Swarm Configs

• Map files/strings stored in Raft Log to any file path in tasks
• Ideal For nginx/mysql/etc. configs
• Now you don't need to custom image or bind-mount to host
• 17.06+ similar to Secrets but can go anywhere in container
  • Immutable, so rotation process is key
  • Removable once services are removed
  • Strings saved to Swarm Raft Log (instant HA)
• Private keys should still use Secrets (RAM disks, enc at rest)

Examples

• Create a new Config from a nginx config
  • docker config create nginx01 ./nginx.conf
• Creating a Service with a Config
  • docker service create --config source=nginx01,target=/etc/nginx/conf.d/default.conf
• Creating new Config to replace old
  • docker config create nginx01 ./nginx.conf
• Updating Service with new Config
  • docker service update --config-rm nginx01 --config-add source=nginx02,target=/etc/nginx/conf.d/default.conf

Swarm Configs in Stack Files

version: "3.3"   # minimum version
services:
  web:
    image: nginx
    configs:
      - source: nginx-proxy
        target: /etc/nginx/conf.d/default.conf
configs:
  nginx-proxy:
    file: ./nginx-app.conf

External links

• https://docs.docker.com/engine/swarm/configs/