boot-repair appears to be a really excellent application. However, I just had a very scary experience with this application and want to report my experience and hopefully inspire the creators to change the way it works a bit, and also get people to perform a sanity check on my experience.
First, here was my situation. I had a 1TB seagate SATA drive that contained only ubuntu linux 10.4 LTS and no other operating systems. The partitions were:
I'm about 99.9% certain / and /backup were ext3 partitions, because I created this hard disk drive within a few days of ubuntu 10.40 being released, and I don't even recall ext4 being available then.
Somehow my MBR got smashed a couple days ago. I ended up ordering a whole new set of parts to fix and upgrade my computer, though it turned out that wasn't necessary. In case it matters, the new parts are: gigabyte 990FXA-UD7 motherboard, AMD 3.6GHz 8150 FX 8-core CPU, mushkin 2133MHz 8GB DDR3 RAM, 3TB @ 7200RPM seagate hard drive. The rest of the components were not changed (power-supply, DVD burner, nvidia GTX285 graphics card, etc).
I fiddled the BIOS to boot off the DVD, then booted the ubuntu installation DVD and performed the normal installation process to get ubuntu 10.4 LTS installed on the new 3TB hard disk drive. When that was finished, I powered it down, removed the ubuntu DVD, and it booted up just fine.
Then I disconnected the SATA3 cable to the 3TB drive and connected it to the old 1TB drive that stopped booting a couple days earlier. The system would then not boot up, just like before I rebuilt it.
Then I reset the computer and booted up into ubuntu on the DVD (the "live" or "try-it-out" version, or whatever it's called). Then I selected "Places -> Computer" and looked to see whether I could see the 1TB disk drive that would not boot. I could indeed, and the directory tree looked just fine. It appeared like nothing was missing. This led me to believe the MBR was busted, and/or the grub loader.
Then I put the ubuntu installation DVD in the DVD drive and tried again. It came up in with the usual screen that asked whether to boot ubuntu off the DVD, perform a memory test, or boot off the 1TB hard disk drive. When I told it to boot off the defective 1TB hard disk drive, it booted up just fine. This virtually proved my theory that only the MBR and/or grub loader was busted.
I spent a couple days searching for ways to fix my MRB. I found lots of talk about "grub-install" and various schemes with "dd", but I was never able to find out for 100% certain that no more than the first 446 bytes would be written with those techniques, and it was clear that the entire partition table would be destroyed if more than 446 bytes were written.
So I kept searching and eventually found the boot-repair application. So I downloaded it and ran it to take a peek at the drives and see what I could see.
I guess stupidly (as it turned out), I activated the "advanced features" checkbox, then looked around the GUI for what the application would do. In the end, I checked the options to create the "bootinfo summary" report, but UN-checked both "reinstall GRUB" and "restore MBR".
Then I clicked the "apply" button.
Later, when I ran gparted, I noticed with terror that my / and /backup partitions were now labeled as being ext4, not ext3 !!! What the frack, I thought. It wasn't supposed to change anything! Oh, freaking no!!! What have I done?
Anyway, I shutdown, removed the ubuntu installation DVD, then started the computer. To my amazement and relief, the freaking computer booted up ubuntu and everything seems to work.
Somehow, the MBR got fixed... even though both "reinstall GRUB" and "restore MBR" were NOT selected. Also, the "GRUB location", "GRUB options" and "MBR options" tabs were greyed out, further implying they were irrelevant. I wrote down the URL where the "bootinfo summary" was uploaded, and it is indeed there: http://paste.ubuntu.com/797990 . I also note that it did not display a "nothing was changed" dialog like is displayed when I simply cancel out of the "boot-repair" application without doing anything.
Maybe or probably I should have selected the button that creates the "bootinfo summary" on the main dialog window [non-advanced features]. However, later I tried that and it too doesn't display a "nothing was changed" dialog after the application ends... so I don't know what to think. That second bootinfo log is http://paste.ubuntu.com/798027 in case it matters. However, when I start the "boot-repair" application, do nothing and just quit out, it does display that "nothing was changed" dialog. Hmmmm.
So, my two issues and questions are:
#1: Why did it repair my the MBR [and/or GRUB] on my disk drive when I had both those options unchecked?
#2: Why did the two ext3 partitions on the hard drive all of a sudden become ext4 partitions after running boot-repair? Remember, that's what gparted says too, not just the "bootinfo summary". I suppose there is some tiny chance that I had ext4 partitions all along, but I really don't think so. Like I said, I don't think ext4 existed (in non-beta) when I created that disk drive in April 2010.
Anyway, it looks like boot-repair did exactly what I needed, and it is a very cool application. However, I think this behavior I observed needs to be fixed! It shouldn't modify the MBR and/or GRUB unless the related check-boxes are selected. And if it is changing ext3 to ext4... what's that all about?