AW: Pygrub does not boot ext2 on LVM volume other than from root directory

[Klaus Darilion <klaus.darilion@xxxxxx>]

Hi!

Not sure if this is related to your problem. But we noticed that the boot 
partition must be the first one in the disk section:
root        = '/dev/xvda2 ro'
disk        = [
                  'phy:/dev/vg0/vm-disk,xvda2,w',
                  'phy:/dev/vg0/vm-swap,xvda1,w',
              ]

Regards
Klaus

> -----Ursprüngliche Nachricht-----
> Von: Xen-users <xen-users-bounces@xxxxxxxxxxxxxxxxxxxx> Im Auftrag von
> Martin Lang
> Gesendet: Sonntag, 7. Januar 2024 10:17
> An: xen-users@xxxxxxxxxxxxxxxxxxxx
> Betreff: Pygrub does not boot ext2 on LVM volume other than from root
> directory
> 
> Hi all,
> 
> I have a weired problem with pygrub.
> 
> The machine I am running xen is a PC-Engines APU for which I build xen
> and tools using Yocto project. Version of Xen 4.16 stable from the
> "Kirkstone" branch of Yocto.
> 
> Everything went well and I was able to install the image on a LVM
> Volume. Hypervisor runs well. I created separate logical volumes for
> DomU guests and installed Debian on it. I am also able to boot the DomU
> guest as long as I copy the kernel and initrd.img to the Dom0
> filesystem and use the "kernel=" parameter in the xen.cfg file.
> 
> When I try to use pygrub to boot the guest it tells that it does not
> find a partition containing a kernel. With a little investigation I
> found out, that it is not a parsing problem of grub.cfg but it does not
> find grub.cfg at all.
> 
> So I compiled the libfsimage with debug information (-DE2DEBUG in
> Makefile) and found out, that the libfsimage does not recurse into the
> directories. It finds /boot at the root directory but does not recurse
> into it while it looks for /boot/grub/grub.cfg.
> 
> When I mount the volume and filesystem directly using xl-attach
> everthing is o.k. so the filesystem itself seems to be o.k.
> 
> I also created a dummy menu.lst file at root directory. Interestingly
> pygrub the finds it, is able to parse it, shows the menu and then fails
> when he tries to find the kernel because then he has to recurse into
> /boot directory again.
> 
> Next test was, that i copied kernel and initrd directly into the root
> directory and refered to a menu.lst also in root directory. Now pygrub
> finds everything and starts the DomU.
> 
> 
> Any ideas, what the problem is?
> 
> 
> If it helps I copy the output of the Debug (E2DEBUG flag set):
> >fsblock 8737 buffer c2ef0f40
> >directory entry ino=23
> >entry=libx32
> >dirname=boot, rest=, loc=200
> >ed 41 00 00 00 10 00 00 1a fe 97 65 1c fe 97 65
> >1c fe 97 65 00 00 00 00 00 00 12 00 08 00 00 00
> >00 00 08 00 44 01 00 00 0a f3 01 00 04 00 00 00
> >00 00 00 00 00 00 00 00 01 00 00 00 21 22 00 00
> >00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >00 00 00 00 00 00 00 00 00 00 00 00 04 72 00 00
> >logical block 0
> >fs block=8737
> >fsblock 8737 buffer c2ef0f40
> >directory entry ino=8193
> >entry=boot
> >inode 8193
> >dirname=/grub/grub.cfg
> >ipg=8192, dpb=128
> >group_id=1 group_desc=0 desc=1
> >fsblock 1 buffer c2eeeec0
> >gdp=c2eeeec0, inodes_per_block=16, inode_offset=0
> >inode table fsblock=0
> >fsblock 0 buffer c2eefec0
> >ipb=16, sizeof(inode)=256
> >inode=c2eefec0, raw_inode=c2eefec0
> >offset into inode table block=0
> >00 first word=0
> >first word=0
> >Bad filetype: Size:0, Mode:0, IsDir:0
> >inode 2
> >dirname=/grub/grub.cfg
> >ipg=8192, dpb=128
> >group_id=0 group_desc=0 desc=0
> 
> As one can see, it goes through the root directory. In the output I
> deleted the beginning. On top of the trace it looks at INODE libx32 and
> looking for an entry called "boot". That is correct so far. Next if
> finds "boot". INODE number 8193 is also correct (checked with debugfs)
> and tries to recurse down and look for /grub/grub.cfg.
> But now something seems to go wrong. Instead of the next INODE it sees
> only 00.
> 
> 
> Any help is highly appreciated.
> 
> Regards Martin