[docker] 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?

Add following command in Dockerfile:

RUN apt-get update

From the docs in May 2017 2018 2019 2020

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”.

I found that mounting a local volume over /tmp can cause permission issues when the "apt-get update" runs, which prevents the package cache from being populated. Hopefully, this isn't something most people do, but it's something else to look for if you see this issue.

You need to update the package list in your Ubuntu:

$ sudo apt-get update
$ sudo apt-get install <package_name>

Make sure you don't have any syntax errors in your Dockerfile as this can cause this error as well. A correct example is:

RUN apt-get update \
    && apt-get -y install curl \
    another-package

It was a combination of fixing a syntax error and adding apt-get update that solved the problem for me.