How do I update kernel safely?

[sunmacet]

We are having kernel panic about once a day. We would like to update kernel first before we look more options to find out what is the problem.

Command "yum update kernel" gives newer kernel but is kernel update safe? This is production server and major downtime is not an option. Also we don't have access to console, so if boot fails we need to call to our server provider that might take too long time.

Is there any means to be safe with kernel update? Is there ways to setup GRUP so that it will use older kernel if the newer fails? Any other means to make the kernel update more safe? In generally is these yum kernel updates safe? Any other thought?

Thank you for your time.

 

[atomicturtle]

Yup with the panic flag, take a look at this: http://www.atomicorp.com/wiki/index.php/Kernel_Panic , steps 4 and 5.

 

[sunmacet]

Thank you. It seems to be exactly what I was looking for. I will make the kernel update when I get the courage.

I have some very bad memories about kernel update from about 7 years ago that still haunts me.

 

[atomicturtle]

that should do it then. If the kernel doesnt boot for some reason, which is what that page is all about, it will automatically reboot into whatever other kernel you defined as default.

 

[Amin Taheri]

also you should try to use yum install kernel instead of yum update as the update will remove the previous version but install will keep them all.

 

[atomicturtle]

oh man good point. Never use rpm -U with a kernel, always use rpm -i. Thats what yum install does too, the difference is that -U is an upgrade of the existing package, and -i (with kernels ONLY) will install an addition kernel, rather than replace the existing one.

 

[sunmacet]

oh, i did use yum update...

however it seems that /boot has the old vmlinuz and initrd, does it mean that I am safe? haven't rebooted yet...

 

[breun]

AFAIK yum update doesn't remove all your old kernels (see installonlypkgs in /etc/yum.conf). rpm -U does.

however it seems that /boot has the old vmlinuz and initrd, does it mean that I am safe? haven't rebooted yet...

See what's in /etc/grub.conf.