Is it possible to rollback an applied Kernel Update on a RHEL5 server?

MusicIT

Recently one of the system administrators did a yum update of the servers which applied the newest kernel for the system, but the new kernel is not working well with what the servers are designed to do. Is there a way that you can roll back the changes made to the previous version? Thank You for any help.

paul78

Most distros that I am familiar will keep the old kernel and modules. You should be able to still boot to the old kernel. Check the boot partition and see if the previous kernel is still there and add it as a boot option to your bootloader if it isn't already there. I normally do kernel updates manually to avoid compatibility issues so I am less familiar with how rhel does it.

jibbajabba

You can, unless you removed the old kernel.

At the beginning of the boot, it offers you to press a key for more options. If you do that it will show all installed kernel - just select the one you want and you are ready to go.

To change it so it boots automatically, edit the /etc/grub.conf

#boot=/dev/sda
default=0
timeout=15
#splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console

title Red Hat Enterprise Linux Server (2.6.17-1.2519.4.21.el5xen)
	root (hd0,0)
	kernel /xen.gz-2.6.17-1.2519.4.21.el5 com1=115200,8n1 dom0_mem=256MB
	module /vmlinuz-2.6.17-1.2519.4.21.el5xen ro
	root=/dev/VolGroup00/LogVol00
	module /initrd-2.6.17-1.2519.4.21.el5xen.img

title Red Hat Enterprise Linux Server (2.5.12-1.2519.4.24.el5xen)

Here you can see the server got two ... the top of the file says "default=0" - change it to the one you want, or simply comment the most recent out.

jmritenour

So there's two methods of applying a new kernel. Install and upgrade. Install adds the new kernel image to your /boot directory, and sets your grub/lilo config to point that as the default. The old kernels will still be tact, and available via grub.

Upgrade overwrites all previous kernels.

If he just ran "yum update", then the old ones will be in tact. "yum upgrade kernel" however, would over write the old ones. That said, it is possible to get a RPM for a previous kernel & install it manually.