How can I find a Docker image with a specific tag in Docker registry on the Docker command line?

Question

I try to locate one specific tag for a Docker image. How can I do it on the command line? I want to avoid downloading all the images and then removing the unneeded ones.

Answer 1

When using CoreOS, jq is available to parse JSON data.

So like you were doing before, looking at library/centos:

$ curl -s -S 'https://registry.hub.docker.com/v2/repositories/library/centos/tags/' | jq '."results"[]["name"]' |sort
"6"
"6.7"
"centos5"
"centos5.11"
"centos6"
"centos6.6"
"centos6.7"
"centos7.0.1406"
"centos7.1.1503"
"latest"

The cleaner v2 API is available now, and that's what I'm using in the example. I will build a simple script docker_remote_tags:

#!/usr/bin/bash
curl -s -S "https://registry.hub.docker.com/v2/repositories/library/$@/tags/" | jq '."results"[]["name"]' |sort

Enables:

$ ./docker_remote_tags library/centos
"6"
"6.7"
"centos5"
"centos5.11"
"centos6"
"centos6.6"
"centos6.7"
"centos7.0.1406"
"centos7.1.1503"
"latest"

Reference:

jq: https://stedolan.github.io/jq/ | apt-get install jq

Answer 2

You can use Visual Studio Code to provide autocomplete for available Docker images and tags. However, this requires that you type the first letter of a tag in order to see autocomplete suggestions.

For example, when writing FROM ubuntu it offers autocomplete suggestions like ubuntu, ubuntu-debootstrap and ubuntu-upstart. When writing FROM ubuntu:a it offers autocomplete suggestions, like ubuntu:artful and ubuntu:artful-20170511.1

Answer 3

This script (docker-show-repo-tags.sh) should work for any Docker enabled host that has curl, sed, grep, and sort. This was updated to reflect the fact the repository tag URLs changed.

#!/bin/sh
#
# Simple script that will display Docker repository tags
# using basic tools: curl, sed, grep, and sort.
#
# Usage:
#   $ docker-show-repo-tags.sh ubuntu centos
for Repo in $* ; do
    curl -sS "https://hub.docker.com/r/library/$Repo/tags/" | \
        sed -e $'s/"tags":/\\\n"tags":/g' -e $'s/\]/\\\n\]/g' | \
        grep '^"tags"' | \
        grep '"library"' | \
        sed -e $'s/,/,\\\n/g' -e 's/,//g' -e 's/"//g' | \
        grep -v 'library:' | \
        sort -fu | \
        sed -e "s/^/${Repo}:/"
done

This older version no longer works.

#!/bin/sh
# WARNING: This no long works!
# Simple script that will display Docker repository tags.
#
# Usage:
#   $ docker-show-repo-tags.sh ubuntu centos
for Repo in $* ; do
  curl -s -S "https://registry.hub.docker.com/v2/repositories/library/$Repo/tags/" | \
    sed -e $'s/,/,\\\n/g' -e $'s/\[/\\\[\n/g' | \
    grep '"name"' | \
    awk -F\" '{print $4;}' | \
    sort -fu | \
    sed -e "s/^/${Repo}:/"
done

This is the output for a simple example:

$ docker-show-repo-tags.sh centos | cat -n
     1    centos:5
     2    centos:5.11
     3    centos:6
     4    centos:6.10
     5    centos:6.6
     6    centos:6.7
     7    centos:6.8
     8    centos:6.9
     9    centos:7.0.1406
    10    centos:7.1.1503
    11    centos:7.2.1511
    12    centos:7.3.1611
    13    centos:7.4.1708
    14    centos:7.5.1804
    15    centos:centos5
    16    centos:centos5.11
    17    centos:centos6
    18    centos:centos6.10
    19    centos:centos6.6
    20    centos:centos6.7
    21    centos:centos6.8
    22    centos:centos6.9
    23    centos:centos7
    24    centos:centos7.0.1406
    25    centos:centos7.1.1503
    26    centos:centos7.2.1511
    27    centos:centos7.3.1611
    28    centos:centos7.4.1708
    29    centos:centos7.5.1804
    30    centos:latest

Answer 4

I wrote a command line tool to simplify searching Docker Hub repository tags, available in my PyTools GitHub repository. It's simple to use with various command line switches, but most basically:

./dockerhub_show_tags.py repo1 repo2

It's even available as a Docker image and can take multiple repositories:

docker run harisekhon/pytools dockerhub_show_tags.py centos ubuntu

DockerHub

repo: centos
tags: 5.11
      6.6
      6.7
      7.0.1406
      7.1.1503
      centos5.11
      centos6.6
      centos6.7
      centos7.0.1406
      centos7.1.1503

repo: ubuntu
tags: latest
      14.04
      15.10
      16.04
      trusty
      trusty-20160503.1
      wily
      wily-20160503
      xenial
      xenial-20160503

If you want to embed it in scripts, use -q / --quiet to get just the tags, like normal Docker commands:

./dockerhub_show_tags.py centos -q
5.11
6.6
6.7
7.0.1406
7.1.1503
centos5.11
centos6.6
centos6.7
centos7.0.1406
centos7.1.1503