Cannot install packages inside docker Ubuntu image

I installed Ubuntu 14.04 image on docker. After that, when I try to install packages inside the ubuntu image, I'm getting unable to locate package error:

apt-get install curl

Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package curl

How to fix this error?

It is because there is no package cache in the image, you need to run:

apt-get update

before installing packages, and if your command is in a Dockerfile, you'll then need:

apt-get -y install curl

To suppress the standard output from a command use -qq. E.g.

apt-get -qq -y install curl

From the docs in May 2017 2018 2019 2020 2021

Always combine RUN apt-get update with apt-get install in the same RUN statement, for example

RUN apt-get update && apt-get install -y package-bar

(...)

Using apt-get update alone in a RUN statement causes caching issues and subsequent apt-get install instructions fail.

(...)

Using RUN apt-get update && apt-get install -y ensures your Dockerfile installs the latest package versions with no further coding or manual intervention. This technique is known as “cache busting”.

Add following command in Dockerfile:

RUN apt-get update