I was updating from beta2 to RC1, and during updating Yast already told     
me that an "Error occurred during installation of GRUB", in a dialog box     
with that title but no other textual content, and just an Ok button.    
Then it gave me the option to return to the grub configartion which I did,   
but nothing strange was there (installation into MBR was chosen, like   
expected).  So I Okayed that too, the error came again, I was ignoring it,   
and when I wanted to boot into the updated system I just got an "No operating   
system found".  I had to get to the rescue system and made the following  
observations:  
  
1) when just running "grub" it immediately returned to the shell with return 
   code 1: 
% grub 
% echo $? 
1 
   This means I couldn't use grub for anything, it wasn't accepting any 
   commands, and as shown didn't open the shell.  It turned out that this 
   was because /boot/grub/device.map existed, but was empty (!).  So 
   someone (yast? grub itself?) destroyed it while updating.  I removed 
   it and went on. 
 
2) grub wasn't accepting the commands in /etc/grub.conf, because 
   it mentioned "/dev/sda" in various places, instead of 
   "hd0" as it should have: 
% cat /etc/grub.conf 
root (/dev/sda,1) 
install --stage2=/boot/grub/stage2 /boot/grub/stage1 
(/dev/sda,1) /boot/grub/stage2 0x8000 (/dev/sda,1)/boot/grub/menu.lst 
install --stage2=/boot/grub/stage2 /boot/grub/stage1 
(/dev/sda) /boot/grub/stage2 0x8000 (/dev/sda,1)/boot/grub/menu.lst 
quit 
 
   That it contains two commands is a bit strange, but so be it. 
   So I fixed also that (replaced /dev/sda with hd0), and I was able to 
   reinstall grub via "grub < /etc/grub.conf".  Then I booted, but 
   it still wasn't solved, because: 
 
3) grub started, but didn't find the message file or the kernel, 
   because also /boot/grub/menu.lst contained /dev/sda in places where 
   it needs to use hd0 (I spare us the inline of that file here). 
   So I fixed that too, and _then_ could finally boot into my system. 
 
I will attach the Yast2 logs I gathered during the update.  At the end of 
y2log (where it deals with the bootloader) there are some strange outputs, 
like: 
 
2005-09-08 20:31:14 <2> linux(10149) [agent-ini] 
IniParser.cc(UpdateIfModif):835 Data file '/etc/sysconfig/bootloader' was 
changed externaly! 
2005-09-08 20:31:15 <3> linux(10149) [bash] ShellCommand.cc(shellcommand):78 
249 blocks 
2005-09-08 20:31:15 <3> linux(10149) [bash] ShellCommand.cc(shellcommand):78 
rm:  missing operand 
2005-09-08 20:31:15 <3> linux(10149) [bash] ShellCommand.cc(shellcommand):78 
Try `rm --help' for more information. 
2005-09-08 20:31:15 <3> linux(10149) [bash] ShellCommand.cc(shellcommand):78 
rm: missing operand 
2005-09-08 20:31:15 <3> linux(10149) [bash] ShellCommand.cc(shellcommand):78 
Try `rm --help' for more information. 
2005-09-08 20:31:15 <3> linux(10149) [bash] ShellCommand.cc(shellcommand):78 
311 blocks 
2005-09-08 20:31:15 <1> linux(10149) 
[scr] ../../libscr/src/include/scr/Y2AgentC 
omponent.h(evaluate):108 Evaluating an expression, not SCR builtin