Screenshots are not easily usable, so I tried the "serial ports" feature of VirtualBox.
An "Host Pipe" mode is available, to redirect serial port output to a pipe. But it didn't work by using a named pipe, created with mkfifo. Actually, if set to create the pipe, VirtualBox will create a UNIX local domain socket.
$ file /tmp/vbox-pipe /tmp/vbox-pipe: socket
The "pipe" name is a bit ambiguous, it's easy to understand it as a fifo, not a socket (and actually, the Windows implementation uses a named pipe in VirtualBox...)
This is all explained in VirtualBox's manual (PDF) (section 3.7.9: Serial ports), which even mentions the nice socat utility.
So, to get serial output to stdout, one can use:
socat /tmp/vbox-pipe -
Or to keep serial output in a log file:
socat -u /tmp/vbox-pipe GOPEN:vbox.log tail -f vbox.log
Sometimes, the connection to the socket fails with ECONNREFUSED, so it can be better to create it with socat, before starting the virtual machine:
socat unix-listen:/tmp/vbox-pipe -
Or this way not to close the pipe everytime the virtual host is shut down:
socat unix-listen:/tmp/vbox-pipe,reuseaddr,fork -
Now, I just need to add console=ttyS0 as kernel command line option when booting my live system, and I have no excuse not to report the bugs. I could even try to fix them.
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