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Re: Black screen / X issue fixed

Cyril Brulebois <kibi@debian.org> writes:

> Hi,
> Philip Hands <phil@hands.com> (2017-08-14):
>> Yes that's the behaviour I was commenting on in IRC, and which was
>> obviously being spotted by the jenkins/cucumber setup.
> Sorry, based on earlier comments over the previous days/weeks, I went
> for a “X is broken” shortcut and might not have actually got your exact
> point.
>> BTW It is possible to run get something like shell access to the
>> running d-i via its ttyS0 (by putting rather a lot of stuff on the
>> kernel boot command line), so if that would help I can run tests for
>> you and/or explain the proceedure.
> If you would have a little time to explain this, that would be immensely
> useful. Feel free to just sum it up quickly in an email, I might write
> some docs about it afterwards.

Well, it's a bit horrible, but as long as you don't need to type the
kernel command line by hand it's OK.

The code that does the trick is here:


which you can see the result of at about 27 seconds into this:


What that does is start a while loop that reads from /dev/ttyS0, and
runs the commands that you type, returning the STDOUT, STDERR, and
result code, separated by various control characters which you probably
don't care about.

If you do that, then you can use nc (or whatever) to connect to the TCP
port which is defined for the KVM's ttyS0, and type commands, and get
their output, followed by a result code.  It's almost like having a shell
prompt, other than the slightly odd ordering of STDERR and the result.

It would probably be better to have a udeb that contains a thing for
running the listener, like the debugging thing that is available in
tails -- theirs returns results in json, and lets one run as users other
than root, and can drop thing into the background, but we don't really
need all that in d-i.

Cheers, Phil.
|)|  Philip Hands  [+44 (0)20 8530 9560]  HANDS.COM Ltd.
|-|  http://www.hands.com/    http://ftp.uk.debian.org/
|(|  Hugo-Klemm-Strasse 34,   21075 Hamburg,    GERMANY

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