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script to update kernel parameter in grub.conf

Posted on 2011-03-17
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Last Modified: 2012-06-21
Hi

Could you please help me to create a shell script to update kernel parameter in grub.conf. As per the VMware KB

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006427

I need to add the kernel parameter. I need to do this for RHEL4 64bit systems. I have below given kernels to modify.

2.6.9-89.0.23 with this I need to add notsc
2.6.18-128 with this I need to add notsc divider=10
2.6.9-55 with this I need to add notsc

Any help will be appreciated.

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Question by:upanwar
4 Comments
 
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Assisted Solution

by:Alberto Cortes
Alberto Cortes earned 668 total points
ID: 35158270
I recommend you to edit /boot/grub/grub.conf and add the parameters as follows:
1. cp /boot/grub/grub.conf /boot/grub/grub.conf.old
2. vi /boot/grub/grub.conf
3. Add parameters to the end of the line, for example:
Original line is:
    kernel /vmlinuz-2.6.18 ro root=/dev/hda2
and you want to add "notsc divider=10", the updated text is:
    kernel /vmlinuz-2.6.18 ro root=/dev/hda2 notsc divider=10
4. Save and test by rebooting.
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Accepted Solution

by:
pilson66 earned 664 total points
ID: 35164490
For quick editing, you can use a utility "sed"
Example:
 
sed -i 's/kernel \/vmlinuz-2.6.18 ro root=\/dev\/hda2$/kernel \/vmlinuz-2.6.18 ro root=\/dev\/hda2 notsc divider=10/g' /boot/grub/grub.conf

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But in this case, no backup is created.
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LVL 31

Assisted Solution

by:farzanj
farzanj earned 668 total points
ID: 35169697
You can do this:
sed -i -e "s/kernel.*/& notsc/" -e "s/.*2.6.9-55.*/& divider=10/" /boot/grub/grub.conf

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Having said that, why are you doing this.  Scripts are written to tasks that are recurring.  Seems like you have to modify it just once.

Furthermore, I think what you are really looking for is: having kernel parameters appropriate to whatever kernel you select.

To accomplish that, what you should do is this:

Add a little script in your /etc/rc.d/rc.local.

Find the name of the kernel with uname and do write the /proc/ values of these parameters

Something like
[[ $(uname -a) =~ '2.6.9-89.0.23' ]] && /proc/path/file > value

I don't even have a RHEL 4 system anymore, but this is what I would think
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LVL 12

Author Closing Comment

by:upanwar
ID: 35181005
I have managed to write it with the help of grubby. Which is great. But anyways everybody have put their efforts so thanks all of you.
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