The QNAP TS-XXX NAS boxes are nice little systems but one thing I really miss is a console. Martin Michlmayr has some instructions (TS-119, TS-219, TS-41x) on his excellent Debian On QNAP pages on how to build a suitable adaptor but sadly even though I've managed to get all the parts I've been too lazy to actually solder the thing together (it doesn't help that I nearly always burn myself when I use a soldering iron!).

This became more pressing when someone reported that Debian bug #693263 in qcontrol was not fixed in Wheezy since the issue appeared to be in the initramfs hook. Worse it seemed like something in my proposed fix was causing the system to not boot at all!

Having finally found the hardware needed to reproduce the issue my first thought was to try netconsole. To do this I edited /etc/initramfs-tools/modules to add:

      mv643xx_eth
      netconsole netconsole=@<IP>/eth0,@<DST-IP>/<DST-MAC>

The option syntax is described in netconsole.txt but briefly: <IP> is the address of the TS-419P II I'm debugging on, and <DST-IP> and <DST-MAC> are the IP and MAC address of another machine on the network.

Having done that, running update-initramfs -u and rebooting I can use netcat -u -l -p 6666 on the other machine to see all the kernel messages.

So far so good but this doesn't get me any debugging from the userspace portions of the initramfs. To get those we have to get a bit hacky by editing /usr/share/initramfs-tools/init, first to change:

     # Parse command line options
    -for x in $(cat /proc/cmdline); do
    +for x in $(cat /proc/cmdline) debug; do
            case $x in

and secondly:

             debug)
                     debug=y
                     quiet=n
    -                exec >/run/initramfs/initramfs.debug 2>&1
    +                exec >/dev/kmsg 2>&1
                     set -x
                     ;;

The first of these simulates adding debug to the kernel command line (which can't otherwise easily be edited on these systems) and the second redirects the initramfs process's output to the kernel log. The overall effect is that the output of the initramfs processes appears over netcat.