I am using VMware ESXi vSphere 5.0.0 and mounting a 6TB LUN from my Dell EqualLogic SAN. I am presenting the LUN using RDM (Raw Device Mappings) so as to be able to see all 6 TBs. So far, so good.

Then I use Gparted to create multiple partitions, several of which are over 2TBs in size. I used "gpt" to create the initial partition table. I am able to flag the /boot partition to be bootable. Again, so far, so good.

Next, I boot into CentOS 6.2 64-bit and label each partition as I defined it under the Gparted Live CD. No problem. I ran the install and everything installed just fine. Now... when I reboot, the VM under ESXi says no operating system found.

My question: how to make the bootable partitions discoverable and boot into my CentOS 6.2 install? I tried editing the firmware under ESXi to be EFI rather than BIOS, and then nothing worked.

  • Switching to EFI after the OS is installed won't work - try installing the OS now that you're set to EFI (which, as you've discovered, is required for booting to a GPT-partitioned disk). – Shane Madden May 16 '12 at 22:03
  • @ShaneMadden, EFI is not required for booting a gpt disk, grub2 can be installed and boot from one in bios mode. You need to create a 1mb bios_grub partition and a /boot partition under the 2gb mark though. – psusi May 17 '12 at 0:51

You could make your life much easier by creating a 500MB LUN dedicated to /boot and your bootloader. If you don't want to take that approach, a dedicated LUN of few gigabytes for /boot, your bootloader and system. There's little value if any in using the same LUN for your system and data, and you get into complications if you ever want to resize the LUN (reboots needed as the partitions cannot be dynamically expanded due to some tricky problems around write barriers).

Now let's assume you really want to keep a single LUN.

As psusi mentioned, Grub2 will work happily in BIOS mode with a GPT filesystem granted you create a dedicated partition. You can find detailed instructions on the Arch Linux wiki that are not specific to that distribution. Please note the specific partition type.

As Shane covered, if you want to stick to EFI, you should probably have your system running it during the installation procedure. It rather depends on the distribution's installation procedure, unfortunately I don't know much about this version of Anaconda so I can't make any claims.

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