Dockerfile

A Dockerfile is a file containing all the instructions needed to build an image

A simple Dockerfile

Create a file with the name Dockerfile
```
nano Dockerfile
```
and add these two lines to the file:
```
FROM debian:12
ENTRYTPOINT "echo" "Hello, World!"
```
An image can be built from this Dockerfile with the command

docker build <directory containing the Dockerfile> -t <tag>
```
docker build . -t if3-hello-world
```

All available images can be seen using docker image ls

$ docker image ls
REPOSITORY        TAG       IMAGE ID       CREATED          SIZE
if3-hello-world   latest    128a133d9ac4   11 minutes ago   117MB
debian            12        676aedd4776f   2 weeks ago      117MB

A container can be created and started with docker run ...
```
$ docker run if3-hello-world
Hello, World!
```

Simple, but in style - another Dockerfile

Edit the Dockerfile like below

FROM debian:12
-ENTRYPOINT "echo" "Hello, World!"
+RUN apt-get update
+RUN apt-get install figlet -y
+ENTRYPOINT "figlet" "Hello, World!"

Save the file and build a new image. Let's call the new image if3-hello-world-figlet
```
docker build . -t if3-hello-world-figlet
```

Start a container with the new image

$ docker run if3-hello-world-figlet
 _   _      _ _         __        __         _     _ _ 
| | | | ___| | | ___    \ \      / /__  _ __| | __| | |
| |_| |/ _ \ | |/ _ \    \ \ /\ / / _ \| '__| |/ _` | |
|  _  |  __/ | | (_) |    \ V  V / (_) | |  | | (_| |_|
|_| |_|\___|_|_|\___( )    \_/\_/ \___/|_|  |_|\__,_(_)
                    |/