[oi-dev] [discuss] GPT Partitioning for Illumos/Solaris

[Toomas Soome]

> On 17. Aug 2025, at 04:43, Atiq Rahman <atiqcx at gmail.com> wrote:
> 
> Hi Eric,
> > The "Solaris Root" partition type is relevant to UFS, not ZFS. On UEFI, set s0/p1 to be an ESP, "boot, hidden, esp" flags and format it fat32
> 
> Yep, I have done that quite a while ago. Linux is booting alright with that.
> 
> > your "Solaris Reserved" should be s8/p9, 8Mib, -1MiB from end of disk
> . That's for legacy / MBR partitions. Mine is GPT. I don't need that or any other partition for Solaris. I only need one single partition of zfs / illumos and that's working so far.

It is created automatically on GPT and it is used to store fabricated disk identifier for case the disk does not provide one for itself. It is originating from Solaris and since illumos is fork of Solaris, it is still there. MBR+VTOC setup is using space from ‘alternates’ for the same purpose.

rgds,
toomas

> 
> > /EFI/OpenIndiana/bootx64.efi (copy of loader.efi)
> I put mine on /EFI/Solaris/
> 
> I might try rEFInd in future. Right now, I'm booting everything using Linux's bootloader.
> 
> Thanks, <>
> Atiq <>
> 
> On Thu, Aug 14, 2025 at 8:25 PM Eric J Bowman <mellowmutt at zoho.com <mailto:mellowmutt at zoho.com>> wrote:
>> >
>> > parted > mkpart illumos 767GB 100%
>> >
>> > and then set the partition type to solaris launching,
>> >
>> > $ sudo gdisk /dev/nvme0n1
>> >
>> > (set the GUID to "6A85CF4D-1DD2-11B2-99A6-080020736631" )
>> >
>> 
>> The "Solaris Root" partition type is relevant to UFS, not ZFS. On UEFI, set s0/p1 to be an ESP, "boot, hidden, esp" flags and format it fat32, your "Solaris Reserved" should be s8/p9, 8Mib, -1MiB from end of disk. Your ZFS partition should be set to ZFS for illumos, FreeBSD ZFS for freebsd. Being bootable is a property of the ZFS filesystem, not its partition.
>> 
>> /EFI
>> /EFI/OpenIndiana/bootx64.efi (copy of loader.efi)
>> /EFI/boot
>> 
>> I put rEFInd Plus in /EFI/boot, with a backup of its bootx64.efi in case it gets overwritten.
>> 
>> /EFI/boot/drivers/x64_zfs.efi
>> 
>> This driver will allow rEFInd to stub-load loader64.efi from your ZFS partition on most firmware, some will still need the /EFI/OpenIndiana/bootx64.efi. I don't know if the string "OpenIndiana" is registered, this one is:
>> 
>> /EFI/FreeBSD
>> 
>> That's the gist of multiboot on UEFI, more work if you want more than one illumos or freebsd partition, but they will coexist peacefully.
> 
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