Matthias Drochner <drochner@zelux6.zel.kfa-juelich.de> said:
> >   # /usr/mdec/installboot /usr/mdec/biosboot.sym /dev/rsd0a
> >   installboot: not enough fragment space in bootcode
>
> In your case, root filesystem fragmentation (and perhaps
> a small filesystem block size) cause that more chunks
> are needed.

Yes, the block size is small.  The filesystems on this disk were built
a long time ago, maybe in the NetBSD 0.9 era.  Disk space was
expensive, and I had lots of little files, so a 512/4096 filesystem
made a lot of sense at the time.  Here's the disklabel information for
the root partition:

#        size   offset    fstype   [fsize bsize   cpg]
  a:   626688    63488      4.2BSD      512  4096     0   # (Cyl.   31 - 336)

> "installboot" catches this case, so you keep the old bootblocks.

I greatly appreciate this. :-)

> Space is not that scarce in the disk bootblocks, and the table
> is easily extended, so I'll increase the default size.
> I'd like to get a figute about a reasonable value.
> Can you:
> -uncomment the line with "MAXFLENTRIES" in
>    i386/stand/biosboot and rebuild
> -install the resulting bootblock with the "-v" option and
>   mail me the output?

Yes:

  # /usr/mdec/installboot -v /usr/mdec/biosboot.sym /dev/rsd0a
  /usr/mdec/biosboot.sym: entry point 0
  proto bootblock size 30208
  room for 10 filesystem blocks at 0x4c0
  renamed //boot -> //boot.bak
  Will load 44 blocks.
  dblk: 13656, num: 8
  dblk: 13672, num: 8
  dblk: 13688, num: 8
  dblk: 13704, num: 8
  dblk: 13720, num: 8
  dblk: 13595, num: 4
  BSD partition starts at sector 63488
  deleting //boot.bak
  #

After doing this, I successfully rebooted.  Thanks!
-- 
Andreas Gustafsson, gson@araneus.fi