Is there a setting I can change to have docker check for updated images, instead of using its cache forever?

General
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One of our images was updated four days ago, but docker would only use the month-old cached version until I ran docker system prune -a, which is rather drastic. There’s also a --no-cache options. Is there an option where docker uses its cache, but actually looks for more recent images (as a web browser does)?

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Plain Docker pulls a tag during a deployment when it’s not present in the local repo cache.
Docker Swarm on the other hand allways pulls the tag on every deployment.

On plan Docker, you can specificly update a mutable tag with docker pull image:tag
It is neither desirable to have mutable tags in production, nor to have them automaticly updated in the background.

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Thank you, but I can’t relate your answer to my question.

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Not including Docker Swarm (since I don’t use it and can’t speak to its capability), my understanding is that you need to execute a “docker pull” to download the latest version of the image (which you’ve done) and then when you redeploy (IE: “docker stop / docker rm / docker run”) it uses the most updated version of the image and only downloads updates if there is no local image.

On my system I’ve written a script in cron to do a docker pull and then if anything downloads, stop, rm and deploy the container again. I’ve not heard/read the term “mutable tags”, but if it’s like using “:latest” then I do that most of the time for my own sanity. If I read right, the idea that automatic updates on a production system is undesirable is more the stuff of opinions, and one I don’t necessarily always share.

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@dougnchannel You, are right, I shouldhave starte with: no, there is no such option buildin in Docker. That said, you might want to take a look at Watchtower. Periodicly it checks if an updated image exists for your containers. For each updateable image, it pulls the new image, deletes the old container and create a new container based on the new image having the same configuration as the old container

@cincitech
mutable as in changeble. Even though the tag is fixed, its does not point to a defined version of the metadata and all its image layers, thus not the same image.