 10.0.1.0/24 for the next, and so on. Docker's own networks on the server, docker0 and docker_gwbridge, take theirs from default-address-pools in /etc/docker/daemon.json. When that setting is also in 10.0.0.0/8, both hand out the same subnets in the same order, and a swarm network given one that a network of Docker's own holds cannot be created on the server. Check:

docker info --format '{{range .DefaultAddressPools}}{{.Base}} {{end}}'
docker network inspect bridge docker_gwbridge -f '{{.Name}} {{range .IPAM.Config}}{{.Subnet}}{{end}}'

To fix it, give Docker's own networks another range, and have Docker make them again:

  1. In /etc/docker/daemon.json, change the setting to a range your server's own networks do not use, or remove it to have Docker's defaults:

    "default-address-pools": [{ "base": "172.16.0.0/12", "size": 20 }]

  2. Reset Docker's own networks, on the server:

    sudo systemctl stop docker docker.socket
    sudo mv /var/lib/docker/network/files/local-kv.db /root/local-kv.db.bak
    sudo ip link delete docker0
    sudo ip link delete docker_gwbridge
    sudo systemctl start docker

Every container on the server restarts. The swarm, its services and its networks are kept; networks made with docker network create on this server alone are forgotten. Docker makes docker0 and docker_gwbridge again from the new range, and the swarm's networks start.