In message <199808210258.TAA02432@shell17.ba.best.com>  Todd Whitesel wrote:
> >I hate rebooting my machine to turn on/off a tape or move it to another machine
> >There is only one thing missing in NETBsd, a command to start/stop a scsi-bus,
> >and you could revommend a save method for switching devices online.
> >(eg. Unixware 7 has this now)
> 
> When I was using/adminning SunOS at my last job, tape drives and CD-ROMs
> were regularly moved around without rebooting machines:
> 
> 	umount (does this guarantee a sync?)
> 	stop-A (suspend the kernel and enter debug firmware with ints masked)
> 	unplug tape/cdrom and fix terminator
> 	'go' (unsuspend the kernel)
> 
> ... and a similar reverse procedure for reconnecting things. I found that
> this worked quite well, and never once observed any fried hardware.

On NetBSD you could go to into ddb. 
On Unixware, if you've loaded the HA extension, there is a command to stop
a scsibus or device.
For stopping the bus (or the device that commadn resides on :-)) ), you
would need to pin it in memory and have it wait for a keystroke or so
to continue. This should be fairly easy to implement as an ioctl to 
the scsibus (or pseudo command to the scsiid of the bus) would just stop the
driver from issuing commands and wait for all running commands to complete.  

> 
> The same technique worked with Solaris2 but could be foiled by "boot -r"
> which would remove the unused device nodes from /dev.

On an HP there is an ioscan which rescans the bus. 

Stefan

BTW.
If we can aggree on something, I'm willing to implement it. 
I'm not asking for features someone else should implement. I just don't want 
to work for the trashcan.

> 
> Todd Whitesel
> toddpw @ best.com

--
Stefan Grefen                                Tandem Computers Europe Inc.
grefen@hprc.tandem.com                       High Performance Research Center
 --- Hacking's just another word for nothing left to kludge. ---