grml to the rescue

June 5th, 2009 by Ralf Schlatterbeck

I recently needed to recover data from a “dead” notebook. The only hardware I had available that had a connector for an ATA notebook harddisk was my Soekris net4801. This device doesn’t have VGA on board, so we need to boot GRML with a serial console. First I was unable to get GRML to correctly start a getty process. Meanwhile I’ve found out that the recipe in issue485 of the GRML-Bugtracker does the trick (I’ve modified the console speed to the speed I’m using in the Soekris bootloader):

grml console=tty 1console=ttyS1,38400n8

I had tried console=ttyS1,38400n8 before which doesn’t work. So I added the ssh= boot-options found out via the grml cheatsheet. I could ping the machine but no SSH. Turns out it takes a loooong time until grml starts up the ssh-daemon for two reasons

  • The net4801 is really slow
  • GRML creates new SSH Host-keys before starting up SSH. Thats good. But a newly-started box without a Keyboard has a really small random-number pool, so the box sits there waiting for randomness to happen for generating the keys. So it helps to run several parallel pings to the machine to create some network traffic the timing of which slowly fills the randomness pool …

Turns out that process took several minutes on the Soekris net4801. After waiting I was finally able to log into grml and rescue the data using ddrescue. Thanks GRML!

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