How to update running kernel without reboot? I know about Oracle ksplice but it's not free and it supports only distributions that I don't use. Are there alternatives to ksplice?
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3 Answers
The underlying technology is free and part of the mainline kernel; Oracle just provides prebuilt images. You can build your own ksplice patches to dynamically load into your own kernel.
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That's nice! But where is it in menuconfig or how is it called in .config? Feb 25, 2012 at 14:38
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Hey, I've posted a follow-up on Ask Ubuntu that you might be able to answer (or help on): askubuntu.com/questions/193069/…– OliSep 26, 2012 at 7:01
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1It might be nice to add more details to this answer instead of creating 2-sentence answers Oct 22, 2015 at 9:23
It is an old question, but it shows up on top of google, and a lot of things has changed since then. Here are ksplice alternatives as of now:
Livepatch is the technology in mainstream kernel. Canonical provides kernel livepatch service for Ubuntu 16.04 and later. It is free for up to 3 machines for personal use or up to 50 machines if you are a recognised Ubuntu Community member. If you are neither - you can use it for a fee in an Ubuntu Advantage support subscription ($225-$1,500/machine/year on physical servers, $75-$500/machine/year - on VMs), which is still cheaper than ksplice option. Unlike other solutions in the list, it allows administrators to create their own patches but it can be difficult and time-consuming work. Amazon Linux recently announced livepatch support (beta) for Amazon Linux 2 as well. No other distros offers live patching services (even though technology is integrated into the kernels) .
Kpatch is Red Hat’s own rebootless kernel live patching tool based on livepatch. It was announced in 2014. It works on RHEL and its derivative and is available as a part of the Premium support subscription ($1,299 per year).
SUSE’s Kgraft live patching solution only supports SUSE’s own Linux Enterprise Server 12. The prices start from $699/year per 2 sockets or $1,890/three years per 2 sockets. They have the longest trial period - 60 days, but there are some limitations from an architectural perspective.
KernelCare - automated live patching solution, covers most of the popular distributions, including CentOS, RHEL, Oracle Linux, Debian, Ubuntu, Amazon Linux and others. KernelCare also supports the Glibc and OpenSSL patching without a reboot. It also offers custom and fixed-date patching to meet the specific needs. A 30-day trial is available and subscription options start from $2.25/server/month for kernel patching only and $5.45/server/month for kernel and Glibc/OpenSSL package.
One alternative to ksplice is kexec(). Rather than patching the Linux kernel whilst running, this command essentially replaces the current kernel with a new one without rebooting your system.
In order for this to be available, it needs to be turned on as a compiler option in your distribution's kernel - that is, you can compile kernels without this functionality, so you'll need to check it is available and/or enable it yourself.
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5Replacing the current kernel with a new one effectively is rebooting, just without the bother of going through the boot loader. You still end up having to save your work, shutdown, and restart your applications.– psusiFeb 25, 2012 at 20:07
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(debian/ubuntu) kexec-tools appears to not be ported to support systemd at this time; and as far as I know neither current package repository is supporting any init besides systemd; so kexec is off the table in debian land currently; Jan 8, 2019 at 18:23
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@psusi I believe kexec avoids actually powering off the hardware, such that the mainboard does not need to spend time to POST, nor does any pci device need to initialize from scratch - a feature I highly sought after when the hardware takes multiple minutes to cold boot :cry: Jan 8, 2019 at 18:25