On Thursday 2021-03-11 23:43, Frank Scheiner wrote:
>> Do you know if I can via serial-console reset the system?
> Reset from the serial console might work via the kernel with the [magic
> system request] functionality.
> [magic system request]:
> https://www.kernel.org/doc/html/v4.11/admin-guide/sysrq.html
> But you can always reset the system using the SC. The T1000 (and the
> T2000, too) has both serial (on T2000 right of the DB-9 ttya port,
> should work with a blue Cisco serial cable) and network port (on T2000
> above the two USB ports). The serial port of the SC automatically
> switches to the system console after some (configurable) time

SER MGT is a RS232-ish serial line, just with a RJ-45 connector for size.
Once the SC has finished booting, system console is the default mode.
Since SER has no notion of connections, it should be staying in whatever mode
it was left in. Maybe there is a autoswitch, but I never observed it (but I
would not want to wait a lot of minutes either just to observe it).

For NET MGT, when you start a new SSH connection, it always starts
out in system console mode and #. is needed.

>> I tried sending a break on the serial console, but the errors just keep
>> running.
>> Break is received, since I see it as SC Alert, but I am not put into the
>> console, maybe there is some further trick on these newer machine?
> So you already got access to the SC. Then you can reset the machine from
> there, too.

Because NET does not have an equivalent of the serial pin used to traditionally
signal "break", a synthetic break can be issued from SC. But it's a bit
awkward, because you immediately need to go back into system console mode to
type the desired sysrq character.

sc> break
confirm (y/n)y
sc> console
confirm (y/n)y
type <<S>>
Linux kernel: ah yes I received SYSRQ-s

>> I am
>> used to old SparcStations and UltraSparc Netras, where it was sufficient.
>> It is inconvenient at every hang to power-cycle, since at every turn on,
>> it runs a self-test which lasts minutes :)
> I think depending on the SC configuration, these machines also run a
> self-test for every X resets, but this should be configurable.

It's the first thing you want to turn off as a private user.

        diag_trigger none

and probably

        diag_mode off

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