Yesterday, I’m tried to install CentOS 6.4 to my new server IBM X3650 M2 with Minimal CentOS 6.4. My Server has two SAS 15K RPM 146GB and setting up RAID 1 Mode.

The CentOS installer shows up and I starts to setup the partition. When I click next button, it keeps showing “You have not created /boot/efi partition”. So, what is /boot/efi partition ?

My server has UEFI firmware such as IBM X3650 M2, M3…, a replacement for the old BIOS (although it still has support for BIOS-only operating systems).

In BIOS systems, the bootloader is stored inside the MBR, in the zeroth sector of the disk. (The 512-byte MBR reserves 446 bytes for bootstrap code, the rest is used for partition information.) If the bootloader is too large, its MBR “stage1” code usually tries to find “stage2” files in your /boot partition.

In EFI or UEFI systems, the bootstrap code area in MBR is usually empty (most UEFI systems don’t even use MBR for partitioning, preferring GPT). Instead, all bootloaders are stored as ordinary .efi programs in an “EFI system partition”, which is a regular FAT32 partition with a special “partition type” in the partition table. If you have multiple operating systems, they share the same EFI system partition.

Often, UEFI systems have a “boot mode” switch in their settings screen, having options such as “UEFI only”, “Legacy (BIOS) only”, “BIOS, then UEFI”, or something similar.

I must create a /boot/efi/ partition of type VFAT and at least 100 MB in size as the first primary partition.

A /boot/efi/ partition (100 MB minimum) — the partition mounted on /boot/efi/ contains all the installed kernels, the initrd images, and ELILO configuration files.

Where,

vfat — The VFAT file system is a Linux file system that is compatible with Microsoft Windows long filenames on the FAT file system. This file system must be used for the /boot/efi/ partition on Itanium systems.

Note: CentOS 6.4 Minimal CD will not install in UEFI mode
I attempted to use minimal install CD to install on a system which uses UEFI to boot. I get an error “Error 15: File not found” and the system will not boot.

To fix it, You choose some solutions
1. Editing the grub menu item at boot, to load the kernel from /isolinux instead of /images/pxeboot.
2. Use DVD full installation
3. Use CentOS 6.5 Minimal CD

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