Upgrading RHEL4.7 kernel but what to keep the old kernel in boot.grub

fcfury · 08-14-2009, 07:36 AM

Curious question I am upgrading the kernel on RHEL4.7 but for testing I am curious to see if I can upgrade the kernel but keep the old kernel for backup purposes. Like when the choice comes up at boot I can pick the old kernel if the upgrade of the new kernel messes up my system. I

MensaWater · 08-14-2009, 07:46 AM

That is the default way RHEL updates kernels.

If you're using up2date (RHEL3/RHEL4) or yum (RHEL5) to do the update then it will update grub.conf for you - it will make the new kernel the default but you can interrupt on boot up and select the older kernel.

Example grub.conf from one of my RHEL5 systems:

Code:

# 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 (hd0,2)
#          kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,2)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-128.2.1.el5)
        root (hd0,2)
        kernel /vmlinuz-2.6.18-128.2.1.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet crashkernel=128M@16M
        initrd /initrd-2.6.18-128.2.1.el5.img
title Red Hat Enterprise Linux Server (2.6.18-92.1.22.el5)
        root (hd0,2)
        kernel /vmlinuz-2.6.18-92.1.22.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet crashkernel=128M@16M
        initrd /initrd-2.6.18-92.1.22.el5.img

This has my current kernel (2.6.18-128.2.1.el5) and the kernel it replaced (2.6.18-92.1.22.el5).

fcfury · 08-14-2009, 08:13 AM

Cool, thanks so much thought that you actually had to edit the grub.conf file.

Quote:

Originally Posted by jlightner

That is the default way RHEL updates kernels.

If you're using up2date (RHEL3/RHEL4) or yum (RHEL5) to do the update then it will update grub.conf for you - it will make the new kernel the default but you can interrupt on boot up and select the older kernel.

Example grub.conf from one of my RHEL5 systems:

Code:

# 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 (hd0,2)
#          kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,2)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-128.2.1.el5)
        root (hd0,2)
        kernel /vmlinuz-2.6.18-128.2.1.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet crashkernel=128M@16M
        initrd /initrd-2.6.18-128.2.1.el5.img
title Red Hat Enterprise Linux Server (2.6.18-92.1.22.el5)
        root (hd0,2)
        kernel /vmlinuz-2.6.18-92.1.22.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet crashkernel=128M@16M
        initrd /initrd-2.6.18-92.1.22.el5.img

This has my current kernel (2.6.18-128.2.1.el5) and the kernel it replaced (2.6.18-92.1.22.el5).