How do I self-host Vaultwarden on a VPS?

# After adding Docker's apt repository (docs.docker.com/engine/install/debian/)
sudo apt install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo docker run hello-world

mkdir -p ~/vaultwarden && cd ~/vaultwarden
# write docker-compose.yml and Caddyfile (below), then:
sudo docker compose up -d

services:
  vaultwarden:
    image: vaultwarden/server:latest
    container_name: vaultwarden
    restart: always
    environment:
      DOMAIN: "https://vault.example.com"
      SIGNUPS_ALLOWED: "true"
    volumes:
      - ./vw-data:/data

  caddy:
    image: caddy:2
    container_name: caddy
    restart: always
    ports:
      - 80:80
      - 443:443
      - 443:443/udp
    volumes:
      - ./Caddyfile:/etc/caddy/Caddyfile:ro
      - ./caddy-config:/config
      - ./caddy-data:/data
    environment:
      DOMAIN: "https://vault.example.com"
      EMAIL: "[email protected]"

{$DOMAIN} {
  tls {$EMAIL}
  encode zstd gzip
  reverse_proxy vaultwarden:80 {
    header_up X-Real-IP {remote_host}
  }
}

# Optional admin page: hash a long random password, put the result in ADMIN_TOKEN
sudo docker exec -it vaultwarden /vaultwarden hash

# Database backup while the server runs (SQLite online backup)
sqlite3 vw-data/db.sqlite3 ".backup '/root/backups/db-$(date +%Y%m%d-%H%M).sqlite3'"

# Also copy: vw-data/attachments/, vw-data/config.json, vw-data/rsa_key*