Create Images

Question 1

what are FROM scratch and FROM ParentImage?

Answer 1

FROM scratch is used to create a Base Image and the other is to create and image From ParentImage

https://docs.docker.com/build/building/base-images/

Question 2

What is a Base Image?

Answer 2

A base image has no parent image specified in its Dockerfile. It is created using a Dockerfile with the FROM scratch directive.

https://docs.docker.com/glossary/#base-image

Question 3

What is a Parent Image?

Answer 3

An image’s parent image is the image designated in the FROM directive in the image’s Dockerfile

https://docs.docker.com/glossary/#parent-image

Question 4

What is RUN <command> instruction?

Answer 4

Executes any commands in a new layer on top of the current image and commits the result.

https://docs.docker.com/build/building/packaging/

Question 5

What is From <image> instruction?

Answer 5

Defines a base for your image.

https://docs.docker.com/build/building/packaging/

Question 6

What is WORKDIR <directory> instruction?

Answer 6

Sets the working directory for any RUN, CMD, ENTRYPOINT, COPY, and ADD instructions that follow it in the Dockerfile.

https://docs.docker.com/build/building/packaging/

Question 7

What is COPY <src> <dest> instruction?

Answer 7

Copies new files or directories from <src> and adds them to the filesystem of the container at the path <dest>.

https://docs.docker.com/build/building/packaging/

Question 8

What is CMD <command>instruction?

Answer 8

Lets you define the default program that is run once you start the container based on this image

https://docs.docker.com/build/building/packaging/

Question 9

what is ARG <name>[=<default value>] instruction?

Answer 9

The ARG instruction defines a variable that users can pass at build-time to the builder with the docker build command using the --build-arg <varname>=<value> flag

https://docs.docker.com/engine/reference/builder/#arg

Question 10

Which istruction is first From or ARG?

Answer 10

FROM

Question 11

Is Possible to set a defaul value on a ARG instruction.

Answer 11

YES
ARG var_name=<def value>

Question 12

Wha is LABEL <key>=<value> <key>=<value> <key>=<value> ... instruction?

Answer 12

The LABEL instruction adds metadata to an image

https://docs.docker.com/engine/reference/builder/#label:~:text=LABEL-,%F

Question 13

What is ADD [--chown=<user>:<group>] [--checksum=<checksum>] <src>... <dest> instruction?

Answer 13

The ADD instruction copies new files, directories or remote file URLs from <src> and adds them to the filesystem of the image at the path <dest>.

https://docs.docker.com/engine/reference/builder/#add:~:text=ENV-,ADD,-V

Question 14

what is COPY in Dockerfile command. [--chown=<user>:<group>] <src>... <dest> instruction?

Answer 14

The COPY instruction copies new files or directories from <src> and adds them to the filesystem of the container at the path <dest>.

https://docs.docker.com/engine/reference/builder/#copy:~:text=COPY-,%F0%

Question 15

What is ENTRYPOINT ["executable", "param1", "param2"] instruction?

Answer 15

An ENTRYPOINT allows you to configure a container that will run as an executable.

+ ENTRYPOINT ["executable", "param1", "param2"]
+ ENTRYPOINT command param1 param2

https://docs.docker.com/engine/reference/builder/#entrypoint

Question 16

What is EXPOSE <port> [<port>/<protocol>...] instruction?

Answer 16

The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime.

The default protocol is TCP if the protocol is not specified.

It create a Metadata but not a layer into the image

https://docs.docker.com/engine/reference/builder/#expose:~:text=MAINTAIN

Question 17

What is the command to build an image from a Dockerfile

Answer 17

+ docker image build [OPTIONS] PATH|URL
+ docker build [OPTIONS] PATH|URL

On PATH , you ca use . to set the current directory where Dockerfile is.

Question 18

How can we set a name and tag at building time of an Image?

Answer 18

using the flag -t

+ docker image build -t <name>:<tag>
+ docker build -t <name>:<tag>

docker build –help

Question 19

What is the command to login to Dockers?

Answer 19

docker login

After that, user and password shall be required.

Question 20

What is the command to tag an Image?

Answer 20

docker image tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]

Where:
+ SOURCE_IMAGE[:TAG] is the name set on build commando with the flag -t.
+ TARGET_IMAGE[:TAG] is the full name that MUST include the Docker ID i.e:

docker image tag web:latest nigelpoulton/web:latest

You Must be logget.

Question 21

What is the command to publish an image?

Answer 21

docker image push TARGET_IMAGE[:TAG]

+ TARGET_IMAGE[:TAG] is the full name that MUST include the Docker ID i.e:

docker image push nigelpoulton/web:latest

You Must be logget.

Question 22

What do you need to create an Linux Base Image (scratch)?

Answer 22

It’s necessary to know the basic package to add to have the basic functionality.

For example, for linux:
```cmd
FROM scratch
ADD ubuntu-kinetic-oci-amd64-root.tar.gz /
CMD [“bash”]
~~~

Manjaro linux:
```cmd
FROM scratch
ADD manjaro.tar /
ENV LANG=en_US.UTF-8
CMD [“/usr/bin/bash”]
~~~

Question 23

What are VOLUMES?

Answer 23

volumes defines mount host paths or named volumes that MUST be accessible by service containers.

+ Volumes are the preferred mechanism for persisting data generated by and used by Docker containers.
+ They are complete managed by DOcker

https://docs.docker.com/storage/volumes/
https://docs.docker.com/compose

Question 24

What is the basic structure to declare a VOLUME and what is its function?

Answer 24

<Local File Systema Path>:<Containte Mount Path>

Mapping a local directories into Container

https://docs.docker.com/storage/volumes/#start-a-container-with-a-volume

https://docs.docker.com/compose/compose-file/#volumes

Question 25

What is the command to celar all unusued data un docker?

Answer 25

docker system prune

YOU MUST USED THIS COMMAND CAREFULLY!

Question 26

How to list all the volumes created?

Answer 26

docker volume ls

Question 27

How to remove all volumes in docker?

Answer 27

docker volume prune