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Scenario:

Ubuntu 13.04 is already installed with seperate promary partitions for -

  • UEFI Boot area
  • /boot
  • /home
  • /
  • swap

Attempt to reinstall ubuntu 13.04 and in the partitioning options, select 'something else'

Problems:

  1. Although the existing partitions are shown, none have the filesystem format and mount point fields populated in the table.
  2. I sometimes am given the option of UEFI boot area partition, and sometimes I am not - leaving me with just the BIOS boot area partition option.
  3. Which partition/device to select to install grub on at the bottom drop down option?
  4. Which partition to select if I want to re-install ubuntu without affecting the /boot and /home partitions
  5. Selecting any partition and trying to re-install always show a different partition size as available.
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2 Answers 2

I'm not sure about all of your problems, but I can say this:

  1. I'm not sure about the filesystem-identification problem. I don't have every aspect of the Ubuntu installer memorized, so I'd need to experiment to figure out whether what you describe is normal; and if not, what the problem might be.
  2. This sounds like sometimes you're booting the installer in EFI mode and sometimes in BIOS mode. Your original installation was almost certainly done in EFI mode, so I recommend sticking with that. You can check the boot mode by dropping to a shell and looking for a directory called /sys/firmware/efi; if it's present, you've booted in EFI mode, and if not you've probably booted in BIOS mode. If the installer tries to set up an EFI System Partition (ESP; what the Ubuntu installer confusingly calls an "EFI boot partition," IIRC) then you've probably booted in EFI mode. If the installer wants to set up a BIOS Boot Partition, then you've probably booted in BIOS mode. You can usually control the boot mode via a firmware boot manager, but how to get into it and what options it shows vary greatly from one computer to another. Usually you activate it by pressing a function key early in the boot process (before any Linux boot manager appears).
  3. In EFI mode, there should probably be no option about where to install GRUB, although this is one of the aspects of the installer that I haven't memorized. If there is an option for this in EFI mode, then it's either bad user interface design or it should ask about which of several ESPs to use, and your answer in either case probably doesn't matter. In BIOS mode, the MBR is probably the best choice, although as I say, I think you should be installing in EFI mode.
  4. To install over an existing system, you need to identify your old root (/) partition as your new root partition, and tell the installer to erase the partition's existing contents. I don't recall the exact user interface details to do this. It will be a little bit easier to set up if you also tell it to mount the old /home partition at /home, but you must be very careful to tell it to not erase the contents (the installer might use the term "format" or "reformat" rather than "erase"). If you're replacing the existing system, you probably do want to erase /boot, if it's a separate partition, although failing to do so won't be fatal -- you might just end up with some non-functional items in your boot menu.
  5. I'm not sure what you're saying here. If you're saying that the program is giving inconsistent data on the size of a single partition, then this could be a sign of a serious bug or hardware fault -- or it could be user error. (You might be intending to select one partition but instead select different ones by accident, for instance.)

Be sure to back up your user data before a re-installation. Although this process usually goes smoothly if you're careful, it can go badly if you make a mistake, or occasionally if there's a bug in the installer.

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For point#5, I read somewhere that the standards Ubuntu installer uses make rounding to cylinder and 1MB=1000KB instead of 1024 and the same for GB and TB, which could create issues with partitioning. –  charlie May 11 '13 at 20:54
    
Cylinder alignment is largely a thing of the past, so unless you're using an old distribution, that shouldn't be an issue. The differences between kilobytes (kB; 1000 bytes) and kibibytes (KiB; 1024 bytes) and larger multiples of these can certainly cause confusion, since Utility A may use one measure and Utility B may use another. Sometimes power-of-2 units (KiB, MiB, etc.) are incorrectly reported using power-of-10 suffixes (kB, MB, etc.). There can also be different values depending on whether total or available space is being reported. –  Rod Smith May 11 '13 at 23:48

If u want to format the /root partition, boot from live CD and open gPartition editor and format the relevant drive. then try to install. I think it may help u.

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