Re: booting at last!

[edmundo@rano.demon.co.uk]

> Funny, you say above that it's ok to put a file system partition on
> cylinder zero (and the silo documentation agrees).  But here you say
> you had to put a non-partition to keep that cylinder blank.

It's a real partition, just unused, namely:

   Device Flag    Start      End   Blocks   Id  System
/dev/sda1             0        1      510   83  Linux native

It occurred to me later that there may be a SILO or boot-floppies bug
here worth correcting at some point ...

One explanation for my experience might be that either SILO installs
itself, by default, into sector 2 of the disc, while the PROM, by
default, boots from sector 2 of the first partition ... or the other
way round. Hence it only worked for me when I made partition 1 start
on cylinder 0. Of course, there are other possible explanations.

The SILO documentation makes some vague allusions to partition 1
starting on cylinder 0, but it's not at all clear why. For example:

  # silo -?
  SILO 0.8.5 Sparc Improved boot LOader
  Usage: /sbin/silo [options]
  Options:
  ...
   -o backup      save your old bootblock from 1st partition if sdX1 doesn't
                  start on cylinder 0 and backup doesn't exist yet
  ...
   -t             store bootblock on the same partition as second stage loader
                  (default is into the bootblock of the whole disk)
  ...
  # zmore /usr/doc/silo/README.gz 
  ...
  
  /sbin/silo will warn you if there are any problems, but you should ensure that:
  
  you need to start either first, or third (usually whole disk), or any other
  partition on cylinder 0 in your partition table.
  ...

My partition 3 did start on cylinder 0, and it was of type "Whole
disk". It didn't work until I also made partition 1 start on cylinder
0. SILO did not warn me about any problems; it simply didn't work when
I rebooted.

Maybe different PROMs follow different rules and that's the reason for
the reigning confusion.

Edmund