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Howto create a Docker Image for RHEL
RHEL docker images are not available from Docker Hub. It’s available from Redhat docker registry and the catalog can be accessedhere. However there could be cases where you might want to create a RHEL docker image from scratch. The following steps will guide you to create a RHEL docker image from scratch. While these steps are for creating RHEL 7.1 LE docker image on PowerPC servers, the same can be applied for creating RHEL docker image on Intel servers as well.
The steps below have been performed on an Ubuntu 15.10 OS running as a PowerKVM guest. However you can run the same steps on RHEL or Fedora as well.
Pre-requisites
Access to RHEL package repository. You can use a local repository created from RHEL installation ISO as described below
# mkdir -p /mnt/rhel7-repo
# mount -o loop RHEL-LE-7.1-20150219.1-Server-ppc64le-dvd1.iso /mnt/rhel7-repo/
Install ‘yum’ package. This is not required on a RHEL or Fedora system as it’ll be there by default.
# apt-get install yum
Steps to create a RHEL docker image
Create a new RPM root directory
# mkdir /rhel7-root
# export rpm_root=/rhel7-root
Initialize the new RPM root directory# rpm --root ${rpm_root} --initdb
The rest of the install instructions will use this new RPM root as the install destination for a minimalistic RHEL OS.
Install the redhat-release-server rpm package for RHEL 7.1 LE
# rpm --root ${rpm_root} -ivh /mnt/rhel7-repo/Packages/redhat-release-server-7.1-1.ael7b.ppc64le.rpm
Configure yum repositories as required.
For example if you want to use only the local repository, then do the following
# rm -f ${rpm_root}/etc/yum.repos.d/*.repo
# cat >${rpm_root}/etc/yum.repos.d/rhel71le.repo<<EOF
[rhel71le]
baseurl=file:///mnt/rhel7-repo/Server
enabled=1
EOF
cat >${rpm_root}/etc/yum.repos.d/rhel71le.repo<<EOF
[rhel-debuginfo]
name=Red Hat Enterprise Linux $releasever - $basearch - Debug
baseurl=file:///mnt/rhel7-repo/Server
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
EOF
rpmdb: /var/lib/rpm/Name: unexpected file type or format
Indeed, it’s a corrupt rpm database. Steps to resolve:
- Check for processes holding the rpm database open (usually in MUTEX/FUTEX states):
lsof | grep /var/lib/rpm
If it finds any, kill -9 them all.
- Delete any temporary DB files:
rm -fv /var/lib/rpm/__*
- Rebuild your RPM database:
rpm --rebuilddb -v -v
If you still have problems, a reboot is probably quickest, then repeat steps 2 and 3 above.
yum install setuptool tar vi unzip
If you encounter ‘No such file or directory’ error, then you’ll need to create the /etc/yum.repos.d directory.
Import GPG keys
rpm --root ${rpm_root} --import /mnt/rhel7-repo/RPM-GPG-KEY-redhat-*
Install minimalistic RHEL OS
# yum -y --installroot=${rpm_root} install yum
This will install a minimalistic RHEL OS under /rhel7-root
Additional Customization
Chroot to the new RHEL installation and perform any additional customizations if required
# chroot ${rpm_root} /bin/bash
bash-4.2# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.1 (Maipo)
Convert this RHEL installation to a docker image
# tar -C ${rpm_root}/ -c . | docker import - rhel7le
9a6dac402e2bf561f833f644337f3061c6ff70ec906472d5c008755ca9ed7f1d
# docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
rhel7le latest 9a6dac402e2b 11 seconds ago 360.6 MB
Use the new RHEL docker image
# docker run --hostname='rhel7-container' rhel7le uname -a
Linux rhel7-container 4.2.0-10-generic #12-Ubuntu SMP Tue Sep 15 19:46:04 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux
Once you have created the RHEL docker image, you can push it to your local registry for sharing. Hope this will be of some help to you in your docker journey.
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