I fired up fdisk and got this warning:

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

I didn't even know that my previous Linux installs where DOS-compatible in any way!

What changes?! The man page says nothing about it.

Thanks for answering.


Here is your answer. DOS doesn't allow a partition to start (or end) mid-cylinder. It assumes the partition table is corrupt when it sees this, and not only won't boot off of that partition, it won't boot any partition on the disk.

Basically, unless you're dual-booting, turn DOS compatibility off. Even if you are, unless you're running an old version of DOS/Windows, turn it off.

  • So when fdisk warns me because "Partition 1 does not end on cylinder boundary" is it only about dos compatibility? If I get it well, overlapping cylinders with Linux are OK if sectors are not overlapping? – SamK Jul 16 '10 at 13:11
  • 1
    Actually, Linux will even let you overlap data if you really, really want. It'll probably generate utter gibberish in your FS, and it's certainly not recommended to try it in rw mode, but it's quite possible, and occasionally, albeit rarely, useful (mostly for testing things). – BMDan Jul 16 '10 at 13:22

from googling:


  • I stumbled upon this thread post too. The post of srs5694 seem quite right. But the guy guesses a lot. Is there any "official" documentation? – SamK Jul 16 '10 at 11:19
  • link-only answers are not good – phuclv Nov 20 '18 at 1:16

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