Xubuntu 10.10 Kernel Updates modifying Kernel Settings PenStick

metallica1973 · 11-18-2010, 11:02 AM

I have made a several modifications to my penstick running Xubuntu 10.10 that have greatly enhanced its performance. It took me several weeks to get to this point. I have added entries to /etc/rc.local and added kernel tweaks in /etc/grub.d/40_Custom so that my entries wont be erased. I have also added entries in my /etc/fstab. I have read this document in regards to the kernel but I am concerned about my /etc/fstab,/etc/rc.local and /etc/grub.d/40_Linux files being overwritten from updates.

https://help.ubuntu.com/community/Grub2

I am concerned about when one of my users decides he wants to run his updates via apt-get or package managers that all of the configs that I have done will be wiped away. Can someone enlighten me on this. Thanks

tommcd · 11-18-2010, 11:07 PM

Quote:

Originally Posted by metallica1973

I am concerned about when one of my users decides he wants to run his updates via apt-get or package managers that all of the configs that I have done will be wiped away.

If the users only run updates and install software, the entries in /etc/fstab, /etc/rc.local, and /etc/grub.d/40_custom will persist after any updates, including kernel updates.
Unless your users edit or change fstab, rc.local, or 40_custom, all of your configurations in those files will persist. By the way, there are also a lot of configure options for grub2 in /etc/default/grub that you may want to look at.
Also, the correct file name is /etc/grub.d/40_custom, not /etc/grub.d/40_Linux. If you changed the file name to 40_Linux it probably will still work ok though.
Hope this helps.

metallica1973 · 11-19-2010, 08:56 AM

sorry for the typo and many thanks. I will definitely look into /etc/default/grub. I feel better knowing this. One more questions:

If I create a custom entry using /etc/grub.d/40_Custom like this:

PHP Code:



#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry 'Ubuntu, with Linux 2.6.35-22-generic' --class ubuntu --class gnu-linux --class gnu --class os {
        recordfail
        insmod part_msdos
        insmod ext2
        set root='(hd1,msdos1)'
        search --no-floppy --fs-uuid --set d6d52b91-aa3c-491b-b760-479da6a957cf
        linux   /boot/vmlinuz-2.6.35-22-generic root=UUID=d6d52b91-aa3c-491b-b760-479da6a957cf ro   quiet splash elevator=noop
        initrd  /boot/initrd.img-2.6.35-22-generic
}

and a user runs his updates and a new kernel is downloaded and installed. I am pretty confident that this entry will not hold. Please tell me I am wrong. If this is the case how can I prevent the user from downloading and using a different kernel build on my penstick? thanks

widget · 11-19-2010, 01:10 PM

The only thing that would change the boot from that entry would be a change in its place in the menu order.

The easy way to prevent this is to change the permissions of /etc/grub.d/10_linux to not be executable. This is assuming you are booting from the grub on your usb device. If that is the case then 10_linux is what generates the menu entry.

Disable that and change the name of 40_custom to 06 custom, which will put it at the top of your menu and make sure /etc/default/grub is calling for;

Quote:

GRUB_DEFAULT=0

will make it impossible for the user to boot to anything but your entry.

If you just change the name to 06_custom, have the above in /etc/default/grub and leave 10_linux alone it will still be the default boot but any kernel updates will be listed right under it in the menu so that they can be used.

tommcd · 11-20-2010, 12:15 AM

Quote:

Originally Posted by metallica1973

If I create a custom entry using /etc/grub.d/40_Custom like this: ...

Just for reference, here is mu custom boot file in /etc/grub.d/ that I use for booting Slackware's generic-smp kernel. I named the file 31_Slackware32-13.1 so it would show up after the Ubuntu entries in the grub2 menu on bootup:

Code:

menuentry "Slackware32-13.1 on /dev/sda5" {
        set root=(hd0,5)
        linux  /boot/vmlinuz-generic-smp-2.6.33.4-smp root=/dev/sda5 ro 
        initrd  /boot/initrd.gz
}

Then I just made this file executable and ran "sudo update-grub" and it persists in the grub2 menu after any Ubuntu kernel updates.

metallica1973 · 11-24-2010, 08:58 AM

many thanks. After really thinking about, all I need is to just add what I need in /etc/rc.local and that will add the junk I need every time the system starts but If needed I will definitely modify what is needed to /etc/grub.d/. Awesome thanks