EFI/ZFS Update: successful tests, need more complex vdevs

[Eric McCorkle]

On 01/15/16 06:51, Renato Botelho wrote:
>> On Jan 15, 2016, at 00:41, Steven Hartland <killing at multiplay.co.uk> wrote:
>>
>> Just wanted to let everyone know that I just finished committing these changes to the tree.
>>
>> Huge thanks to Eric's for his work on this, as well as everyone else who contributed.
>>
>> I've set the target for MFC of 2 weeks, so I hope to be able to get this into stable/10 before the 10.3 slush, so if you're interested in this change please test a head build > r294068 ASAP.
>
> Great work, thanks!
>
> Is there a way to move a installed ZFS system to EFI?
>

(Refer to Steven's guide for the simple case where you can create an EFI 
partition)


== Using GRUB ==

GRUB can be used with loader.efi on a ZFS system (I use this myself, as 
I have a Gentoo install in the same ZFS volume)

Make sure you install GRUB with EFI support (the ports collection will 
handle this).  The grub port comes with a script that auto-detects 
filesystems and sets up a grub.cfg in /boot/grub/.  However, that script 
won't properly detect ZFS partitions, so you'll need to add it manually. 
  The entry is simple.

I have a zfs volume called "data", which has the freebsd system root on 
the filesystem data/freebsd.  The GRUB entry then is:

menuentry "FreeBSD" {
   search.fs_label data ZFS_PART
   chainloader ($ZFS_PART)/freebsd@/boot/loader.efi
}

The first line searches for the volume "data" and binds its device to 
the variable ZFS_PART.  The second specifies that the chained bootloader 
is under the filesystem "freebsd" (the @ at the end of the name denotes 
a filesystem, not a path), with the path /boot/loader.efi


== Disks without enough space to make the GPT or EFI partition ==

If you have a ZFS filesystem on an MBR disk, or on a GPT disk without 
enough space to create a workable EFI partition, you can use one of 
ZFS's lesser-known features: zfs send/recv.

ZFS send and recv allow an entire filesystem to be serialized out to a 
stream, and then read back in.  You can use this to dump the entire 
filesystem out to a removable storage or an NFS mount.  Then, use an 
install disk or memstick and repartition your drive, using zfs recv to 
recreate the filesystem.


== On a Mac ==

(Note: this is based on research that is several years old at this 
point.  Also, I never actually field tested this myself.)

Macs are wierd, due to their non-standard EFI.  The Mac EFI 
implementation looks for an HFS+ partition, and loads the "blessed" file 
as the EFI bootloader (this is a special filesystem-level metadata 
unique to HFS+ filesystems).

In order to do an EFI boot on a mac, you'd need some way of 
manufacturing an HFS+ partition containing only your bootloader, with 
that file being "blessed".  The easiest way to do this would be to use a 
Mac OS install to create an empty HFS+ filesystem, add your boot loader, 
then use a shell command to "bless" it (this command exists, but I don't 
remember what it is offhand).  It also wouldn't be too hard to write a 
tool to create an HFS+ image from a file (I have a half-written 
implementation of that lying around somewhere).

Also note that Macs expect a 200MB EFI partition (which isn't actually 
used for anything), and I've heard reports of the firmware flaking out 
if it's not there.

I believe there are also GRUB and rEFIt options for Mac, if you don't 
want to go to these lengths.