Somewhat uniquely among illumos distributions, Tribblix doesn't require installation to ZFS - it allows the possibility of installing to a UFS root file system.
I'm not sure how widely used this is, but it will get removed as an option at some point, as the illumos UFS won't work past Y2038.
I recently went through the process of testing an install of the very latest Tribblix to UFS, in a bhyve guest running UEFI. The UEFI part was a bit more work, and doing it clarified how some of the internals fit together.
(One reason for doing these unusual experiments is to better understand how things work, especially those that are handed automatically by more mainstream components.)
OK, on to installation.
While install to zfs will automatically lay out zfs pools and file systems, the ufs variant needs manual partitioning. There are two separate concerns - the Tribblix install, and UEFI boot.
The Tribblix installer for UFS assumes 2 things about the layout of the disk it will install to:
- The slice s0 will be used to install the operating system to, and mounted at /.
- The slice s1 will be used for swap. (On zfs, you create a zfs volume for swap; on ufs you use a separate raw partition.)
It's slightly unfortunate that these slices are hard-coded into the installer.
For UEFI boot we need 2 other slices:
- A system partition (this is what's called EFI System partition, aka ESP)
- A separate partition to put the stage2 bootloader in. (On zfs there's a little bit of free space you can use; there isn't enough on ufs so it needs to be handled separately.)
The question then arises as to how big these need to be. Now, if you create a root pool with ZFS (using zpool create -B) it will create a 256MB partition for ESP. This turns out to be the minimum size for FAT32 on 4k disks, so that's a size that should always work. On disks with a 512 block size, it needs to be 32MB or larger (there's a comment in the code about 33MB). The amount of data you're going to store there is very much less.
The stage2 partition doesn't have to be terribly big.
So as a result of this I'm going to create a GPT label with 4 slices - 0 and 1 for Tribblix, 3 and 4 for EFI system and boot.
There are 2 things to note here: First,the partitions you create don't have to be laid out on disk in numerical order, you can put the slices in any order you want. This was true for SMI disks too, where it was common practice in Solaris to put swap on slice 1 at the start of the disk with slice 0 after it. Second, EFI/GPT doesn't assign any special significance to slice 2, unlike the old SMI label where slice 2 was conventionally the whole disk. I'm avoiding slice 2 here not because it's necessary, but so as to not confuse anyone used to the old SMI scheme.
The first thing to do with a fresh disk is to go into format, invoked as format -e (expert mode in order to access the EFI options). Select the disk, run fdisk from inside format, and then install an EFI label.
format -e
#
# choose the disk
#
fdisk
y - to accept defaults
l - to label
1 - choose efi
Then we can lay out the partitions. Still in format, type p to enter the partition menu and p to display the partitions.
p - enter partition menu
p - show current partition table
At this point on a new disk it should have 8 as "reserved" and 0 as "usr", with everything else "unassigned". We're going to leave slice 8 untouched.
First note where slice 0 currently starts. I'll resize it at the end, but we're going to put slices 3, 4, and 1 at the start of the disk and then resize 0 to fill in what's left.
To configure the settings for a given slice, just type its number.
Start with slice 3, type 3 and configure the system partition. This has to use the "system" tag.
tag: system
flags: wm (just hit return to accept)
start: 34
size: 64mb
Type p again to view the partition table and note the last sector of slice 3 we just created, and add 1 to it to give the start sector of the next slice. Type 4 to configure the boot partition, and it must have the tag "boot".
tag: boot
flags: wm (just hit return to accept)
start: 131106
size: 16mb
Type p again to view the partition table, take note of the last sector for the new slice 4, and add 1 to get the start sector for the next one. Which is 1 for the swap partition.
tag: swap
flags: wm (just hit return to accept)
start: 65570
size: 512mb
We're almost done. The final step is to resize partition 0. Again you get the start sector by adding 1 to the last sector of the swap partition you just created. And rather than giving a size you can give the end sector using an 'e' suffix, which should be one less than the start of the reserved partition 8, and also the last sector of the original partition 0. Type 0 and enter something like:
tag: usr
flags: wm (just hit return to accept)
start: 1212450
size: 16760798e
Type 'p' one last time to view the partition table, check that the Tag entries are correct, and that the First and Last Sectors don't overlap.
Then type 'l' to write the label to the disk. It will ask you for the label type - make sure it's EFI again - and for confirmation.
Then we can do the install
./ufs_install.sh c1t0d0s0
It will ask for confirmation that you want to create the file system
At the end it ought to say "Creating pcfs on ESP /dev/rdsk/c1t0d0s3"
If it says "Requested size is too small for FAT32." then that's a hint that you need the system partition to be bigger. (An alternative trick is to mkfs the pcfs file system yourself, if you create it using FAT16 it will still work but you can get away with it being a lot smaller.)
It should also tell you that it's writing the pmbr to slice 4 and to p0.
With that, rebooting into the newly installed system ought to work.
Now, the above is a fairly complicated set of instructions. I could automate this, but do we really want to make it that easy to install to UFS?
