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oVirt Node NG RPM Persistence Deep Dive

Ryan Barry
January 24, 2017

oVirt Node NG RPM Persistence Deep Dive

oVirt Node is a composed hypervisor image which can be used to provision virtualization hosts for use with oVirt out of the box, with no additional package installation necessary.

oVirt Node is upgraded via yum in an A/B fashion, but the installation of a completely new image means that packages which have been installed on a previous version of the hypervisor were lost on upgrades, or required reinstallation.

With oVIrt 4.1, oVirt Node will cache and reinstall packages installed with yum or dnf onto the new image, ensuring that customizations made by users or administrators are kept.

The advantages of keeping packages across upgrades:
- ability to persistently modify oVirt Node with additions for tooling or support
- removes the need to build a brand-new image with a modified kickstart to modify oVirt Node
- simplified management

Session outline:
- Next-generation oVirt Node overview
- yum API overview
- oVIrt Node integration with yum/dnf to persist RPMs across upgrades

Ryan Barry

January 24, 2017
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  1. oVirt Node NG RPM Persistence, January 2017 oVirt Node NG

    RPM Persistence Deep Dive Ryan Barry <[email protected]> 17/10/2016
  2. oVirt Node NG RPM Persistence, January 2017 • • ◦

    Compatibility between the products on the old and new layers is verified ◦ /etc and /root migrated to the new layer ◦ UID/GID drift between images is corrected ◦ Permissions and ownership from RPM are fixed on the new layer ◦ The bootloader is updated ◦ A new initrd is generated ◦ (4.1) -- RPMs are persisted
  3. oVirt Node NG RPM Persistence, January 2017 • ◦ This

    is an acceptable risk, since configuration-management systems and administrators use yum in the majority of cases ◦ Something to be aware of if you still `rpm -Uvh foo.pkg`. • ◦ Reconstructing RPMs from the rpmdb on the system was investigated, but it’s almost impossible to do this reliably, to say nothing of package signing. ◦ oVirt Node NG 4.0 will still warn users and administrators that packages will not be persisted and this is correct. RPM persistence is unlikely to be backported.