1. Build a container using Docker for cmatrix screensaver - Alpine

Prerequisites

• Docker

Assignment

• Lets build a container using the github repository created for running a Matrix screensaver.
• Languages: C

1. Pull a base docker image ‘alpine’ - Ultrasmall and minimal image based on alpine linux (size: ~8MB)

docker pull alpine

1. Verify if the images exists on your host

docker images

1. Create a Dockerfile using the apline images

cat <<EOF> ./Dockerfile
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde"
EOF

1. Build a docker image using the Dockerfile (Same as base image with just additional label)

docker build -t sakharamshinde/cmatrix .

1. Verify if the new images is created with the defined tag.

docker images

1. Create a container using the new image and ssh into the container

docker run --rm -it sakharamshinde/cmatrix sh

1. Once we are into the shell of the container, execute below steps to get the cmatrix running inside the container.

• Verify the Hostname

hostname

• Clone the Repository, this will fail

git clone https://github.com/abishekvashok/cmatrix.git

1. Since git is not installed in the base image, we will install the git tool.

apk update

apk add git

• Clone the repo

git clone https://github.com/abishekvashok/cmatrix.git

• Switch to the repo dir and check the contents

cd cmatrix

ls -l 

1. Similarly, install the required packages required to build the cmatrix screensave

• Prepare compilation, will fail, missing autoconf

autoreconf -i

• Install autoconf

apk add autoconf

• Prepare compilation, will fail, missing automake

autoreconf -i

• Install automake

apk add automake

• Prepare compilation, will succeed, confirm with echo $?

autoreconf -i

• Verify it the install was successful

echo $?

• Prepare configure, will fail, missing compiler

./configure LDFLAGS="-static"

• Install compiler

apk add alpine-sdk

• Prepare configure, will fail, missing dependencies

./configure LDFLAGS="-static"

• Install dependencies and create missing directories

apk add ncurses-dev ncurses-static

mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts

• Prepare configure, will succeed

./configure LDFLAGS="-static"

• Compile and view result

make

• Check the created binary

ls -l ./cmatrix

• Run cmatrix

./cmatrix

1. Build a docker image for the cmatrix app using all the command used above.

cat <<EOF> ./Dockerfile
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde"

RUN apk update

RUN apk add git 

RUN git clone https://github.com/abishekvashok/cmatrix.git .

RUN cd cmatrix

RUN apk add autoconf

RUN apk add automake

RUN autoreconf -i

RUN apk add alpine-sdk

RUN apk add ncurses-dev ncurses-static

RUN mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts

RUN ./configure LDFLAGS="-static"

RUN make

CMD ["./cmatrix"]

EOF

• Build a new image with the updated Dockerfile

docker build -t sakharamshinde/cmatrix .

• Run the new image, this will fail

docker run --rm -it sakharamshinde/cmatrix

• Specify the working directory for the Dockerfile

cat <<EOF> ./Dockerfile
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde"

WORKDIR /cmatrix

RUN apk update

RUN apk add git 

RUN git clone https://github.com/abishekvashok/cmatrix.git .

RUN apk add autoconf

RUN apk add automake

RUN autoreconf -i

RUN apk add alpine-sdk

RUN apk add ncurses-dev ncurses-static

RUN mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts

RUN ./configure LDFLAGS="-static"

RUN make

CMD ["./cmatrix"]

EOF

• Build a new image with the updated Dockerfile

docker build -t sakharamshinde/cmatrix .

• Run the new image, this will succeed

docker run --rm -it sakharamshinde/cmatrix

1. Check the size of the new image and inspect the layers

docker images

docker history sakharamshinde/cmatrix

1. To reduce the number of layers, we will combine common commands into one

cat <<EOF> ./Dockerfile
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde"

WORKDIR /cmatrix

RUN apk update --no-cache && \
    apk add git autoconf automake alpine-sdk ncurses-dev ncurses-static
    
RUN git clone https://github.com/abishekvashok/cmatrix.git .

RUN autoreconf -i

RUN mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts

RUN ./configure LDFLAGS="-static"

RUN make

CMD ["./cmatrix"]

EOF

• Build the image

docker build -t sakharamshinde/cmatrix .

• Run the new image

docker run --rm -it sakharamshinde/cmatrix

1. Check the size of the image and inspect the layers

docker images

docker history sakharamshinde/cmatrix

1. To reduce the size further, we can combine all the RUN commands

cat <<EOF> ./Dockerfile
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde"

WORKDIR /cmatrix

RUN apk update --no-cache && \
apk add git autoconf automake alpine-sdk ncurses-dev ncurses-static && \
git clone https://github.com/abishekvashok/cmatrix.git . && \
autoreconf -i && \
mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts && \
./configure LDFLAGS="-static" && \
make

CMD ["./cmatrix"]

EOF

• Build the image

docker build -t sakharamshinde/cmatrix .

• Run the new image

docker run --rm -it sakharamshinde/cmatrix

1. Check the size of the image and inspect the layers

docker images

docker history sakharamshinde/cmatrix

1. Build the image using multi-stage docker build

cat <<EOF> ./Dockerfile
# Build Container Image
FROM alpine AS cmatrixbuilder 

WORKDIR /cmatrix

RUN apk update --no-cache && \
    apk add git autoconf automake alpine-sdk ncurses-dev ncurses-static && \
    git clone https://github.com/abishekvashok/cmatrix.git . && \
    autoreconf -i && \
    mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts && \
    ./configure LDFLAGS="-static" && \
    make

# cmatrix Container Image
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde" \

RUN apk update --no-cache && \
    apk add ncurses-terminfo-base

COPY --from=cmatrixbuilder /cmatrix/cmatrix /cmatrix

CMD ["./cmatrix"]

EOF

• Build the image

docker build -t sakharamshinde/cmatrixms .

• Run the new image

docker run --rm -it sakharamshinde/cmatrixms

1. Check the user running the container

docker run --rm -it sakharamshinde/cmatrixms whoami

1. Run the container as a user instead of root

cat <<EOF> ./Dockerfile
# Build Container Image
FROM alpine AS cmatrixbuilder 

WORKDIR /cmatrix

RUN apk update --no-cache && \
    apk add git autoconf automake alpine-sdk ncurses-dev ncurses-static && \
    git clone https://github.com/abishekvashok/cmatrix.git . && \
    autoreconf -i && \
    mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts && \
    ./configure LDFLAGS="-static" && \
    make

# cmatrix Container Image
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde" \

RUN apk update --no-cache && \
    apk add ncurses-terminfo-base && \
    adduser -g "Sakharam" -s /usr/sbin/nologin -D -H sakharam

COPY --from=cmatrixbuilder /cmatrix/cmatrix /cmatrix

USER sakharam
CMD ["./cmatrix"]
EOF

• Build the image

docker build -t sakharamshinde/cmatrixms .

• Run the new image

docker run --rm -it sakharamshinde/cmatrixms

1. Run the container with entrpoint and commands

cat <<EOF> ./Dockerfile
# Build Container Image
FROM alpine AS cmatrixbuilder 

WORKDIR /cmatrix

RUN apk update --no-cache && \
    apk add git autoconf automake alpine-sdk ncurses-dev ncurses-static && \
    git clone https://github.com/abishekvashok/cmatrix.git . && \
    autoreconf -i && \
    mkdir -p /usr/lib/kbd/consolefonts /usr/share/consolefonts && \
    ./configure LDFLAGS="-static" && \
    make

# cmatrix Container Image
FROM alpine

LABEL org.opencontainers.image.authors="Sakharam Shinde" \

RUN apk update --no-cache && \
    apk add ncurses-terminfo-base && \
    adduser -g "Sakharam" -s /usr/sbin/nologin -D -H sakharam

COPY --from=cmatrixbuilder /cmatrix/cmatrix /cmatrix

USER sakharam
ENTRYPOINT ["./cmatrix"]
CMD ["-b"]

EOF

• Build the image

docker build -t sakharamshinde/cmatrixms .

• Run the new image

docker run --rm -it sakharamshinde/cmatrixms --help