I want to know when I pulled a certain image, when you run docker images The Created field appear but the date that the image was pulled don't.
If you installed docker-engine from official repositories on your linux, it should be installed in /var/lib/docker, for your own configuration, find the respective path.
There is /var/lib/docker/image/aufs/repositories.json file where docker stores images with their sha256 values.
cat /var/lib/docker/image/aufs/repositories.json
Find the image you are looking after and copy it's sha256 hash somewhere.
Then:
ls /var/lib/docker/image/aufs/imagedb/content/sha256 -lash
Find the sha265 value you found in repositories.json then look at the date.
Related
If you ever attentively browse for docker images on https://hub.docker.com you may have once dissect all the commands composing an image of interest within a certain tag.
Great, but then you may have seen this kind of "translated" command when you click on a specific line of a command:
I may be wrong here because I'm not a Docker expert, but this seems to be an SHA-256 digest which refers to... something else inside the Hub.
My question is; how to find what exactly does it refer to, knowing the SHA value (3a7bff4e139bcacc5831fd70a035c130a91b5da001dd91c08b2acd635c7064e8)?
The SHA value you see is the digest of the file that was added.
For example, suppose you have the following dockerfile:
FROM scratch
ADD foo.txt /foo.txt
If you were to push that to dockerhub, you would see something like:
ADD file:b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c in /
where b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c is the digest of foo.txt.
There's no definitive way to reverse this information to obtain the file, considering ADD can do things like unpack tar archives.
With modern versions of Docker/buildkit, you might see the filename instead.
This is the same thing you see when using docker image history.
I would like to edit a docker images metadata for the following reasons:
I don't like an image parents EXPOSE, VOLUME etc declaration (see #3465, Docker-Team did not want to provide a solution), so I'd like to "un-volume" or "un-expose" the image.
I dont't like an image ContainerConfig (see docker inspect [image]) cause it was generated from a running container using docker commit [container]
Fix error durring docker build or docker run like:
cannot mount volume over existing file, file exists [path]
Is there any way I can do that?
Its a bit hacky, but works:
Save the image to a tar.gz file:
$ docker save [image] > [targetfile.tar.gz]
Extract the tar file to get access to the raw image data:
tar -xvzf [targetfile.tar.gz]
Lookup the image metadata file in the manifest.json file: There should be a key like .Config which contains a [HEX] number. There should be an exact [HEX].json in the root of the extracted folder.
This is the file containing the image metadata. Edit as you like.
Pack the extracted files back into an new.tar.gz-archive
Use cat [new.tar.gz] | docker load to re-import the modified image
Use docker inspect [image] to verify your metadata changes have been applied
EDIT:
This has been wrapped into a handy script: https://github.com/gdraheim/docker-copyedit
I had come across the same workaround - since I have to edit the metadata of some images quite often (fixing an automated image rebuild from a third party), I have create a little script to help with the steps of save/unpack/edit/load.
Have a look at docker-copyedit. It can remove or overrides volumes as well as set other metadata values like entrypoint and cmd.
When I download a Docker image, it downloads dependencies, but only displays their hashes. Why does it not display what it is downloading?
For example:
➜ ~ docker run ubuntu:16.04
Unable to find image 'ubuntu:16.04' locally
16.04: Pulling from library/ubuntu
b3e1c725a85f: Downloading 40.63 MB/50.22 MB
4daad8bdde31: Download complete
63fe8c0068a8: Download complete
4a70713c436f: Download complete
bd842a2105a8: Download complete
What's the point in only telling me that it's downloading b3e1c725a85f, etc.?
An image is created on layers of filesystems represented by hashes. After it's creation, the base image tag may point to a completely different set of hashes without affecting any images built off of it. And these layers are based on things like run commands, the tag to call it something like ubuntu:16.04 is only added after the image is made.
So the best that could be done is to say 4a70713c436f is based on adding some directory based on a hash of an input folder itself, or a multi-line run command, neither of which makes for a decent UI. The result may have no tagged name, or it could have multiple tagged names. So the simplest solution is to output what's universal and unchanging for all scenarios, an unchanging hash.
To rephrase that pictorially:
b3e1c725a85f: could be ubuntu:16.04, ubuntu:16, ubuntu:latest, some.other.registry:5000/ubuntu-mirror:16.04
4daad8bdde31: could be completely untagged, just a run command
63fe8c0068a8: could be completely untagged, just a copy file
4a70713c436f: could point to a tagged base image where that tag has since changed
bd842a2105a8: could be created with a docker commit command (eek)
I'd like to pull the images of CentOS, Tomcat, ... using their sha256 code, like in
docker pull myimage#sha256:0ecb2ad60
But I can't find the sha256-code to use anywhere.
I checked the DockerHub repository for any hint of the sha256-code, but couldn't find any. I downloaded the images by their tag
docker pull tomcat:7-jre8
and checked the image with docker inspect to see if there's a sha256 code in the metadata, but there is none (adding the sha256 code of the image would probably change the sha256 code).
Do I have to compute the sha256 code of an image myself and use that?
Latest answer
Edit suggested by OhJeez in the comments.
docker inspect --format='{{index .RepoDigests 0}}' $IMAGE
Original answer
I believe you can also get this using
docker inspect --format='{{.RepoDigests}}' $IMAGE
Works only in Docker 1.9 and if the image was originally pulled by the digest. Details are on the docker issue tracker.
You can get it by docker images --digests
REPOSITORY TAG DIGEST IMAGE ID CREATED SIZE
docker/ucp-agent 2.1.0 sha256:a428de44a9059f31a59237a5881c2d2cffa93757d99026156e4ea544577ab7f3 583407a61900 3 weeks ago 22.3 MB
Simplest and most concise way is:
docker images --no-trunc --quiet $IMAGE
This returns only the sha256:... string and nothing else.
e.g.:
$ docker images --no-trunc --quiet debian:stretch-slim
sha256:220611111e8c9bbe242e9dc1367c0fa89eef83f26203ee3f7c3764046e02b248
Edit:
NOTE: this only works for images that are local. You can docker pull $IMAGE first, if required.
Just saw it:
When I pull an image, the sha256 code is diplayed at the bottom of the output (Digest: sha....):
docker pull tomcat:7-jre8
7-jre8: Pulling from library/tomcat
902b87aaaec9: Already exists
9a61b6b1315e: Already exists
...
4dcef5c50d60: Already exists
Digest: sha256:c34ce3c1fcc0c7431e1392cc3abd0dfe2192ffea1898d5250f199d3ac8d8720f
Status: Image is up to date for tomcat:7-jre8
This sha code
sha256:c34ce3c1fcc0c7431e1392cc3abd0dfe2192ffea1898d5250f199d3ac8d8720f
can be used to pull the image afterwards with
docker pull tomcat#sha256:c34ce3c1fcc0c7431e1392cc3abd0dfe2192ffea1898d5250f199d3ac8d8720f
This way you can be sure that the image is not changed and can be safely used for production.
I found the above methods to not work in some cases. They either:
don't deal well with multiple images with the same hash (in the case of .RepoDigests suggestion - when you want to use a specific registry path)
don't work well when pushing the image to registries
(in the case of .Id where it's a local hash, not the hash in the
registry).
The below method is delicate, but works for extracting the specific full 'name' and hash for a specific pushed container.
Here's the scenario - An image is uploaded separately to 2 different projects in the same repo, so querying RepoDigests returns 2 results.
$ docker inspect --format='{{.RepoDigests}}' gcr.io/alpha/homeapp:latest
[gcr.io/alpha/homeapp#sha256:ce7395d681afeb6afd68e73a8044e4a965ede52cd0799de7f97198cca6ece7ed gcr.io/beta/homeapp#sha256:ce7395d681afeb6afd68e73a8044e4a965ede52cd0799de7f97198cca6ece7ed]
I want to use the alpha result, but I can't predict which index it will be. So I need to manipulate the text output to remove the brackets and get each entry on a separate line. From there I can easily grep the result.
$ docker inspect --format='{{.RepoDigests}}' gcr.io/alpha/homeapp:latest | sed 's:^.\(.*\).$:\1:' | tr " " "\n" | grep alpha
gcr.io/alpha/homeapp#sha256:ce7395d681afeb6afd68e73a8044e4a965ede52cd0799de7f97198cca6ece7ed
In addition to the existing answers, you can use the --digests option while doing docker images to get a list of digests for all the images you have.
docker images --digests
You can add a grep to drill down further
docker images --digests | grep tomcat
You can find it at the time of pulling the image from the respective repository. Below command mentions Digest: sha256 at the time of pulling the docker image.
09:33 AM##~::>docker --version
Docker version 19.03.4, build 9013bf5
Digest: sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d
09:28 AM##~::>docker pull ubuntu
Using default tag: latest
latest: Pulling from library/ubuntu
7ddbc47eeb70: Pull complete
c1bbdc448b72: Pull complete
8c3b70e39044: Pull complete
45d437916d57: Pull complete
**Digest: sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d**
Status: Downloaded newer image for ubuntu:latest
docker.io/library/ubuntu:latest
Once, the image is downloaded, we can do the following
"ubuntu#sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d"
09:36 AM##~::>docker inspect ubuntu | grep -i sha256
"Id": "sha256:775349758637aff77bf85e2ff0597e86e3e859183ef0baba8b3e8fc8d3cba51c",
**"ubuntu#sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d"**
"Image": "sha256:f0caea6f785de71fe8c8b1b276a7094151df6058aa3f22d2902fe6b51f1a7a8f",
"Image": "sha256:f0caea6f785de71fe8c8b1b276a7094151df6058aa3f22d2902fe6b51f1a7a8f",
"sha256:cc967c529ced563b7746b663d98248bc571afdb3c012019d7f54d6c092793b8b",
"sha256:2c6ac8e5063e35e91ab79dfb7330c6154b82f3a7e4724fb1b4475c0a95dfdd33",
"sha256:6c01b5a53aac53c66f02ea711295c7586061cbe083b110d54dafbeb6cf7636bf",
"sha256:e0b3afb09dc386786d49d6443bdfb20bc74d77dcf68e152db7e5bb36b1cca638"
This should have been the Id field, that you could see in the old deprecated Docker Hub API
GET /v1/repositories/foo/bar/images HTTP/1.1
Host: index.docker.io
Accept: application/json
Parameters:
namespace – the namespace for the repo
repo_name – the name for the repo
Example Response:
HTTP/1.1 200
Vary: Accept
Content-Type: application/json
[{"id": "9e89cc6f0bc3c38722009fe6857087b486531f9a779a0c17e3ed29dae8f12c4f",
"checksum": "b486531f9a779a0c17e3ed29dae8f12c4f9e89cc6f0bc3c38722009fe6857087"},
{"id": "ertwetewtwe38722009fe6857087b486531f9a779a0c1dfddgfgsdgdsgds",
"checksum": "34t23f23fc17e3ed29dae8f12c4f9e89cc6f0bsdfgfsdgdsgdsgerwgew"}]
BUT: this is not how it is working now with the new docker distribution.
See issue 628: "Get image ID with tag name"
The /v1/ registry response /repositories/<repo>/tags used to list the image ID along with the tag handle.
/v2/ only seems to give the handle.
It would be useful to get the ID to compare to the ID found locally. The only place I can find the ID is in the v1Compat section of the manifest (which is overkill for the info I want)
The current (mid 2015) answer is:
This property of the V1 API was very computationally expensive for the way images are stored on the backend. Only the tag names are enumerated to avoid a secondary lookup.
In addition, the V2 API does not deal in Image IDs. Rather, it uses digests to identify layers, which can be calculated as property of the layer and are independently verifiable.
As mentioned by #zelphir, using digests is not a good way since it doesn't exist for a local-only image. I assume the image ID sha is the most accurate and consistent across tags/pull/push etc.
docker inspect --format='{{index .Id}}' $IMAGE
Does the trick.
Just issue docker pull tomcat:7-jre8 again and you will get what you want.
I am playing around with Docker for a couple of days and I already made some images (which was really fun!). Now I want to persist my work and came to the save and export commands, but I don't fully understand them.
What is the difference between save and export in Docker?
The short answer is:
save will fetch an image : for a VM or a physical server, that would be the installation .ISO image or disk. The base operating system.
It will pack the layers and metadata of all the chain required to build the image. You can then load this "saved" images chain into another docker instance and create containers from these images.
export will fetch the whole container : like a snapshot of a regular VM. Saves the OS of course, but also any change you made, any data file written during the container life. This one is more like a traditional backup.
It will give you a flat .tar archive containing the filesystem of your container.
Edit: as my explanation may still lead to confusion, I think that it is important to understand that one of these commands works with containers, while the other works with images.
An image has to be considered as 'dead' or immutable, starting 0 or 1000 containers from it won't alter a single byte. That's why I made a comparison with a system install ISO earlier. It's maybe even closer to a live-CD.
A container "boots" the image and adds an additional layer on top of it. This layer stores any change on the container (created/changed/removed files...).
There are two main differences between save and export commands.
save command saves whole image with history and metadata but export command exports only files structure (without history and metadata). So the exported tar file will be smaller then the saved one.
When you use exported file system for creating a new image then this new image will not contain any USER, EXPOSE, RUN etc. commands from your Dockerfile. Only file structure will be transferred.
So when you are using mentioned keywords in your Dockerfile then you cannot use export command for transferring image to another machine - you need always use save command.
export: container (filesystem)->image tar.
import: exported image tar-> image. Only one layer.
save: image-> image tar.
load: saved image tar->image. All layers will be recovered.
From Docker in Action, Second Edition p190.
Layered images maintain the history of the image, container-creation metadata, and old files that might have been deleted or overridden.
Flattened images contain only the current set of files on the filesystem.
The exported image will not have any layer or history information saved, so it will be smaller and you will not be able to rollback.
The saved image will have layer and history information, so larger.
If giving this to a customer, the Q is do you want to keep those layers or not?
Technically, save/load works with repositories which can be one or more of images, also referred to as layers. An image is a single layer within a repo. Finally, a container is an instantiated image (running or not).
Docker save Produces a tar file repo which contains all parent layers, and all tags + versions, or specified repo:tag, for each argument provided from image.
Docker export Produces specified file(can be tar or tgz) with flat contents without contents of specified volumes from Container.
docker save need to use on docker image while docker export need to use on container(just like running image)
Save Usage
docker save [OPTIONS] IMAGE [IMAGE...]
Save an image(s) to a tar archive (streamed to STDOUT by default)
--help=false Print usage -o, --output="" Write to a file,
instead of STDOUT
export Usage
docker export [OPTIONS] CONTAINER
Export the contents of a container's filesystem as a tar archive
--help=false Print usage -o, --output="" Write to a file,
instead of STDOUT