Leveler

The idea of applying kernel patches on the fly and not needing to boot a new kernel is basically great. Whereas the overhead for a few systems is manageable, the coordinated reboot of hundreds or thousands of nodes in large deployments is a tour de force. The ability to apply remedies on the fly without much ado is a good thing, but it can take a while for the technology to reach the end user. Currently, it is still completely unclear where the journey is heading.

Advantage Red Hat

The Red Hat solution has some identifiable advantages over the SUSE idea. The fact that you do not have to patch the kernel to support live patches is certainly helpful. Also, the ability to field errors currently seems to work better in Kpatch than in kGraft.

Viewed superficially, both solutions seem to do the same thing, if you do not dig deeper into the topic. The differences only become apparent in use or during installation, which is so much easier with Kpatch than with kGraft – not to mention Kpatch's superior documentation.

The question always arises in kernel-related features as to where the solutions are headed. Both SUSE and Red Hat have announced that they want to see their live patch solution become part of the official kernel in the foreseeable future. For this to work, however, they must have the approval of Linus Torvalds, who has repeatedly made a name for himself in the past as a kernel Cerberus.

Torvalds also is known for not being amused about having multiple implementations in Linux for the same or similar features. Torvalds likely will not wave both kGraft and Kpatch past. Conceivably, one of the two solutions will prevail and the other will be ousted, or Torvalds will push for a joint venture, thus spawning a third solution combining the advantages of both systems.

If you want to try out Kpatch or kGraft today, you will not find matching packages listed in the openSUSE community version or in Fedora, which means a massive amount of manual work at the moment – for SUSE significantly more so than for Fedora.

The Author

Martin Gerhard Loschwitz is Principal Consultant at hastexo, where he is intensively involved with high-availability solutions. In his spare time, he maintains the Linux cluster stack for Debian GNU/Linux.