[SOLVED] Linux kernel update

[ple]

Hi,
How often do you, Zimbra system admin, upgrade the Linux kernel? Linux releases kernel updates all the time; do you apply the updates every time or you just simply use "if it isn't broke; don't fix it"? My only concern is how well Zimbra take on the kernel changes. Any thoughts?
Thanks.
PL
RHAS5
ZCS5.0.16

[sylvester_0]

It's recommended that you apply all updates/kernel updates that are available through your distributions update channel (APT, YUM, etc). Doing so will ensure you're keeping up with any vulnerabilities or bugs that are found. In my years of using desktop/server linux I've never seen a kernel update affect application performance/stability. It is not necessary to compile the newest available kernels from kernel.org.

[ple]

Thanks for quick response. The reason I'm asking is because I did have a bad experience with one third-party application that broke right after I update the kernel. Sounds like it is not the case with Zimbra.
PL

[bradb21]

Sometimes the application will have drivers that need to be recompiled after a kernel upgrade, but other than that I've never had an issue. I usually will take the downtime and upgrade, but lately I haven't had the time. My server has been up for about 8 months now, and I probably won't bring it down for upgrades until Zimbra 6.0 is final and I do my Zimbra upgrade. I'll upgrade the kernel at that time.

[uxbod]

Well, one should ask why you do not have a dev/test environment to prove the upgrade first ? I do appreciate though that with this approach there is a cost implication. If a kernel update does go wrong then you can always switch back to the previous kernel by updating grub.lst (or any other BL variant). As others have said it is always best to keep up with kernel, or any other security, updates but you have to balance risk aswell.

[sylvester_0]

Sometimes the application will have drivers that need to be recompiled after a kernel upgrade...

Yes, I've run across that with VMWare. But in that case it's because it needs to integrate with the host kernel to implement its network and other low level functions. If you're running a desktop linux you'll also notice that you need to recompile driver modules if you're using proprietary drivers. Nvidia drivers are an example of this but it's actually done automatically for you now.

The applications that make up the Zimbra stack (mysql, postfix, tomcat etc) don't and will never tie directly into the kernel in such a fashion so IMHO you shouldn't ever have to worry about breaking Zimbra with a kernel upgrade.

Also, really the only time it's necessary to reboot a linux server is when you upgrade the kernel, though that should be changing soon enough! (see KSplice) Even when you upgrade to Zimbra 6.0 there should be no need to reboot the server - this isn't Windows.