Docker Engine

Brief

Docker engine is containerization technology.

Uses:

• namespaces
• cgroups

More information in Official documentation

Tips

Clean apt cache in due build process

FROM ubuntu:latest

RUN apt update \
    && apt install -y curl unzip \
    && rm -rf /var/lib/apt/lists/* \
    && apt clean

How to pass secret in build process

💡 That secrets will not be store in an image. Secret will not available after build process.

• Make sure env DOCKER_BUILDKIT defined.
• Secret available in the mounted step others steps cannot reach secret.

$ export DOCKER_BUILDKIT=1
$ docker build --secret  id=secretfile,src=<secret_path> .

Other way running as:

$ DOCKER_BUILDKIT=1 docker build --secret  id=secretfile,src=<secret_path> .

Example Dockerfile:

FROM ubuntu:latest

RUN --mount=type=secret,id=secretfile,dst=/<home_dir>/.ssh/id_rsa \
    git clone git://<target_repo_with_ssh>/<name_of_repo>.git

Save stdout log from container

$ docker logs <container_name> > <filename_log> 2>&1

Check history of image

$ docker history <image_id>

Copy all data from container

$ docker export <container_id> > <name_of_tar>

Check runtime metrics

$ docker stats

Enable full access from container to GuestOS

This is UNSECURE

$ docker run -ti --privilage <image>

Copy images between two different registries

$ docker save <DOCKER_IMAGE> | gzip | pv | DOCKER_HOST=ssh://<username>@<target_host>:<target_port> docker load