Rollback Procedure for Kernel Patching
We can also boot from old kernel, if any problem occurs with latest updated kernel. We can achieve this in 2 ways
- Booting Time: While booting, we can select the kernel type that you want boot from. Once you select, it will boot through selected kernel. However, if you want change perminently, you need to change configurational file i.e /etc/grub.conf file.
- Configuration file change: To make permanent changes for kernel, we have only one way i.e.changing configuration file. Here, 1st kernel is 2.6.18-348.e15, and 2nd kernel is 2.6.18-164.e15.The default value is “0” that means server always boot with 1st kernel only. If you want to change perminently, just you require to change “0” to “1” then next boot onward it will boot from 2nd kernel.
# cat /etc/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/hda2
# initrd /initrd-version.img
#boot=/dev/hda
default=1 –>0 to 1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-348.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-348.el5 ro root=LABEL=/ rhgb quiet
initrd /initrd-2.6.18-348.el5.img
title Red Hat Enterprise Linux Server (2.6.18-164.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5 ro root=LABEL=/ rhgb quiet
initrd /initrd-2.6.18-164.el5.img
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