How to fix Error response from daemon: error while joining swarm: failed to join the cluster in Docker

# Test connectivity to the manager node on port 2377
telnet <manager-ip> 2377

# Or using netcat
nc -zv <manager-ip> 2377

# Or using curl (will show connection but protocol error, which is OK)
curl -v telnet://<manager-ip>:2377

# On the manager node, verify the advertised address
docker info | grep -A 5 "Swarm"

sudo firewall-cmd --permanent --add-port=2377/tcp
sudo firewall-cmd --permanent --add-port=7946/tcp
sudo firewall-cmd --permanent --add-port=7946/udp
sudo firewall-cmd --permanent --add-port=4789/udp
sudo firewall-cmd --reload

sudo ufw allow 2377/tcp
sudo ufw allow 7946/tcp
sudo ufw allow 7946/udp
sudo ufw allow 4789/udp
sudo ufw reload

sudo iptables -A INPUT -p tcp --dport 2377 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 7946 -j ACCEPT
sudo iptables -A INPUT -p udp --dport 7946 -j ACCEPT
sudo iptables -A INPUT -p udp --dport 4789 -j ACCEPT
sudo iptables-save | sudo tee /etc/iptables/rules.v4

# On manager
date

# On joining node
date

sudo apt-get install -y chrony
sudo systemctl enable chrony
sudo systemctl start chrony

sudo yum install -y chrony
sudo systemctl enable chronyd
sudo systemctl start chronyd

# Using chrony
sudo chronyc makestep

# Using ntpdate (if available)
sudo ntpdate pool.ntp.org

# Manual sync from manager (quick fix)
sudo date --set="$(ssh user@manager-node date)"

chronyc tracking
# or
timedatectl status

# Run on a manager node
docker swarm join-token worker

# Run on a manager node
docker swarm join-token manager

# Rotate the worker token
docker swarm join-token --rotate worker

# Rotate the manager token
docker swarm join-token --rotate manager

# Force leave any existing swarm
docker swarm leave --force

# Verify the node is no longer in swarm mode
docker info | grep Swarm
# Should show: Swarm: inactive

# Stop Docker
sudo systemctl stop docker

# Remove swarm state (this is safe on a node that isn't a manager)
sudo rm -rf /var/lib/docker/swarm

# Start Docker
sudo systemctl start docker

# Try joining again
docker swarm join --token <token> <manager-ip>:2377

hostname
cat /etc/hostname

# Set a unique hostname
sudo hostnamectl set-hostname swarm-node-01

# Update /etc/hosts
sudo bash -c 'echo "127.0.0.1 swarm-node-01" >> /etc/hosts'

# Restart Docker to pick up the change
sudo systemctl restart docker

docker info | grep Name

echo $HTTP_PROXY $HTTPS_PROXY $http_proxy $https_proxy
env | grep -i proxy

cat /etc/systemd/system/docker.service.d/http-proxy.conf

[Service]
Environment="HTTP_PROXY=http://proxy.example.com:8080"
Environment="HTTPS_PROXY=http://proxy.example.com:8080"
Environment="NO_PROXY=localhost,127.0.0.1,<manager-ip>,<other-node-ips>"

sudo systemctl daemon-reload
sudo systemctl restart docker

unset HTTP_PROXY HTTPS_PROXY http_proxy https_proxy
docker swarm join --token <token> <manager-ip>:2377

# Restart Docker
sudo systemctl restart docker

# Wait a moment for it to fully start
sleep 5

# Verify Docker is running
docker info

# Retry the join
docker swarm join --token <token> <manager-ip>:2377

# View recent Docker daemon logs
sudo journalctl -u docker --since "10 minutes ago"

# Follow logs while attempting join (in another terminal)
sudo journalctl -u docker -f

# Join with explicit advertise address
docker swarm join \
  --advertise-addr <this-node-ip> \
  --token <token> \
  <manager-ip>:2377

# Check current advertise address
docker info | grep "Advertise Address"

# If incorrect, you may need to reinitialize (WARNING: this affects the whole cluster)
# Only do this if absolutely necessary and you understand the implications
docker swarm init --force-new-cluster --advertise-addr <correct-ip>