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We've got an Asus X501A laptop (dec 2012) which has this UEFI thing. If I boot from an USB it only offers me to wipe the entire hard disc and install the new distro, or manual partitioning which I can't get my head around due to this UEFI thing. -- Note that this question has nothing to do with that other operating system named after openings in walls. Not interested in that.

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Ubuntu 13.04 64-bits detected right my Debian jessie. I didn't see any problem with it. –  Braiam Sep 22 '13 at 1:23

2 Answers 2

Likely because there are too many partition on the HDD. The installer does offer the "alongside" option, for example, if there are only two primary partitions. I suspect you may have three or four, in which case, the installer offers either wiping everything, or manual partitioning.

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If booting with UEFI and not BIOS/CSM/Legacy it has to be gpt partitioned which does not have primary partitions per se or no four primary partition limit like MBR(msdos). See post by Rod Smith. –  oldfred Sep 22 '13 at 3:54

If what mikewhatever says it true (namely, that Ubiquity removes "install alongside" if there are more than two partitions on a GPT disk), then that's a bug in the case of EFI/GPT systems. I didn't find any bug reports, but I might have entered the wrong search term. Perhaps somebody should file a bug report.

I can say that GPT partitioning isn't any harder for the user than is MBR partitioning. To the contrary, the lack of distinction between primary, extended, and logical partitions simplifies things greatly. (Technically, there's no such thing as a "primary partition" in GPT; there are just "partitions," with no qualifier. There can be up to 128 of them by default, although that value can be raised if necessary. Some partitioning tools insist on calling GPT partitions "primary partitions" because the tools were written with MBR disks in mind and then adapted for GPT disks.)

To partition for an EFI installation, you need:

  • Your normal Linux partitions. Ubuntu's default is for root (/) and swap, but I personally recommend /home, as well. There's nothing unusual about setting these up on GPT vs. MBR, except for the aforementioned lack of distinction between primary, extended, and logical partitions.
  • An EFI System Partition (ESP), which is a FAT32 partition with a particular type code. This type code is denoted differently depending on the partitioning tool you use. In GPT fdisk (gdisk, sgdisk, and cgdisk), it's got a type code of EF00. In parted and GParted, it's got its "boot flag" set. (Note that in these programs, the "boot flag" on a GPT disk has nothing to do with a "boot flag" on an MBR disk.) In Ubiquity, IIRC the ESP is called an "EFI boot partition," but I might be misremembering the term. The EFI specification says nothing about the size of the ESP, but I recommend making it 550MiB.

When you set up your computer, you can share a single ESP between multiple OSes. If you prefer, you can create multiple ESPs, one for each OS or distribution; however, Windows tends to get confused by that, so if you plan to install Windows in the future, it's best to stick with one ESP. Be absolutely positive that you do not erase the ESP when you install a second or subsequent OS; if you do, you'll wipe out the boot loader(s) for earlier OSes. In fact, I recommend backing up the ESP after each OS installation so that you can restore it in case of an accident. A file-level backup (copying files with cp or in a file manager, or creating a tarball or .zip file) should be sufficient.

If you prepare your partitions ahead of time, be sure to tell Ubiquity that the ESP is the ESP. IIRC, you've got to click the "Change" button and tell the program to use the ESP as an "EFI boot partition." If you don't do this, you may find that the boot loader doesn't install, or the program may refuse to continue; I don't recall precisely what happens.

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