Examples of grub usage (as a reminder mostly)
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Contents: [Dobrica Pavlinušić's random unstructured stuff]
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Sometimes, grub-install won't owerwrite MBR. If that happends, first reinstall MBR and then grub:
install-mbr /dev/sda grub-install /dev/sda
If you forget to make /boot/grub/menu.lst (as I did), you will have to do a lot of typing in grub console, so be sure to also run
update-grub
There is also corner-case when you have lvm compiled into kernel and /boot partition on LVM. grub will be confused, and simplest solution that I found so far is to move /boot to partition. If you don't have any free space handy, you might try to move swap to LVM and /boot onto swap partition.
After you have installed grub, you might want to configure fallback kernels. First configure different kernels, with fail-safe one as last one:
/boot/grub/menu.lst
default saved fallback 1 2 title OpenVZ 2.6.18-028test010 root (hd0,2) kernel /vmlinuz-2.6.18-028test018 root=/dev/mapper/vg-root ro initrd /initrd.img-2.6.18-028test018 savedefault fallback boot title Debian GNU/Linux, kernel 2.6.18-028test007.2-ovz-enterprise root (hd0,2) kernel /vmlinuz-2.6.18-028test007.2-ovz-enterprise root=/dev/mapper/vg-root ro initrd /initrd.img-2.6.18-028test007.2-ovz-enterprise savedefault fallback boot title Debian GNU/Linux, kernel 2.6.18-3-686 root (hd0,2) kernel /vmlinuz-2.6.18-3-686 root=/dev/mapper/vg-root ro initrd /initrd.img-2.6.18-3-686 savedefault boot
Here is simplier alternative:
default 0 fallback 1 title Debian GNU/Linux root (hd0,0) kernel /boot/vmlinuz root=/dev/md0 reboot=warm title Debian GNU/Linux, with the old kernel root (hd0,0) kernel /boot/vmlinuz.old root=/dev/md0 reboot=warm
Then setup reset to default kernel (0) upon successful boot. On debian, you can just add following line in /etc/rc.local:
grub-set-default 0
You might also want to run this once by hand, so that first boot is in first kernel (most recent one presumably).