Re: ZFS 2.1.5_1 breaks boot on non zfs-on-root systems

[adrian-bl <adrian-bl@users.noreply.github.com>]

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New comment by adrian-bl on void-packages repository

https://github.com/void-linux/void-packages/issues/37667#issuecomment-1165622712

Comment:
@zdykstra 

> What kernel commandline do you boot your system with?

```
[root@abyss adrian]# cat /proc/cmdline 
BOOT_IMAGE=/boot/vmlinuz-5.18.4_1 root=UUID=976f527a-5bf9-442c-be36-f57d98cd86d3 ro loglevel=4 rd.debug
```

@ahesford 

No, i have `root` specified (see above)


> Also, as zdykstra mentioned, you shouldn't put the ZFS dracut module in your initramfs if you aren't booting a 
> ZFS root.

Well, both systems are a pretty vanilla void installation - just with the ZFS package installed (because my /home is on ZFS). I don't think it is expected that i'd have to blocklist ZFS in dracut in such a configuration.


> this function should set root= to whatever the value is that you specified and leave it alone.

The problem here is that dracut already changed this value before:

So my system sets `root=UUID=976...`, let's look at dracut's `parse-block.sh`:

```
case "$root" in
    block:LABEL=*|LABEL=*)
        root="${root#block:}"
        root="$(echo $root | sed 's,/,\\x2f,g')"
        root="block:/dev/disk/by-label/${root#LABEL=}"
        rootok=1 ;;
    block:UUID=*|UUID=*)
        root="${root#block:}"
        root="${root#UUID=}"
        root="$(echo $root | tr "[:upper:]" "[:lower:]")"
        root="block:/dev/disk/by-uuid/${root#UUID=}"
        rootok=1 ;;
 ```

Once this has run, `root` is set to `block:/dev/disk/by-uid/976...` (i verified that this is the case by booting with `rd.debug`)

Now later (after parse-block.sh but before the rootfs mount)`zfs-lib.sh` executes

```
root=$(getarg root=)
```

which will reset `root` with the value specified on the kernel command line, undoing whatever `parse-block.sh` did and ultimatively confusing the rest of dracut by having `root` set to a value it doesn't understand/expect.

(Also see here for the rd.debug output on how `root` is set/updated (note that this includes the patch i posted above (with xroot)) https://gist.githubusercontent.com/adrian-bl/49f25982d68b2e9ca4907b19ad4ce57b/raw/f72cbd3eb2d0fa461aa14279cf3b1fcb7c76866c/gistfile1.txt)