Docker: How to Create Your Own Base Image (CentOS/RHEL)

Normally, we will pull base images from the Docker Hub registry to build our own images.

However, there might be times when you want more control over the base image (size, packages, etc.). Luckily, Docker provides a way to do that.

For general information about building your own image, refer here. Since I am a fan of CentOS/RHEL, I would normally go here. For a more "friendly" version of the script, go here.

To create your own CentOS/RHEL image, follow these instructions:
(1) Copy or download the script to a running CentOS/RHEL system with yum properly setup. 
NOTE: I tested the script on CentOS 6.5.

#!/usr/bin/env bash # # Create a base CentOS Docker image. # # This script is useful on systems with yum installed (e.g., building # a CentOS image on CentOS). See contrib/mkimage-rinse.sh for a way # to build CentOS images on other systems. usage() { cat <<EOOPTS OPTIONS: -y <yumconf> The path to the yum config to install packages from. The default is /etc/yum.conf. EOOPTS exit 1 } # option defaults yum_config=/etc/yum.conf while getopts ":y:h" opt; do case $opt in y) yum_config=$OPTARG ;; h) usage ;; \?) echo "Invalid option: -$OPTARG" usage ;; esac done shift $((OPTIND - 1)) name=$1 if [[ -z $name ]]; then usage fi #-------------------- target=$(mktemp -d --tmpdir $(basename $0).XXXXXX) set -x mkdir -m 755 "$target"/dev mknod -m 600 "$target"/dev/console c 5 1 mknod -m 600 "$target"/dev/initctl p mknod -m 666 "$target"/dev/full c 1 7 mknod -m 666 "$target"/dev/null c 1 3 mknod -m 666 "$target"/dev/ptmx c 5 2 mknod -m 666 "$target"/dev/random c 1 8 mknod -m 666 "$target"/dev/tty c 5 0 mknod -m 666 "$target"/dev/tty0 c 4 0 mknod -m 666 "$target"/dev/urandom c 1 9 mknod -m 666 "$target"/dev/zero c 1 5 yum -c "$yum_config" --installroot="$target" --releasever=/ --setopt=tsflags=nodocs \ --setopt=group_package_types=mandatory -y groupinstall Core yum -c "$yum_config" --installroot="$target" -y clean all cat > "$target"/etc/sysconfig/network <<EOF NETWORKING=yes HOSTNAME=localhost.localdomain EOF # effectively: febootstrap-minimize --keep-zoneinfo --keep-rpmdb # --keep-services "$target". Stolen from mkimage-rinse.sh # locales rm -rf "$target"/usr/{{lib,share}/locale,{lib,lib64}/gconv,bin/localedef,sbin/build-locale-archive} # docs rm -rf "$target"/usr/share/{man,doc,info,gnome/help} # cracklib rm -rf "$target"/usr/share/cracklib # i18n rm -rf "$target"/usr/share/i18n # sln rm -rf "$target"/sbin/sln # ldconfig rm -rf "$target"/etc/ld.so.cache rm -rf "$target"/var/cache/ldconfig/* version= if [ -r "$target"/etc/redhat-release ]; then version="$(sed 's/^[^0-9\]*\([0-9.]\+\).*$/\1/' "$target"/etc/redhat-release)" fi if [ -z "$version" ]; then echo >&2 "warning: cannot autodetect OS version, using '$name' as tag" version=$name fi tar --numeric-owner -c -C "$target" . | docker import - $name:$version docker run -i -t $name:$version echo success rm -rf "$target"

(2) Save the script and give it execute permission (chmod 700 <script>).

(3) Login as 'root'.

(4) Amend the script as necessary to suit your purpose (eg. more packages, etc).

(5) Execute the script (eg. createDockerImage.sh centos).
WHERE "centos" is the name that you would like the resultant image to have
NOTE: The script will tag the image using the version of the OS (or the "name" provided if the version cannot be determined).

(6) Once the script returns, run "docker images" to confirm the image is created.

(7) Verify that the image is ok by launching a container using "docker run -t -i <image> /bin/bash".

If everything works out fine, you would now have your custom built base image!