Docker: The Portable App Container

The Instructor's Perspective

In our labs, we want to be able to move our applications around easily. If an LXC is a “backpack” for a service, then Docker is the standardized “shipping container.” It ensures that your application runs the same way, whether it’s on your laptop or a production server. It’s a key part of our Stack.

Why use it?

• Portability: Run the same container anywhere.
• Isolation: Each container has its own environment and dependencies.
• Ecosystem: Huge library of pre-built images on Docker Hub.
• Scalability: Easy to scale services using Docker Swarm or Compose.

Container Reliability (The PACE Plan)

Deployment Discipline

P (Primary): Dedicated Docker Swarm Cluster (running on multiple Proxmox nodes). A (Alternate): Standalone Docker Compose on a single LXC or VM. C (Contingency): Fresh deployment using an Ansible playbook and latest backups. E (Emergency): Run the application as a standard process on any available Linux host.

Standard Operating Procedure (SOP) Best Practices

1. Use Compose: Always use Docker Compose for managing multi-container applications.
2. Tag Your Images: Don’t just use latest. Use specific version tags for consistency.
3. External Storage: Store your persistent data on a NAS or ZFS pool.
4. Monitoring: Use Grafana or Portainer to keep an eye on your containers.

Docker Knowledge Tree

TABLE join(sort(rows.file.link), " | ") as Documents
FLATTEN regexreplace(file.folder, ".*/", "") as lastPart
WHERE contains(file.folder, this.file.folder) AND file.name != this.file.name
GROUP BY lastPart as Folder
SORT lastPart

Recent Activity

TABLE 
  file.ctime AS "Created", 
  file.mtime AS "Updated"
WHERE (file.cday >= date(today) - dur(7 days) OR file.mday >= date(today) - dur(7 days))
  AND contains(file.folder, this.file.folder) AND file.name != this.file.name
SORT file.mtime DESC
LIMIT 10

Check for Understanding

• What is the main difference between a Docker Swarm (Primary) and a Standalone Compose (Alternate)?
• Why is it important to tag your Docker images with specific versions?

Related: LXC, Proxmox, Apt Cacher NG