Exploring Docker commands: docker image

image is a management command. To get a list of all its commands we can run

$ docker image

$ docker image --help

Usage: docker image COMMAND

Manage images

Commands:
build Build an image from a Dockerfile
history Show the history of an image
import Import the contents from a tarball to create a filesystem image
inspect Display detailed information on one or more images
load Load an image from a tar archive or STDIN
ls List images
prune Remove unused images
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
rm Remove one or more images
save Save one or more images to a tar archive (streamed to STDOUT by default)
tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

Run 'docker image COMMAND --help' for more information on a command.

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docker image history

% docker image history --help

Usage: docker image history [OPTIONS] IMAGE

Show the history of an image

Options:

--format string Pretty-print images using a Go template

-H, --human Print sizes and dates in human readable format (default true)

--no-trunc Don't truncate output

-q, --quiet Only show image IDs

Shows the history of the image. This is actually a list of image's layers, and the commands used to create them.

$ docker image history <image_name>:<image_tag>

If image_tag is omitted, latest is used by default.

Another format:

$ docker image history <image_id>

This command is basically reconstructing image's Dockerfile and therefore can be used to find what is this Docker image going to run, what is its base image, what commands make the image large etc...

A tableau of crimes and misfortunes: the ever-useful `docker history`

Example:

% docker history mysql

IMAGE CREATED CREATED BY SIZE COMMENT

7484689f290f 11 days ago /bin/sh -c #(nop) CMD ["mysqld"] 0B

<missing> 11 days ago /bin/sh -c #(nop) EXPOSE 3306 33060 0B

<missing> 11 days ago /bin/sh -c #(nop) ENTRYPOINT ["docker-entry… 0B

<missing> 11 days ago /bin/sh -c ln -s usr/local/bin/docker-entryp… 34B

<missing> 11 days ago /bin/sh -c #(nop) COPY file:e9c22353a1133b89… 14.2kB

<missing> 11 days ago /bin/sh -c #(nop) VOLUME [/var/lib/mysql] 0B

<missing> 11 days ago /bin/sh -c set -eux; microdnf install -y "m… 237MB

<missing> 11 days ago /bin/sh -c #(nop) ENV MYSQL_SHELL_VERSION=8… 0B

<missing> 11 days ago /bin/sh -c set -eu; . /etc/os-release; { … 215B

<missing> 11 days ago /bin/sh -c set -eux; microdnf install -y "m… 178MB

<missing> 11 days ago /bin/sh -c set -eu; . /etc/os-release; { … 225B

<missing> 11 days ago /bin/sh -c #(nop) ENV MYSQL_VERSION=8.0.31-… 0B

<missing> 11 days ago /bin/sh -c #(nop) ENV MYSQL_MAJOR=8.0 0B

<missing> 11 days ago /bin/sh -c set -eux; key='859BE8D7C586F5384… 3.17kB

<missing> 11 days ago /bin/sh -c set -eux; microdnf install -y … 13.6MB

<missing> 11 days ago /bin/sh -c set -eux; arch="$(uname -m)"; c… 2.29MB

<missing> 11 days ago /bin/sh -c #(nop) ENV GOSU_VERSION=1.14 0B

<missing> 11 days ago /bin/sh -c set -eux; groupadd --system --gi… 2.77kB

<missing> 11 days ago /bin/sh -c #(nop) CMD ["/bin/bash"] 0B

<missing> 11 days ago /bin/sh -c #(nop) ADD file:04d9ae26c2acac414… 106MB

To suppress truncating of the commands, we can use --no-trunc:

% docker history --no-trunc mysql

% docker history --no-trunc mysql | grep ENTRYPOINT

<missing> 11 days ago /bin/sh -c #(nop) ENTRYPOINT ["docker-entrypoint.sh"]

docker image inspect

% docker image inspect --help

Usage: docker image inspect [OPTIONS] IMAGE [IMAGE...]

Display detailed information on one or more images

Options:

-f, --format string Format the output using the given Go template

We can use this command to see:

which ports will be exposed in container
which environment variables will be set in container
volumes
command/entrypoint - what will get executed when we run the container
OS and architecture

Example:

% docker image inspect mysql

[

{

"Id": "sha256:7484689f290f1defe06b65befc54cb6ad91a667cf0af59a265ffe76c46bd0478",

"RepoTags": [

"mysql:latest"

"RepoDigests": [

"mysql@sha256:3d7ae561cf6095f6aca8eb7830e1d14734227b1fb4748092f2be2cfbccf7d614"

"Parent": "",

"Comment": "",

"Created": "2022-12-07T02:23:31.34588089Z",

"Container": "39e37396c270e5234472eb14feb4abbdc8212ac30b984481f79756836a2926eb",

"ContainerConfig": {

"Hostname": "39e37396c270",

"Domainname": "",

"User": "",

"AttachStdin": false,

"AttachStdout": false,

"AttachStderr": false,

"ExposedPorts": {

"3306/tcp": {},

"33060/tcp": {}

"Tty": false,

"OpenStdin": false,

"StdinOnce": false,

"Env": [

"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",

"GOSU_VERSION=1.14",

"MYSQL_MAJOR=8.0",

"MYSQL_VERSION=8.0.31-1.el8",

"MYSQL_SHELL_VERSION=8.0.31-1.el8"

"Cmd": [

"/bin/sh",

"-c",

"#(nop) ",

"CMD [\"mysqld\"]"

"Image": "sha256:38354afaf9d5d657e0608e62e7ad59f6b8746d3d6c1776c956f250034041626a",

"Volumes": {

"/var/lib/mysql": {}

"WorkingDir": "",

"Entrypoint": [

"docker-entrypoint.sh"

"OnBuild": null,

"Labels": {}

"DockerVersion": "20.10.12",

"Author": "",

"Config": {

"Hostname": "",

"Domainname": "",

"User": "",

"AttachStdin": false,

"AttachStdout": false,

"AttachStderr": false,

"ExposedPorts": {

"3306/tcp": {},

"33060/tcp": {}

"Tty": false,

"OpenStdin": false,

"StdinOnce": false,

"Env": [

"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",

"GOSU_VERSION=1.14",

"MYSQL_MAJOR=8.0",

"MYSQL_VERSION=8.0.31-1.el8",

"MYSQL_SHELL_VERSION=8.0.31-1.el8"

"Cmd": [

"mysqld"

"Image": "sha256:38354afaf9d5d657e0608e62e7ad59f6b8746d3d6c1776c956f250034041626a",

"Volumes": {

"/var/lib/mysql": {}

"WorkingDir": "",

"Entrypoint": [

"docker-entrypoint.sh"

"OnBuild": null,

"Labels": null

"Architecture": "amd64",

"Os": "linux",

"Size": 538012982,

"VirtualSize": 538012982,

"GraphDriver": {

"Data": {

"LowerDir": "/var/lib/docker/overlay2/166118dbdfd603f6c6a005d36be4ba4d51ef997a6b50d70224208a266f70090e/diff:/var/lib/docker/overlay2/5c6d7d8a1b25af02b5c2bbbe65aceb827e65607d025118f6727c52bd8f7bbc3c/diff:/var/lib/docker/overlay2/8c86f30101e519ae95fff720288754c0685cb000b488243bbca96ad12359001c/diff:/var/lib/docker/overlay2/2b6a8383ab2345fd999f30b75b20ea3e54c96fb13b6c03b0499dfd9fac723bfb/diff:/var/lib/docker/overlay2/493bbbc0b022918b2d463513851deb0357ce094b598a2bb6dc76d4e34be33c19/diff:/var/lib/docker/overlay2/867b29054d700c0d71574adb91e1c28c145082cad242b9ab627c88fec963a8e3/diff:/var/lib/docker/overlay2/04bfc900db8627bc6b346259a0273019508bb7369d573b85a835e42dd3483aa2/diff:/var/lib/docker/overlay2/76f0b8fcc14c3e25dc9470c61f7c2f91324246082c41f408dd39af9725a8a42d/diff:/var/lib/docker/overlay2/33ea513815166ece2e9548d960e5aae3c0ca7acd1ba58cc4143142ff24d6cb72/diff:/var/lib/docker/overlay2/1b45b35a8d681bd00e5c3c59e6353a01267ffc658fa9b173d8a68e957416de10/diff",

"MergedDir": "/var/lib/docker/overlay2/2cf0a924d050e57b34a1a8c5548a48cfb7c2303c156c7c917df0a53e386a2305/merged",

"UpperDir": "/var/lib/docker/overlay2/2cf0a924d050e57b34a1a8c5548a48cfb7c2303c156c7c917df0a53e386a2305/diff",

"WorkDir": "/var/lib/docker/overlay2/2cf0a924d050e57b34a1a8c5548a48cfb7c2303c156c7c917df0a53e386a2305/work"

"Name": "overlay2"

"RootFS": {

"Type": "layers",

"Layers": [

"sha256:d3cc7b6aa7bc15725c1a856ce06fe436da3fbccf0c9c06b04e45f79b3439c154",

"sha256:a7f421510691bf6a7b344d1efb738b3d343e252e7dde114a0dd86d432ef6000c",

"sha256:6ac2db160c6cf3dcf1aff0ced069aa98da28c50cff5cd3c8881c04f42e3ef1fe",

"sha256:7fe65049a2a940ab927d3f5b2cf0687ecffbdf9d7e9df1daaeddb83bc601f3cb",

"sha256:da1824686db37bbf1ffbffea53295aa853731531a14e70bca24eeb6d91fd6327",

"sha256:d410d4efd0e75456011f265fa113b206dd4da9dccf5151bca714ef6c69a3b8cd",

"sha256:60c4dab21dc337e912d518acc56e5b776e3de4f1d277d074831bb678089b87a6",

"sha256:d00057f8969283fed84044f6103036e18a9d776579d705a85472535ba321df25",

"sha256:2f42ce9d7b80a286af13410c0b64e94c90eca3e7597f7fd82a783aa1f68c2373",

"sha256:8408fed6a9d685236cb024ceea39692743b6c52ea6c4c068b22a6475f742e24a",

"sha256:336175ddf157a8f50c0aae8c0726b1462fd41f30f0b7f84caf6bf5cd02f8de77"

]

"Metadata": {

"LastTagTime": "0001-01-01T00:00:00Z"

}

]

docker image ls

$ docker image ls --help

Usage: docker image ls [OPTIONS] [REPOSITORY[:TAG]]

List images

Aliases:
ls, images, list

Options:
-a, --all Show all images (default hides intermediate images)
--digests Show digests
-f, --filter filter Filter output based on conditions provided
--format string Pretty-print images using a Go template
--no-trunc Don't truncate output
-q, --quiet Only show numeric IDs

To list all images:

$ docker image ls

$ docker images

Example:

% docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

mysql latest 7484689f290f 11 days ago 538MB

in28min/hello-world-python 0.0.1.RELEASE 6d1dfe87a934 6 months ago 91MB

% docker image ls

REPOSITORY TAG IMAGE ID CREATED SIZE

mysql latest 7484689f290f 11 days ago 538MB

in28min/hello-world-python 0.0.1.RELEASE 6d1dfe87a934 6 months ago 91MB

To list IDs of all images:

$ docker image ls -aq

docker image rm (docker image remove)

Removes an image from the local machine.

$ docker image rm --help

Usage: docker image rm [OPTIONS] IMAGE [IMAGE...]

Remove one or more images

Aliases:
rm, rmi, remove

Options:
-f, --force Force removal of the image
--no-prune Do not delete untagged parents

To remove some image:

$ docker image rm <image_id>

$ docker image rm <image_name>:<image_label>

To delete all images:

$ docker image rm $(docker image ls -aq)

Image can't be removed if it's referenced by some container. We first need to remove the container:

$ docker container rm <container_id>

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