Note_Tech

All technological notes.

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Docker - Storage

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• Docker - Storage
  • Storage Drivers
  • File System
  • Layer Architecture
  • Command Commands

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Storage Drivers

Manages the layer architecture. Common drivers:

• aufs
• zfs
• btrfs
• device mapper
• overlay
• overlay2

Dock choose bases on the OS

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File System

• /var/lib/docker: data root directory on the host
  • aufs： old storage driver
  • overlay2： current storage driver; Image layers
  • containers： runtime data
    • <container-id>/
      • config.v2.json: container config
      • hostconfig.json: runtime settings
      • *.log: container logs (stdout/stderr); docker logs
  • image： image metadata
  • volumes： persistent data
    • <volume-name>/_data/

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Layer Architecture

• uses a Union File System (like OverlayFS).
• How it works:
  • Container layer adds a read-write layer on top
  • Image layers = read-only
• copy-on-write machenism
  • Modify a file: copy-on-write
  • Original image stays unchanged

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Types of mounts

• Volume mounts:
  • mount on docker volume
• Bind mounts:
  • host-based storage: docker run -v /host/path:/container/path nginx

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Command Commands

Command	Description
docker volume ls	List volumes
docker volume create vol_name	Create a volume
docker volume update	Update a volume (cluster volumes only)
docker volume rm vol_name	Remove one or more volumes