How to fix Error response from daemon: 503 Service Unavailable in Docker

curl -I https://registry-1.docker.io/v2/

# Test DNS resolution
nslookup registry-1.docker.io

# Test TCP connectivity
nc -zv registry-1.docker.io 443

# Alternative connectivity test
</dev/tcp/registry-1.docker.io/443 && echo "Connected" || echo "Failed"

# On Linux with systemd
sudo systemctl daemon-reload
sudo systemctl restart docker
sudo systemctl status docker

# On macOS/Windows
# Restart Docker Desktop from the system tray/menu bar

{
  "proxies": {
    "http-proxy": "http://proxy.example.com:8080",
    "https-proxy": "http://proxy.example.com:8080",
    "no-proxy": "localhost,127.0.0.1"
  }
}

# Create systemd override directory
sudo mkdir -p /etc/systemd/system/docker.service.d

# Create proxy config file
sudo cat > /etc/systemd/system/docker.service.d/http-proxy.conf << EOF
[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"
EOF

# Reload and restart
sudo systemctl daemon-reload
sudo systemctl restart docker

# Check if the registry port is open
nc -zv your-registry.example.com 5000

# Test the registry API
curl http://your-registry.example.com:5000/v2/_catalog

# For HTTPS registries
curl https://your-registry.example.com/v2/_catalog

{
  "insecure-registries": ["your-registry.example.com:5000", "192.168.1.100:5000"]
}

sudo systemctl restart docker

#!/bin/bash
MAX_RETRIES=5
RETRY_DELAY=10

for i in \$(seq 1 \$MAX_RETRIES); do
  echo "Attempt \$i of \$MAX_RETRIES"
  if docker pull nginx:latest; then
    echo "Pull successful"
    exit 0
  fi
  echo "Failed, waiting \${RETRY_DELAY}s before retry..."
  sleep \$RETRY_DELAY
  RETRY_DELAY=\$((RETRY_DELAY * 2))
done

echo "All retries exhausted"
exit 1

{
  "registry-mirrors": ["https://mirror.gcr.io", "https://docker-mirror.example.com"]
}