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Docker Docker & Containers: From Zero to Production Docker Hub Docker Images Module 2 — Docker Images

Pulling Images from Docker Hub — Tags, Versions, Digests

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R Ram Pothuraju Reading…

What You'll Learn

Beginner

  • How to search for and pull images from Docker Hub
  • The difference between tags, versions, and digests
  • How to choose the right image (official vs community)

Searching for Images

Terminalbash
# Search from the command line
docker search nginx

# Or browse https://hub.docker.com in your browser

Pulling Images

Terminalbash
# Pull the latest tag (not recommended for production)
docker pull nginx

# Pull a specific version
docker pull nginx:1.25.3

# Pull an Alpine-based variant (smaller)
docker pull nginx:alpine

# Pull by digest (immutable — always gets the exact same image)
docker pull nginx@sha256:abc123...

Tags vs Digests

TagsDigests
Human-readable labelSHA256 hash of the image
Can change over timeImmutable — never changes
nginx:1.25nginx@sha256:abc123...
When to use digests
In production, use digests for guaranteed reproducibility. nginx:1.25 might point to a different image tomorrow. A digest always points to the exact same image.

Image Variants — slim, alpine, full

TagSizeWhen to use
python:3.11~900 MBFull Debian — maximum compatibility
python:3.11-slim~150 MBStripped Debian — smaller, good default
python:3.11-alpine~50 MBAlpine Linux — smallest, may have compatibility issues

Practical Exercise

Run docker search python
Run docker pull python:3.11-slim
Run docker images — see the size
Run docker image inspect python:3.11-slim

Key Takeaways

  • docker pull <image>:<tag> downloads an image from Docker Hub.
  • Tags are human-readable but mutable. Digests (SHA256) are immutable.
  • Use official images for security. Review community images before using.
  • Variants: full (compatible), slim (balanced), alpine (smallest).
  • In production, pin versions or use digests. Avoid latest.
Previously: Lesson 09 covered image layers.
Today: You learned: Pull images, understand tags vs digests, choose the right version.
Next: Lesson 11 shows how to build your own image.
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