By the command in the instructions I take it you mean
cp -v /drive1/fids/* /drive0/fids

'Argument list to long' is a limitation in the shells command line parsing/management, IIRC. The fids/* expands to a list of all tunes and tags files - which can be quite a lot. It's normally addressed by copying smaller batches ( ie first all files where the name starts with 1, then those who start with 2 etc...) This has been mentioned on the BBS and should, IMHO, be in the FAQ if it's not. Tony?

cp -auvfx /drive1/fids /drive0/ (and variations) solves this by stepping up one level and then pointing to a single entry, the directory containing all the tunes & tags files, instead of listing all the individual files. cp then recurses down into the directory, the list of files is then managed by cp directly, instead of passing through the shell.

/Michael