How to check if a Docker image with a specific tag exist locally? - bash

Question

I'd like to find out if a Docker image with a specific tag exists locally. I'm fine by using a bash script if the Docker client cannot do this natively.
Just to provide some hints for a potential bash script the result of running the docker images command returns the following:
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
rabbitmq latest e8e654c05c91 5 weeks ago 143.5 MB
busybox latest 8c2e06607696 6 weeks ago 2.433 MB
rabbitmq 3.4.4 a4fbaad9f996 11 weeks ago 131.5 MB

Answer 1

I usually test the result of docker images -q (as in this script):
if [[ "$(docker images -q myimage:mytag 2> /dev/null)" == "" ]]; then
# do something
fi
But since docker images only takes REPOSITORY as parameter, you would need to grep on tag, without using -q.
docker images takes tags now (docker 1.8+) [REPOSITORY[:TAG]]
The other approach mentioned below is to use docker inspect.
But with docker 17+, the syntax for images is: docker image inspect (on an non-existent image, the exit status will be non-0)
As noted by iTayb in the comments:
The docker images -q method can get really slow on a machine with lots of images. It takes 44s to run on a 6,500 images machine.
The docker image inspect returns immediately.
As noted in the comments by Henry Blyth:
If you use docker image inspect my_image:my_tag, and you want to ignore the output, you can add --format="ignore me" and it will print that literally.
You can also redirect stdout by adding >/dev/null but, if you can't do that in your script, then the format option works cleanly.

Answer 2

Try docker inspect, for example:
$ docker inspect --type=image treeder/hello.rb:nada
Error: No such image: treeder/hello.rb:nada
[]
But now with an image that exists, you'll get a bunch of information, eg:
$ docker inspect --type=image treeder/hello.rb:latest
[
{
"Id": "85c5116a2835521de2c52f10ab5dda0ff002a4a12aa476c141aace9bc67f43ad",
"Parent": "ecf63f5eb5e89e5974875da3998d72abc0d3d0e4ae2354887fffba037b356ad5",
"Comment": "",
"Created": "2015-09-23T22:06:38.86684783Z",
...
}
]
And it's in a nice json format.

Answer 3

tldr:
docker image inspect myimage:mytag
By way of demonstration...
success, found image:
$ docker image pull busybox:latest
latest: Pulling from library/busybox
Digest: sha256:32f093055929dbc23dec4d03e09dfe971f5973a9ca5cf059cbfb644c206aa83f
Status: Image is up to date for busybox:latest
$ docker image inspect busybox:latest >/dev/null 2>&1 && echo yes || echo no
yes
failure, missing image:
$ docker image rm busybox:latest
Untagged: busybox:latest
Untagged: busybox#sha256:32f093055929dbc23dec4d03e09dfe971f5973a9ca5cf059cbfb644c206aa83f
$ docker image inspect busybox:latest >/dev/null 2>&1 && echo yes || echo no
no
Reference:
https://docs.docker.com/engine/reference/commandline/image_inspect/

Answer 4

You can use like the following:
[ -n "$(docker images -q someimage:sometag)" ] || echo "does not exist"
Or:
[ -z "$(docker images -q someimage:sometag)" ] || echo "already exists"

Answer 5

With the help of Vonc's answer above I created the following bash script named check.sh:
#!/bin/bash
image_and_tag="$1"
image_and_tag_array=(${image_and_tag//:/ })
if [[ "$(docker images ${image_and_tag_array[0]} | grep ${image_and_tag_array[1]} 2> /dev/null)" != "" ]]; then
echo "exists"
else
echo "doesn't exist"
fi
Using it for an existing image and tag will print exists, for example:
./check.sh rabbitmq:3.4.4
Using it for a non-existing image and tag will print doesn't exist, for example:
./check.sh rabbitmq:3.4.3

Answer 6

In case you are trying to search for a docker image from a docker registry, I guess the easiest way to check if a docker image is present is by using the Docker V2 REST API Tags list service
Example:-
curl $CURLOPTS -H "Authorization: Bearer $token" "https://hub.docker.com:4443/v2/your-repo-name/tags/list"
if the above result returns 200Ok with a list of image tags, then we know that image exists
{"name":"your-repo-name","tags":["1.0.0.1533677221","1.0.0.1533740305","1.0.0.1535659921","1.0.0.1535665433","latest"]}
else if you see something like
{"errors":[{"code":"NAME_UNKNOWN","message":"repository name not known to registry","detail":{"name":"your-repo-name"}}]}
then you know for sure that image doesn't exist.

Answer 7

Using test
if test ! -z "$(docker images -q <name:tag>)"; then
echo "Exist"
fi
or in one line
test ! -z "$(docker images -q <name:tag>)" && echo exist

Answer 8

In bash script I do this to check if image exists by tag :
IMAGE_NAME="mysql:5.6"
if docker image ls -a "$IMAGE_NAME" | grep -Fq "$IMAGE_NAME" 1>/dev/null; then
echo "could found image $IMAGE_NAME..."
fi
Example script above checks if mysql image with 5.6 tag exists. If you want just check if any mysql image exists without specific version then just pass repository name without tag as this :
IMAGE_NAME="mysql"

Answer 9

Inspired by #rubicks's response above.
To check if the image exists already
image_name_tag="alpine:3.13.3"
docker image inspect ${image_name_tag} > /dev/null
echo $?
Pull if image does not exist
docker image inspect ${image_name_tag} > /dev/null || docker pull ${image_name_tag}
Demo execution
# image_name_tag="alpine:3.13.3"
#
# docker image inspect ${image_name_tag} > /dev/null
echo $?
Error: No such image: alpine:3.13.3
# echo $?
1
# docker image inspect ${image_name_tag} > /dev/null || docker pull ${image_name_tag}
Error: No such image: alpine:3.13.3
3.13.3: Pulling from library/alpine
9aae54b2144e: Pull complete
Digest: sha256:826f70e0ac33e99a72cf20fb0571245a8fee52d68cb26d8bc58e53bfa65dcdfa
Status: Downloaded newer image for alpine:3.13.3
docker.io/library/alpine:3.13.3
# docker image inspect ${image_name_tag} > /dev/null || docker pull ${image_name_tag}
$

Answer 10

Just a bit from me to very good readers:
Build
#!/bin/bash -e
docker build -t smpp-gateway smpp
(if [ $(docker ps -a | grep smpp-gateway | cut -d " " -f1) ]; then \
echo $(docker rm -f smpp-gateway); \
else \
echo OK; \
fi;);
docker run --restart always -d --network="host" --name smpp-gateway smpp-gateway:latest
Watch
docker logs --tail 50 --follow --timestamps smpp-gateway
Run
sudo docker exec -it \
$(sudo docker ps | grep "smpp-gateway:latest" | cut -d " " -f1) \
/bin/bash

Answer 11

for specific tag name
$ docker images --filter reference='<REPOSITORY>:TAG'
for "like clause" tagname:my_image_tag --> start my_ima*
$ docker images --filter reference='<REPOSITORY>:my_ima*'
if you want to someting "the image" for example delete all images tag started "my_ima" try this
docker rmi -f $(docker images -q --filter reference='myreponame:my_ima*')

Answer 12

I think this functionality should be implemented inside the docker build command (using a flag?), so that it avoids a lot of code duplication.
I used the same condition as the accepted answer inside a wrapper function called docker_build so that it does the necessary checks before calling the original docker build command.
# Usage: docker_build <...> (instead of docker build)
docker_build()
{
local arguments=("$#")
local index
for (( index=0; index<$#; index++ )); do
case ${arguments[index]} in
--tag)
local tag=${arguments[index+1]}
if [[ ! -z $(docker images -q "${tag}" 2> /dev/null) ]]; then
echo "Image ${tag} already exists."
return
fi
;;
esac
done
command docker build "$#"
}
Disclaimer: This is not ready for production because it works only with space-separated arguments in long format i.e --tag hello-world:latest. Also, this just modifies the docker build command only, all other commands remain same. If anyone has improvements, please let me know.
I felt like sharing this snippet because the idea of wrapping-standard-commands-in-bash-functions, to avoid code repetition, seemed more elegant and scalable than writing wrapper statements.

Answer 13

I like this because it is concise and has the proper semantics. If the image exists it is true what could be easier?
if [ $(docker image ls ${build_env} --format="true") ] ;
then
echo "does exist"
fi