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Create sudoer user in docker

RUN apt-get update && apt-get install -y sudo && rm -rf /var/lib/apt/lists/*
RUN useradd -m user && \
    echo "user ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/user && \
    chmod 0400 /etc/sudoers.d/gitlab
USER user

Docker save, load

Documents:

Save one or more images to a tar archive (streamed to STDOUT by default)

$ docker save -o etcd_v3.2.9.tar gcr.io/etcd-development/etcd:v3.2.9
$ docker load -i etcd_v3.2.9.tar

It is very useful when docker pull command hangs downloading image

Multi-stage build

# base image
FROM microsoft/dotnet:2.1-runtime AS base
WORKDIR /app
EXPOSE 80

# build image
FROM microsoft/dotnet:2.1-sdk AS build
WORKDIR /src
COPY . .
# `dotnet publish` command will run `dotnet restore` and `dotnet build` implicitly
RUN dotnet publish -c Release -o /app

# Add the binary files that generated in the `build image` container above
FROM base as final
WORKDIR /app
COPY --from=build /app .
RUN ls -al
ENTRYPOINT ["dotnet", "OrleansSilo.dll"]

Set build-time variables (--build-arg)

Dockerfile:

FROM ubuntu
ARG MESSAGE
RUN echo $MESSAGE

Command:

$ docker build --build-arg MESSAGE=hello .

Use ARG with ENV

ARG <name>[=<default value>]

You can use an ARG or an ENV instruction to specify variables that are available to the RUN instruction. Environment variables defined using the ENV instruction always override an ARG instruction of the same name. Consider this Dockerfile with an ENV and ARG instruction.

Dockerfile:

FROM ubuntu
ARG CONT_IMG_VER
ENV CONT_IMG_VER v1.0.0
RUN echo $CONT_IMG_VER

Command:

$ docker build --build-arg CONT_IMG_VER=v2.0.1 .

In this case, the RUN instruction uses v1.0.0 instead of the ARG setting passed by the user: v2.0.1

references: