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Docker Tip #52: Referencing Containers and Images by Their Short IDs

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Container and image IDs are 64 character SHA-256 IDs. Most Docker commands truncate them to 12 characters, but you only need 4 chars.

When you’re hacking away on the terminal, sometimes it’s more convenient and even faster to reference a Docker container or image by its SHA-256 ID rather than name.

Let’s use the postgres:10.3-alpine image as a working example:
REPOSITORY          TAG                  IMAGE ID
postgres            10.3-alpine          f4f4231d6f0b
If you wanted to inspect this image, you have 3 options:
  • docker image inspect postgres:10.3-alpine
  • docker image inspect f4f4231d6f0b

Chances are you can copy / paste the image ID faster than you can manually type postgres:10.3-alpine. I did it 5 times and I can copy / paste the ID easily 50% faster.

But it gets better. Here’s a third and even faster way:

  • docker image inspect f4f4

You only need to reference the first 4 characters of the ID for it to work. Technically you could use the first 3 characters, but you may run into ID collisions.

This method works for both container and image IDs.

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