faster booting

[Dan Nelson]

In the last episode (Mar 05), Daniel Feenberg said:
> We have several network services hosted on a FreeBSD system, and want
> it to come up quickly, so that these services (dhcp, nameservice,
> nis, tftp etc) are available when systems are restarting after a
> prolonged power failure.
> 
> That is, several times a year we have multi-hour power failures
> (generally starting at midnight because that is utility maintainance
> time) and our UPSs run out of power. That is OK, but we would like
> the systems to come up when the power returns, without going to the
> server room and restarting systems in a prescribed order.
> 
> In most cases the clients hang because essential services are not
> available, and in most cases the clients do not proceed to boot later
> when the service does become available.
> 
> So, is there advice anywhere about speeding up the boot process? It
> appears that most of the 1 minute 45 seconds to boot our system is
> wait time for checking the existence of non-existant hardware and
> would not be appreciable reduced with a faster CPU or disk. Are there
> kernel options that we could use to avoid this checking? Would
> recompiling the kernel in some specialized way help? Would pico-bsd
> be faster?

If it's a PCI system, removing unused drivers can't hurt, but if a
driver doesn't find a supported PCI ID on the system is usually exits
immediately.  But removing drivers for hardware that you have but don't
use might help more.  I know it takes a few seconds to scan for USB
devices even if none are connected, for example.  You can also set
"kern.cam.scsi_delay=500" in loader.conf to take the settling time for
SCSI devices down to .5 sec instead of 2 sec per bus.  There's probably
a similar tunable for IDE/SATA controllers.  Best thing to do is watch
the console and eliminate drivers (or adjust timeouts) that seem to
cause the scrolling to stop :)
 
> About the only thing I can find is to reduce the 10 second boot screen 
> delay - but we need to cut more than 30 seconds.

There might actually be three boot delays: one from boot0 (the F1,F2,F3
boot menu), boot2 (the bootblock that loads /boot/loader), and the
loader.  You can remove the boot0 timeout with "boot0cfg -t 0" or
simply replace it with a dumb mbr with "fdisk -B".  boot2 can be sped
up by creating a boot.config file in your root directory with "-n" in
it, and you alreay know how to reduce /boot/loader's timeout.

Some of this is documented in the boot0cfg(8) and boot(8) manpages.

-- 
	Dan Nelson
	dnelson at allantgroup.com