Creating a docker Base Image

Question

I have a private Linux distribution (based on redhat7). I have an ISO file which holds the installation of that distribution, which can be used to install the OS on a clear system only. I have some programs I would like to run as images on docker, each program on a different image. Each program can only run on my Linux environment and so I am looking for a way to create the appropriate images, so they can be ran under docker.

I tried following Solomon instructions here:

mkdir rootfs
mount -o loop /path/to/iso rootfs
tar -C rootfs -c . | docker import - rich/mybase

But I don't know how to proceed. I can't run any command since the machine isn't running yet (no /bin/bash/ etc.) How can I open the installation shell?

Is there a better way to run programs via docker on a private Linux distribution? (Just to be clear, the programs can run only on that specific OS and that OS can only be installed on a clear machine. Not sure if I need a base image but I'd like to run these programs with Docker and that is possible only over this OS)

I ran into many questions like mine (like this) but I couldn't find answer that helped me.

Try installing the installation on an empty (non-docker) VM with kvm or virtualbox. This can be done with a fresh VM by mounting the installation media as a cdrom drive. Then tar up this system and use as the tarball in the `docker import` step. — Paul, Apr 25 '16 at 23:45

score 0 · Accepted Answer · answered Apr 25 '16 at 14:09

Assumption

Server A where the ISO will be mount Server R your private repositoy Server N where container will be run All server can connect to server R.

How to

build a base image as mentioned in your OP (named base/myimage)
Push the image to your private repository https://docs.docker.com/registry/deploying/
Create application images from your base base/myimage then push them to your private repo
From Server N, run the application image

docker run application/myapp

score 0 · Answer 2 · answered Apr 25 '16 at 23:40

This script is from the official Docker contrib repo. It's used to create CentOS images from scratch. It should work with any Redhat/Centos based system and gives you plenty of control over the various steps. Anything beyond that you can then modify post-base-image through a Dockerfile.

The file is here

#!/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
$(basename $0) [OPTIONS] <name>
OPTIONS:
  -p "<packages>"  The list of packages to install in the container.
                   The default is blank.
  -g "<groups>"    The groups of packages to install in the container.
                   The default is "Core".
  -y <yumconf>     The path to the yum config to install packages from. The
                   default is /etc/yum.conf for Centos/RHEL and /etc/dnf/dnf.conf for Fedora
EOOPTS
    exit 1
}

# option defaults
yum_config=/etc/yum.conf
if [ -f /etc/dnf/dnf.conf ] && command -v dnf &> /dev/null; then
    yum_config=/etc/dnf/dnf.conf
    alias yum=dnf
fi
install_groups="Core"
while getopts ":y:p:g:h" opt; do
    case $opt in
        y)
            yum_config=$OPTARG
            ;;
        h)
            usage
            ;;
        p)
            install_packages="$OPTARG"
            ;;
        g)
            install_groups="$OPTARG"
            ;;
        \?)
            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

# amazon linux yum will fail without vars set
if [ -d /etc/yum/vars ]; then
    mkdir -p -m 755 "$target"/etc/yum
    cp -a /etc/yum/vars "$target"/etc/yum/
fi

if [[ -n "$install_groups" ]];
then
    yum -c "$yum_config" --installroot="$target" --releasever=/ --setopt=tsflags=nodocs \
        --setopt=group_package_types=mandatory -y groupinstall $install_groups
fi

if [[ -n "$install_packages" ]];
then
    yum -c "$yum_config" --installroot="$target" --releasever=/ --setopt=tsflags=nodocs \
        --setopt=group_package_types=mandatory -y install $install_packages
fi

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 "$target".
#  locales
rm -rf "$target"/usr/{{lib,share}/locale,{lib,lib64}/gconv,bin/localedef,sbin/build-locale-archive}
#  docs and man pages
rm -rf "$target"/usr/share/{man,doc,info,gnome/help}
#  cracklib
rm -rf "$target"/usr/share/cracklib
#  i18n
rm -rf "$target"/usr/share/i18n
#  yum cache
rm -rf "$target"/var/cache/yum
mkdir -p --mode=0755 "$target"/var/cache/yum
#  sln
rm -rf "$target"/sbin/sln
#  ldconfig
rm -rf "$target"/etc/ld.so.cache "$target"/var/cache/ldconfig
mkdir -p --mode=0755 "$target"/var/cache/ldconfig

version=
for file in "$target"/etc/{redhat,system}-release
do
    if [ -r "$file" ]; then
        version="$(sed 's/^[^0-9\]*\([0-9.]\+\).*$/\1/' "$file")"
        break
    fi
done

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 --rm $name:$version /bin/bash -c 'echo success'

rm -rf "$target"

Creating a docker Base Image

2 Answers2