Use "mt", a small command-line utility. (mt is an acronym for "magnetic tape". Ofcourse...)
Here are some examples of how to use mt:
1. "mt -t /dev/st0 status" - Report the current tape status
2. "mt -t /dev/st0 rewind" - Rewind the tape (duh)
3. "mt -t /dev/st0 tell" - Report current block number
See "man mt" for more. WARNING: mt can sometimes appear to "hang" if the tapestreamer exhibits weird behaviour. This can almost always be solved with a kill -9 and then unloading/reloading the SCSI board driver. This is one reason why tapestreamers should go on a separate host adapter whenever possible.