Why can't GnuCash find my data file anymore?

We're very sorry, but you just shot yourself in the foot. GnuCash uses $HOME/.gnucash to store metadata files. In particular, $HOME/.gnucash/books stores metadata about your data files. In versions 1.8 and earlier the metadata file was named as the encoded name of the full path to your datafile, but as of 2.0 this was changed and the metadata file is just named the same as the data file. So if you saved your data file into $HOME/.gnucash/books and updated your versions, GnuCash just overwrote your data file with the metadata file. You'll need to copy a backup file and move it somewhere outside of $HOME/.gnucash and tell GnuCash to look there by using the File -> Open feature to load the new datafile.  more