LinuxQuestions.org - Hard Drives and UEFI

Hi,

Quote:

Originally Posted by tb75252 (Post 5076775)

This is a question from somebody who is not much of a computer expert...

It is my understanding that UEFI stores all information about initialization and startup in an .efi file located on the HD, inside a special partition.

So, if I were to install a brand-new HD and get rid of the old one, I first would have to find a way to backup this special partition, correct?

Is this a job that Clonezilla can handle, or do I need some other utility?

Your understanding is correct. '.efi' information is the 'UEFI' firmware that is then provided to allow the boot process from a bootloader;

Quote:

Excrpt from 'UEFI';
UEFI has support for reading both the partition table as well as understanding filesystems. Hence it is not limited by 440 byte code limitation (MBR boot code) as in BIOS systems. It does not use the MBR boot code at all.
The commonly used UEFI firmwares support both MBR and GPT partition table. EFI in Apple-Intel Macs are known to also support Apple Partition Map besides MBR and GPT. Most UEFI firmwares have support for accessing FAT12 (floppy disks), FAT16 and FAT32 filesystems in HDDs and ISO9660 (and UDF) in CD/DVDs. EFI in Intel Macs can also access HFS/HFS+ filesystems, in addition to the mentioned ones.
UEFI does not launch any boot code in the MBR whether it exists or not. Instead it uses a special partition in the partition table called EFI System Partition in which files required to be launched by the firmware are stored. Each vendor can store its files under <EFI SYSTEM PARTITION>/EFI/<VENDOR NAME>/ folder and can use the firmware or its shell (UEFI shell) to launch the boot program. An EFI System Partition is usually formatted as FAT32 or (less commonly) FAT16.
Under UEFI, every program whether it is an OS loader or a utility (e.g. a memory testing app or recovery tool), should be a UEFI Application corresponding to the EFI firmware bitness/architecture. The vast majority of UEFI firmwares, including recent Apple Macs, use x86_64 EFI firmware. The only known devices that use IA32 (32-bit) EFI are older (pre 2008) Apple Macs, some Intel Cloverfield ultrabooks and some older Intel Server boards are known to operate on Intel EFI 1.10 firmware.
An x86_64 EFI firmware does not include support for launching 32-bit EFI apps (unlike x86_64 Linux and Windows versions which include such support). Therefore the UEFI application must be compiled for that specific firmware processor bitness/architecture.

Simplified boot process;

Quote:

Excerpt from 'UEFI';
Boot Process under UEFI

System switched on - Power On Self Test, or POST process.
UEFI firmware is loaded. Firmware initializes the hardware required for booting.
Firmware then reads its Boot Manager data to determine which UEFI application to be launched and from where (i.e. from which disk and partition).
Firmware then launches the UEFI application as defined in the boot entry in the firmware's boot manager.
The launched UEFI application may launch another application (in case of UEFI Shell or a boot manager like rEFInd) or the kernel and initramfs (in case of a boot loader like GRUB) depending on how the UEFI application was configured.
Note: On some UEFI systems the only possible way to launch UEFI application on boot (if it does not have custom entry in UEFI boot menu) is to put it in this fixed location: <EFI SYSTEM PARTITION>/EFI/boot/bootx64.efi (for 64-bit x86 system)

Hope this helps.