chroot_ssh_trick

chroot SSH Trick

This technique allows LabVIEW to run commands outside of its chroot on a LINX BeagleBone Black or Raspberry Pi target. This can be useful for interacting with commands that are unavailable inside the chroot like raspistill.

1. Install an ssh client to your chroot:
   • sudo schroot -r -c lv
   • opkg update
   • opkg install openssh-ssh
   • exit
2. Configure pub key authentication so you don't have to type in a password interactively (Hint: This let's you use the ssh client from LabVIEW System Exec VI).
   • ssh-keygen -t rsa
     • stick with the defaults when it prompts you, especially when it asks for the passphrase; we want an empty passphrase
   • cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
   • sudo mkdir /srv/chroot/labview/root/.ssh
   • sudo cp ~/.ssh/id_rsa* /srv/chroot/labview/root/.ssh/.
3. Now log back into the chroot and run the ssh command once so that you can add localhost to the list of known hosts
   • sudo schroot -r -c lv
   • ssh root@localhost ls
     • When prompted to add localhost to the list of known hosts, say yes
   • exit
4. At this point you can run commands from within the LV chroot in the system outside the chroot by running a command of the form ssh <root_user>@localhost <command>. For instance, if I wanted to check the version of the Debian operation system on a Raspberry Pi I would run ssh pi@localhost cat /etc/debian_version. These commands can be run in a LabVIEW VI by using the System Exec VI, so now you have a way to execute commands outside of the LV chroot.