Source: http://www.feyrer.de/g4u/#imgcreate
Type "uploaddisk your.ftp.server.com filename.gz" to read out the machine's harddisk (rwd0d), and put it into the "install" account of your FTP server under the given filename. The disk image is compressed (with gzip -9), so maybe use a ".gz" file suffix. You don't have to, though. Before putting the file on the FTP server, the "install" account's password is requested.
If you want to clone your second IDE disk, add it's name on the uploaddisk command line: "uploaddisk your.ftp.server.com filename.gz wd1". Similarly, if you use SCSI instead of IDE disks, use "uploaddisk your.ftp.server.com filename.gz sd0".