TOPIC: BIOS
Restoring GRUB for dual booting of Linux and Windows
11th April 2015
Once you end up with Windows overwriting your master boot record (MBR), you have lost the ability to use GRUB. Therefore, it would be handy to get it back if you want to start up Linux again. Though the loss of GRUB from the MBR was a deliberate act of mine, I knew that I'd have to restore GRUB to get Linux working again. So, I have been addressing the situation with a Live DVD for the likes of Ubuntu or Linux Mint. Once one of those had loaded its copy of the distribution, issuing the following command in a terminal session gets things back again:
sudo grub-install --root-directory=/media/0d104aff-ec8c-44c8-b811-92b993823444 /dev/sda
When there were error messages, I tried this one to see if I could get additional information:
sudo grub-install --root-directory=/media/0d104aff-ec8c-44c8-b811-92b993823444 /dev/sda --recheck
Also, it is possible to mount a partition on the boot drive and use that in the command to restore GRUB. Here is the required combination:
sudo mount /dev/sda1 /mnt
sudo grub-install --root-directory=/mnt /dev/sda
Either of these will get GRUB working without a hitch, and they are far more snappy than downloading Boot-Repair and using that; I was doing that for a while until a feature on triple booting appeared in an issue of Linux User & Developer that reminded me of the more readily available option. Once, there was a need to manually add an entry for Windows 7 to the GRUB menu too and, with that instated, I was able to dual-boot Ubuntu and Windows using GRUB to select which one was to start for me. Since then, I have been able to dual boot Linux Mint and Windows 8.1, with GRUB finding the latter all by itself. Since your experiences too may show this variation, it's worth bearing in mind.
Restoring the MBR for Windows 7
25th November 2010
During my explorations of dual-booting of Windows 7 and Ubuntu 10.10, I ended up restoring the master boot record (MBR) so that Windows 7 could load again or to find out if it wouldn't start for me. The first hint that came to me when I went searching was the bootsect command, but this only updates the master boot code on the partition, so it did nothing for me. What got things going again was the bootrec command.
To use either of these, I needed to boot from a Windows 7 installation DVD. With my Toshiba Equium laptop, I needed to hold down the F12 key until I was presented with a menu that allowed me to choose from what drive I wanted to boot the machine, the DVD drive in this case. Then, the disk started and gave me a screen where I selected my location and moved to the next one where I selected the Repair option. After that, I got a screen where my Windows 7 installation was located. Once that was selected, I moved on to another screen from I started a command line session. Then, I could issue the commands that I needed.
bootsect /nt60 C:
This would repair the boot sector on the C: drive in a way that is compatible with BOOTMGR. Though this wasn't enough for me, it was something worth trying anyway in case there was some corruption.
bootrec /fixmbr
bootrec /fixboot
The first of these restores the MBR, and the second sorts out the boot sector on the system drive (where the Windows directory resides on your system). In the event, I ran both of these and Windows restarted again, proving that it had come through disk partition changes without a glitch, though CHKDISK did run in the process, but that's understandable. There's another option for those wanting to get back their boot menu, and here it is:
bootrec /rebuildbcd
Though I didn't need to do so, I ran that too, but later used EasyBCD to remove the boot menu from the start-up process because it was surplus to my requirements. That's a graphical tool that has gained something of a reputation since Microsoft dispensed with the boot.ini file that came with Windows XP for later versions of the operating system.
Booting from external drives
16th September 2009
Sticking with older hardware may mean that you miss out on the possibilities offered by later kit, and being able to boot from external optical and hard disk drives was something of which I learned only recently. Like many things, a compatible motherboard and my enforced summer upgrade means that I have one with the requisite capabilities.
There is usually an external DVD drive attached to my main PC, so that allowed the prospect of a test. A bit of poking around in the BIOS settings for the Foxconn motherboard was sufficient to get it looking at the external drive at boot time. Popping in a CrunchBang Linux live DVD was all that was needed to prove that booting from a USB drive was a goer. That CrunchBang is a minimalist variant of Ubuntu helped for acceptable speed at system startup and afterwards.
Having lived off them while in home PC limbo, the temptation to test out the idea of installing an operating system on an external HD and booting from that is definitely there, though I think that I'll be keeping mine as backup drives for now. Still, there's nothing to stop me installing an operating system onto of them and giving that a whirl sometime. Of course, speed constraints mean that any use of such an arrangement would be occasional but, in the event of an emergency, such a setup could have its uses and tide you over for longer than a Live CD or DVD. Having the chance to poke around with an alternative operating system as it might exist on a real PC has its appeal too, and avoids the need for any partitioning and other chores that dual booting would require. After all, there's only so much testing that can be done in a virtual machine.