Doc suggestion: FAQ / copy large sparse files to dom0

[ghost]

Even if not recommended, document how to copy large sparse files to dom0 (eg. imported VM images).

related ML post: https://groups.google.com/forum/#!searchin/qubes-users/sparse$20tar|sort:date/qubes-users/aDtUgRFtCAE/AQypJpaPBgAJ

Cat the whole file and then only resparse it after the transfer.

qvm-run --pass-io tempDebian 'cat "/home/user/meta.raw"' | dd
conv=sparse of=/var/lib/qubes/appvms/metasploitable/root.img

That's the most secure way but it will take some time to copy the file. Alternatively, one could pipe the output of tar -Scf - large_file to dom0 and then untar the resulting file but this is not recommended since an attacker could use potential vulnerabilities in tar to compromise dom0

[edit - this suggestion is a bit controversial, so no problem to reject it ; that way we'll test "rejection" workflows :) ]

[ghost]

closing - instructions are in https://github.com/Qubes-Community/Contents/blob/master/docs/common-tasks/copying-files-to-dom0.md