Glo Backup of Glo OS before loading new image

Hi all,

I am the owner of a Glo (by Fnac) and just bought an H2O for my daughter (bol.com)

I would like to replace the picture that is displayed (fnac/bol.com) that is
shown on power-on of both Kobo's.

I guess I can do this when I have opened both readers for telnet.

BUT: Is there a way to backup the OS of the Kobo's before starting to tweak ?