Re: redirect console to com0

[Dima Veselov <kab00m%lich.phys.spbu.ru@localhost>]

Hi,

lets take a tour into these things:

Server have serial port and a special option to redirect screen.
When redirection is on - BIOS is instructed to send all data from
screen to serial port. When operating system is loading it try
to open port natively as a device and oops - port is busy. It
is busy (locked or even absent) by BIOS redirection function, which
mangle serial port by its own, because serial port is usually not
a device with ability of concurrent usage.

Consider that remote management is just another computer inside
server, which have serial port connected to server's serial port
and nothing more. That means at least that remote management
do not and may not know anything happening in server - not the
speed of serial port, nor any other information.

BIOS and OS collision is the reason why all such BIOSes have a 
special option that usually named "redirection after POST" This 
option tell BIOS to turn redirection off and free serial port 
upon starting OS, so OS can use it as it wants. This option can 
be named in different ways, you can search through or let us know 
what server model you have to point you out.

If you will turn it off - I expect bootloader will not work 
through remote management, because redirection will be not active
at the moment, however kernel will work (if you added consdev to
boot.cfg and remote management speed is 9600).

You should find option, test it (you can test all BIOS options
in working unix/linux OS by cu). If you can't load any OS but
have consdev in boot.cfg - just try loading it not forgetting
to check serial speed in remote management board settings.

After you manage to load NetBSD kernel you should make this 
permanent - remove consdev from boot.cfg and put com0 option
into bootloader instead. This is done by installboot:

This is regular bootloader options

[root@gloria kab00m]$ installboot -v -e /dev/rraid0a
File system:         /dev/rraid0a
Boot options:        timeout 5, flags 0, speed 9600, ioaddr 0, console pc

This is proper settings for remote management

[root@maia ~]$ installboot -v -e /dev/rld0a 
File system:         /dev/rld0a
Boot options:        timeout 5, flags 0, speed 115200, ioaddr 0, console com0

You can change it this way:

installboot -v -e -o console=com0,speed=115200 /dev/rld0a
(or whatever other speed and hard disk)

Kernel will pick up console settings from bootloader.

PS: I advise to avoid using same ethernet port for server 
and remote management. Not always, but its common for such a
setup to put link down on initialization process. That means 
that you may have lags or even to reconnect your telnet/ssh 
session every time the server is booting up.

On Thu, Apr 26, 2018 at 03:07:29PM +0000, Steve Blinkhorn wrote:
> I'm not clear exactly what you mean here.   I'm still not getting
> redirection once the NetBSD boot sequence gets past the boot.cfg menu
> (the line of numebrs that is the first sign that a kernel is booting
> shows, but is generally truncate), but something changed because whils
> I was originally using the shared LAN port for bot remote management
> and normal usage, I had to connect to the dedicated LAN port because
> the user name and password for the ssh session to the management
> console no longer worked.
> 
> The point of this operation is to be able to do remote fsck in
> single-user mode.   For that I need network access to the console in
> single-user mode.
> 
> --
> Steve Blinkhorn <steve%prd.co.uk@localhost>
> 
> You wrote:
> > 
> > On Thu, Apr 26, 2018 at 03:15:55PM +0200, Martin Husemann wrote:
> > > On Thu, Apr 26, 2018 at 03:12:39PM +0200, Manuel Bouyer wrote:
> > > > You have to tell NetBSD to use the serial port as console.
> > > > You can do this with
> > > > consdev com0
> > > > at boot prompt or in the /boot.cfg file
> > > 
> > > You also want to enable the console entry in /etc/ttys and disable all ttyE*
> > > entries.
> > 
> > Do not forget to set BIOS redirection to "BIOS only" or "off after 
> > POST" mode. This should be used to prevent redirection when OS starts,
> > because OS use native serial console.
> > 
> > -- 
> > Sincerely yours,
> > Dima Veselov
> > Physics R&D Establishment of Saint-Petersburg University
> > 
> 

-- 
Sincerely yours,
Dima Veselov
Physics R&D Establishment of Saint-Petersburg University