I'm trying to alter nmbclusters on 2.0_STABLE in the same as I've been 
doing for years on 1.6.2 and earlier, but it's dumping core (on GENERIC 
and pretty-much GENERIC kernels):

  1# gdb --write /netbsd
GNU gdb 5.3nb1
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386--netbsdelf"...(no debugging symbols found)...
(gdb) set nmbclusters=4096
(gdb) quit
Segmentation fault(core dumped)
  2#

Here's the backtrace from gdb.core

(gdb) bt
#0  0x08125bda in _bfd_elf_strtab_emit ()
#1  0x08122e3c in _bfd_elf_write_object_contents ()
#2  0x0812dca4 in bfd_close ()
#3  0x08081b5a in exec_close ()
#4  0x080f43eb in quit_force ()
#5  0x08060c0e in do_cfunc ()
#6  0x080624ea in cmd_func ()
#7  0x080f30cc in execute_command ()
#8  0x08080e86 in command_handler ()
#9  0x080812a6 in command_line_handler ()
#10 0x4821ac6e in rl_callback_read_char () from /usr/lib/libedit.so.2
#11 0x0808082b in rl_callback_read_char_wrapper ()
#12 0x08080d9e in stdin_event_handler ()
#13 0x08080163 in handle_file_event ()
#14 0x0807fc63 in process_event ()
#15 0x0807fcac in gdb_do_one_event ()
#16 0x080f2da2 in do_catch_errors ()
#17 0x080f2d04 in catcher ()
#18 0x080f2dd8 in catch_errors ()
#19 0x0807fccf in start_event_loop ()
#20 0x080b0a9e in captured_command_loop ()
#21 0x080f2da2 in do_catch_errors ()
#22 0x080f2d04 in catcher ()

-- 
Stephen