Overview

For the past year it seems, everyone is trying Docker, running processes in containers to make environments more predictable and reproducable. However old habits die hard, and once again I see installations that are far larger with wasted resources at best, and insecure, unused services running at worst. Most people running Docker are using huge images with needless applications installed and taking up space for their containers. Meanwhile, if you search in the Docker Registry for ‘debian minimal’ you’ll come across some images that are over 260 MB! Whenever I build a new server I install Debian/GNU Linux doing a Network install from a minimal CD which only includes the minimal base OS. My goal is to recreate this for Docker, starting with a base Debian install, and then removing things in that minimal install that are not needed by Docker, while leaving the basic *nix utilities in place. After this I use docker-squash tool to free a few more bits in the container before committing and checking in the image here.

Usage

If you just want to use this image, pull it and configure what you want:

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docker pull philcryer/min-wheezy

To use this image in your own project, use this FROM line in your Dockerfile:

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FROM philcryer/min-wheezy:latest

Build

In the interest of Open Source and transparency, here are the steps I’ve taken to build this image.

Pull the official base Debian Wheezy image

_See Debian Official Docker page for information on this container_

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docker pull debian:wheezy

Get the image ID and run the container

Notice how small it is to start with

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# docker images | tail -n1
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debian                      wheezy              f6fab3b798be        4 weeks ago          85.1 MB
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# docker run -it f6fab3b798be /bin/bash

Inside the container, run the following

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apt-get update && apt-get upgrade -y
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apt-get clean -y && apt-get autoclean -y && apt-get autoremove -y
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cp -R /usr/share/locale/en\@* /tmp/ && rm -rf /usr/share/locale/* && mv /tmp/en\@* /usr/share/locale/
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rm -rf /var/cache/debconf/*-old && rm -rf /var/lib/apt/lists/* && rm -rf /usr/share/doc/*
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echo "`cat /etc/issue.net` Docker Image - philcryer/min-wheezy - `date +'%Y/%m/%d'`" > /etc/motd
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exit

Commit those changes

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# docker ps -a | head -n2
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CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                      PORTS               NAMES
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9fd99c47de64        debian:wheezy       "/bin/bash"         3 minutes ago       Exited (0) 12 seconds ago                       insane_newton
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# docker commit  9fd99c47de64
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3dd7dab3803b2bb507a576119ac3daf3de9f700cbf0e80127acc04a85891c0d4

Squash the image and get its new ID

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# docker save 3dd7dab380 | docker-squash -from root -t philcryer/min-wheezy | docker load
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# docker images | head -n2
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REPOSITORY             TAG                 IMAGE ID            CREATED              VIRTUAL SIZE
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philcryer/min-wheezy   latest              243925c5b6ed        12 seconds ago       50.76 MB

Push it to the Docker registry

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docker push philcryer/min-wheezy

Results

Pull the image and check the size:

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# docker pull philcryer/min-wheezy:latest
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Pulling repository philcryer/min-wheezy
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243925c5b6ed: Download complete
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511136ea3c5a: Download complete
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dbb9d41e1af3: Download complete
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Status: Downloaded newer image for philcryer/min-wheezy:latest
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# docker images
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REPOSITORY             TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
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philcryer/min-wheezy   latest              243925c5b6ed        2 minutes ago       50.76 MB

Container details

Just for reference, this Docker container will contain the following.

Kernel

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# uname -a
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Linux cbfd8af55155 3.16.0-4-amd64 #1 SMP Debian 3.16.7-2 (2014-11-06) x86_64 GNU/Linux

Installed packages

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# dpkg --get-selections
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apt           install
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base-files          install
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base-passwd         install
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bash            install
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bsdutils          install
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coreutils         install
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dash            install
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debconf           install
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debconf-i18n          install
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debian-archive-keyring        install
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debianutils         install
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diffutils         install
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dpkg            install
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e2fslibs:amd64          install
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e2fsprogs         install
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findutils         install
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gcc-4.7-base:amd64        install
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gnupg           install
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gpgv            install
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grep            install
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gzip            install
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hostname          install
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inetutils-ping          install
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initscripts         install
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insserv           install
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iproute           install
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libacl1:amd64         install
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libapt-pkg4.12:amd64        install
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libattr1:amd64          install
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libblkid1:amd64         install
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libbz2-1.0:amd64        install
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libc-bin          install
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libc6:amd64         install
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libcomerr2:amd64        install
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libdb5.1:amd64          install
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libgcc1:amd64         install
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liblocale-gettext-perl        install
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liblzma5:amd64          install
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libmount1         install
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libncurses5:amd64       install
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libpam-modules:amd64        install
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libpam-modules-bin        install
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libpam-runtime          install
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libpam0g:amd64          install
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libreadline6:amd64        install
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libselinux1:amd64       install
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libsemanage-common        install
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libsemanage1:amd64        install
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libsepol1:amd64         install
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libslang2:amd64         install
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libss2:amd64          install
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libstdc++6:amd64        install
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libtext-charwidth-perl        install
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libtext-iconv-perl        install
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libtext-wrapi18n-perl       install
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libtinfo5:amd64         install
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libusb-0.1-4:amd64        install
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libustr-1.0-1:amd64       install
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libuuid1:amd64          install
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login           install
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lsb-base          install
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mawk            install
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mount           install
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multiarch-support       install
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ncurses-base          install
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ncurses-bin         install
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netbase           install
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passwd            install
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perl-base         install
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readline-common         install
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sed           install
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sensible-utils          install
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sysv-rc           install
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sysvinit          install
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sysvinit-utils          install
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tar           install
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tzdata            install
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util-linux          install
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xz-utils          install
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zlib1g:amd64          install

Feedback

This is one of my first Docker images (see all of them here) so please give me feedback in the comments. Thanks!

HOWTO build tiny docker images