24 Dec 2014
Basics Operation on a private docker registry

Getting started with a private Docker registry means a lot of searching on Google. Unfortunately, I couldn’t find a single site that would cover the basic operations such as search for images or tags. So here is a little write up, that I covers some of it.

In order to do push and pull operations on the private registry a user has to be authenticated (via nginx proxy) and logged in.
docker login docker.example.com
This will generate a .dockercfg file on the system where the login will be stored.

Search a private index

There are two methods for search available:

Docker Search

Docker search allows for some simple searches in the private index. For example:
docker search docker.example.com/ubuntu
However, if a nginx proxy sits in front of private Registry for authentication, you need to add user and password in front of the URL (Note: Unfortunately docker search will not take the login credentials as stored in the .dockercfg file):
``` docker search user:password@docker.example.com/ubuntu

NAME DESCRIPTION STARS OFFICIAL AUTOMATED library/ubuntu 0 ```
This will give you some information about the ubuntu repositories stored in the private registry, if one exists. docker search also allows for partial searches, so such as using ubu instead of ubuntu as search terms.

Docker Registry API

A less elegant but much more flexible way to search the registry is the use of the Docker Registry API.
curl -X GET https://user:passwd@docker.example.com/v1/search?q=ubuntu
or a more generic search:
curl -s -X GET https://user:passwd@ocker.example.com/v1/search
generates json lists, which can be further formated with a tool like jq For example the following command line:
curl -s -X GET https://user:passwd@docker.example.com/v1/search | jq '.results[].name'
would produce an output like this:
"library/nginx" "library/aws_cli" "library/redis" "library/debian" "library/busybox" "library/ubuntu" "library/commit_test" "library/logstash" "library/logstash-forwarder" "library/base"

Delete Operations

Delete operations are only available via the Docker Registry API. Note there is easy way to remove a image from a private registry, something that could help to reduce storage space. The reason for is that layers of one image may rely layers from other images.

Delete a repository tag

curl -X DELETE https://user:passwd@docker.example.com/v1/repositories/library/ubuntu/12.04

Delete a complete repository

(using the ubuntu repo as example) curl -X DELETE https://user:passwd@docker.example.com/v1/repositories/library/ubuntu/ ### Checking repository tags Here is an example (using the ubuntu repo) of checking the exixting tags in a repository:
curl -X GET https://user:passwd@docker.example.com/v1/repositories/library/ubuntu/tags
Example output:
{"12.04": "58c0a77963eaca09a68febbda32683812f3ff3615cc1ffa305cee67aa591fe26", "14.04": "86ce37374f40e95cfe8af7327c34ea9919ef216ea965377565fcfad3c378a2c3"}

Pushing Container images to the private Registry

Tagging a Container Image

In order to push a container image to a private Docker Registry the image needs to tagged accordingly. This can be done when the container is built.
docker build --rm -t docker.example.com/logstash-fwd .
This will automatically tag the images with the latest tag. To mark the images with a more specific version tag run the following command:
docker tag docker.example.com/logstash-fwd docker.example.com/logstash-fwd:0.0.1
After these two operations the image will have two tags 0.0.1 and latest. The latest tag is implicit if you pull the image with the registry name only.

Pushing the Container Image to the Registry

After the image is tagged correctly it can be pushed to the registry with command:
docker push docker.example.com/logstash-fwd:0.0.1 .
Note: For this operation you have to be logged in into the registry. The docker-client will not throw an error if you are not.

Til next time,
E.E at 23:51

24 Dec 2014 Basics Operation on a private docker registry

Docker Login