How to write Dockerfile for installing packages

Install git, gradle and openjdk 11

Using Ubuntu as base image

FROM ubuntu:latest

RUN apt update && apt install -y --no-install-recommends 
    git 
    wget 
    openjdk-11-jdk 
    gradle 
    && rm -rf /var/lib/apt/lists/*

Using Centos as base image

FROM centos:latest

ENV PATH=$PATH:/opt/gradle/gradle-7.0.2/bin

RUN yum update -y && yum install -y 
    git 
    wget 
    unzip 
    java-11-openjdk-devel 
    && yum clean all

RUN mkdir /opt/gradle 
    && wget -q https://services.gradle.org/distributions/gradle-7.0.2-bin.zip 
    && unzip gradle-7.0.2-bin.zip -d /opt/gradle/ 
    && rm -f gradle-7.0.2-bin.zip

Using Alpine as base image

FROM alpine:latest

ENV PATH=$PATH:/opt/gradle/gradle-7.0.2/bin

RUN apk add --no-cache 
    git 
    openjdk11

RUN mkdir /opt/gradle 
    && wget -q https://services.gradle.org/distributions/gradle-7.0.2-bin.zip 
    && unzip gradle-7.0.2-bin.zip -d /opt/gradle/ 
    && rm -f gradle-7.0.2-bin.zip

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Important Tips

Tip

Clean Up: Always clean up package manager caches (e.g., rm -rf /var/lib/apt/lists/*, yum clean all) in the same RUN instruction to keep the image size small.

Note

No Cache: For Alpine Linux, use apk add --no-cache. This installs the package and cleans up the cache in a single step, eliminating the need for a separate rm command.

🧠 Quick Quiz — Package Management

#

Which command is used to install packages in an Ubuntu-based Docker image?

apt install

yum install

apk add

brew install

Ubuntu and Debian use the apt (Advanced Package Tool) package manager.

#

Why do we use && to chain commands in a Dockerfile?

To execute multiple commands in a single layer.

To run commands in parallel.

To make the build slower.

It's a typo.

Chaining commands ensures that temporary files created and deleted within the same Run instruction don't permanently increase the image size.

#

What is the package manager for Alpine Linux?

apk

apt

yum

dnf

Alpine Linux uses apk (Alpine Package Keeper), which is known for being fast and lightweight.

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