On Tuesday, 31 August 2021 20:21:58 BST Neil Bothwick wrote: > On Tue, 31 Aug 2021 14:21:35 -0400, Rich Freeman wrote: > > > If you are multibooting frequently and getting into the UEFI boot > > > menu to change the boot order or running efibootmgr is too much > > > hassle, then a 3rd party boot manager will be useful. Your choice of > > > GRUB, rEFInd, systemd-boot, syslinux, EFI executable image will be > > > installed and loaded/run by the UEFI firwmare from the ESP, with > > > which in turn you will select and load your desired OS. > > > > So, which (if any) of these options supports either: > > > > 1. An EFI partition plus /boot on zfs (with no limitations on pool > > config, ie it can be a root pool). > > 2. An EFI partition that contains everything. > > > > If I want to use grub+EFI with a zfs root it sounds like I'd need TWO > > boot partitions - an EFI partition (FAT32), and a /boot partition > > (anything, but if ZFS it needs to have controlled features). That > > seems even more messy than what I'm doing now. > > systemd-boot and refind both support everything on EFI. I am pretty sure > GRUB does too, but I have no reason to use GRUB with EFI. My setup on > this box is /boot on FAT32 and / (and everything else) on btrfs. I've > also used the same setup with ZFS.
Any boot option on a UEFI MoBo requires an 'EFI System Partition' (ESP), formatted as VFAT. The UEFI firmware boot loader will list/load/run any *.efi software stored in the ESP compatible with the UEFI API, whether this is a boot loader, a kernel with an EFI stub, or some .efi diagnostic application. As long as your boot loader of choice, or kernel image and any initrd contains the requisite fs drivers, there will be no problem mounting and accessing whatever root fs needs to be accessed. GRUB contains a number of ZFS modules to do this job (zfscrypt.mod, zfsinfo.mod, zfs.mod) - not sure about the other boot managers. Typical GRUB installations have /boot/efi mounted on the ESP, with the grubx64.efi image on it, while the rest of the files, vmlinuz symlinks, etc. are on the root partition. Please beware, I have not used zfs to date, only btrfs, so the above merely reflects my understanding rather than in depth experience of the difficulty in managing such a setup.
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