Ksplice: Kernal Update Without Reboot

[Ksplice image courtesy Linux by Knight]
Ksplice: Kernel Update Without Reboot

Abstract:
Operating Systems normally comprise two distinct layers: the kernel and the user space. Normally, updating the kernel would require a reboot, so the OS can apply a new kernel module. Operating Systems like Solaris created a mechanism called "live update" to update OS Kernel, OS User Space, or even third-party applications (not to mention provide rollback) with merely a reboot. Oracle Solaris 11 facilitates virtually unlimited patch/rollback cycles leveraging ZFS. The new Ksplice tool from Oracle allows for Linux to get closer to Solaris uptime requirements by providing for kernel updates without reboot, leaving OS User Space and Applications to normal reboot or application restart cycles.

Overview:
Ksplice is a feature of Oracle Linux which installs kernel updates on live systems without reboot, it is free with Oracle Premier Linux Support, and is available today. Even IBM an developer network has some nice things to say about Ksplice, owned by Oracle, and provides a detailed description of how it works.

Caveats:
Ksplice will only work on kernel code distributed by Oracle, no third-party open source kernel modules. Ksplice: facilitates kernel updates in the memory of the system; is used in conjunction to Yum or Uptodate for Kernel and OS User Space binaries on-disk; does not provide for a mechanism to update applications.

Example Commands:
Some important commands, highlighted in a recent screen cast from Oracle include:
uptrack-update - allows for kernel version updates on a live system without boot
uptrack-uname - shows updates on the
uptrack-show - shows updates and effective kernel version
uptrack-remove - allows rollback of kernel versions on a live system without boot
/etc/init.d/uptrack - installs Ksplice kernel updates or on-disk kernel on [re]boot; allow on-disk kernel or even allows to automatically install updates dynamically.
http://uptrack.ksplice.com/ - Web GUI interface to see updates on all servers


Screen Cast Video:
This screen cast provides a Ksplice overview, kernel patching demo, as well as a FAQ.


Network Management Implications:
Solaris offers a single reboot for OS Kernel, OS User Space, and Applications updates, while Ksplice provides Oracle Enterprise Linux with a way to increase availability to avoid reboots with OS Kernel updates (while leaving third-party drivers, OS User Space, and Applications with solving the problem by themselves.)

With the ability of modern operating systems like Oracle Solaris and Oracle Linux to provide near 100% availability (with security), network management systems will increasingly leverage these two foundational components, so managed services providers will be able to provide better availability to their customers than ever before.

Solaris 11 Preview (Part 2)

Solaris 11 Preview (Part 2)

Timothy Prickett Morgan from The Register wrote an excellent article "Oracle previews Solaris 11, due in November" which spurred some contemplations.

Solaris 11 Performance Features


In the "Pushing Solaris to 11" section, TPM talks about the features added to Solaris 11.

One of the things that probably took some extra time was doing optimizations in Solaris specifically for Oracle software, which Fowler touched on here

I honestly don't think that these features pushed out Solaris 11 release. Many of them appeared in Solaris 10 Update 10, so I don't think the Solaris 11 "extra time" was necessarily due to many of these features.

Solaris 10 Update 10 Performance Features

Some of the features mentioned in the "New in Oracle Solaris 11" happened to make it into Solaris 10 Update 10 - which many in the market are very pleased about.

In particular, some of the items included: ISM, DISM, RDSv3, many improvements in various threading libraries.

Other features, not mentioned in the release notes, but mentioned in Solaris 10 Update 10 patch notes include: T4 support, low latency socket framework


[time slider illustration]
Solaris 11 Upgrade Features

TPM also mentioned Fowler speaking about upgrade ease.

Solaris 11 will, for instance, have one button rollback features so if customers don't like the results of their upgrade to Solaris 11

With Solaris 11's integration with ZFS, multiple boot environments consume virtually no disk space, and upgrades can be done where the old boot environments may be allowed to remain in place (indefinitely, without losing OS mirroring capability), as with old Live Upgrade requirements. It just takes a keystroke to select the old boot environment under Solaris 10 Update 10 or Solaris 11.

There is an additional "time slider", which is part of OpenSolaris, Solaris 11 Express, Solaris 11, and various other Solaris derivative operating systems - being able to turn back time on a system is pretty wonderful. Fowler may have been alluding to this.

Solaris 10 Update 10 Upgrade Features

One of the features mentioned in the Solaris 10 Update 10 was the Live Upgrade of Solaris 10 using ZFS. I classified this as a "performance" enhancement, since Live Upgrade existed under Solaris 10 with easy rollback in the past, but it required a mirrored disk.

The Live Upgrade enhancement using ZFS is now here, for Solaris 11. The time-slider, from Solaris 11 is not.