Check file checksum

When you transfer files, you may make sure of the authenticity of data.

To do so, computing a file checksum is useful. Use the "sha256" command :

$ sha256 debian-9.6.0-amd64.qcow2.gz
SHA256 (debian-9.6.0-amd64.qcow2.gz) = 91831ba15446f3ab418ae8a5c2a8ac0d852dc5d43bd595a70b88bd6ea4ded397

Do the same on both ends : the output must be the same.

Notice that on GNU/Linux, sha256 don't exist. Its equivalent is sha256sum.

If you are paranoid, you can go further and check signatures with "signify" tool.