Check if Docker image exists in cloud repo

Question

Say I have this image tag "node:9.2" as in FROM node:9.2...

is there an API I can hit to see if image with tag "node:9.2" exists and can be retrieved, before I actually try docker build ...?

Does this answer your question? [Check if image:tag combination already exists on docker hub](https://stackoverflow.com/questions/32113330/check-if-imagetag-combination-already-exists-on-docker-hub) — mat007, Aug 17 '22 at 09:28

Adiii · Answer 1 · 2018-06-20T18:17:58.167

8

This script will build only if image not exist.

update for V2

function docker_tag_exists() {
    curl --silent -f -lSL https://hub.docker.com/v2/repositories/$1/tags/$2 > /dev/null 
}

Use above function for v2

#!/bin/bash
function docker_tag_exists() {
    curl --silent -f -lSL https://index.docker.io/v1/repositories/$1/tags/$2 > /dev/null 

}

if docker_tag_exists library/node 9.11.2-jessie; then
    echo "Docker image exist,...."
    echo "pulling existing docker..."
    #so docker image exist pull the docker image
    docker pull node:9.11.2-jessie
else 
    echo "Docker image not exist remotly...."
    echo "Building docker image..."
    #build docker image here with absoult or retlative path
    docker build -t nodejs .

fi

With little modification from the link below. If the registry is private u check this link With username and password

edited Jun 20 '18 at 18:17

answered Jun 20 '18 at 10:00

Adiii

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thanks! do you an example using v2 of the Docker registry? – Alexander Mills Jun 20 '18 at 18:09
cool thanks, this worked: `curl --silent -f -lSL https://hub.docker.com/v2/repositories/library/node/tags` – Alexander Mills Jun 20 '18 at 18:55
So I guess `https://hub.docker.com/v2` does not required auth, but `https://registry-1.docker.com/v2` does require auth? – Alexander Mills Jun 20 '18 at 18:55
1

auth only required if you are pulling from private repo not in this case – Adiii Jun 21 '18 at 05:23
Will this give a false negative if there's a network hiccup during the check? – mpartel Dec 11 '18 at 18:24

score 3 · Answer 2 · answered Apr 14 '20 at 09:42

3

If you have "experimental": enabled set for the Docker daemon then you can use this command:

docker manifest inspect node:9.2

answered Apr 14 '20 at 09:42

peetasan

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emory · Accepted Answer · 2018-06-20T01:52:09.673

-11

Yes.

docker image pull node:9.2

edited Jun 20 '18 at 01:52

answered Jun 20 '18 at 01:45

emory

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hmmm, I don't want to actual download the image, just check if it exists, does this do that? – Alexander Mills Jun 20 '18 at 01:48
@AlexanderMills if the image is available it will download the image – emory Jun 20 '18 at 01:53
yeah in this case I am just looking to ping the Docker hub server/registry to see if the image exists - this is so I can give the user a good warning if the image doesn't exist, in advance instead of making them wait too long – Alexander Mills Jun 20 '18 at 02:10
What if the image exists, but it is private and the user does not have access? I suspect from an API pov it is the same as if the image did not exist. – emory Jun 20 '18 at 03:03
Is there a command like this that doesn't require auth? In order to get this to work, I first had to run `docker login -u -p ` ... – Alexander Mills Jun 23 '18 at 03:06
@AlexanderMills I seriously doubt it. – emory Jun 26 '18 at 00:07
hmmm yeah, contrary evidence would be that I can install Docker images without authenticating. E.g., I can do `docker build` with an image that I don't have on my local machine yet, and still I don't have to auth. So there must be some pull command that doesn't require auth? – Alexander Mills Jun 26 '18 at 01:23
If private/img is an image you dont have locally and `docker image pull priv/img` fails bc lack of authentication but you can build a Dockerfile like `FROM priv/img ...` then i am not sure what is the point pf authentication. – emory Jun 26 '18 at 10:03
I also use this way because curl responds with 404. Image with tag is definitely exists. – kyb Feb 08 '22 at 13:28

Check if Docker image exists in cloud repo

3 Answers3