
Are tape device links not in /dev/rmt/ on freeBSD? Hmmm.
Try using -f with tar... I don't think you can specify a destination device or file name without using -f? I could be wrong, I don't use freeBSD.
tar -cvf /dev/ast0 ~
Because you wern't specifying a device or file name with -f, it chose the default device for the system... aka /dev/rsa0. Check the /etc/default/tar file. It contains device name entries to use with tar. Again, I don't know if this file exists on freeBSD
Yours probably has an entry like:
archive0=/dev/rsa0
You can change the file, or as a safety, always use the -f option.
If you get the "tar: no match" again just specify some file on your machine, ie:
tar -cvf /dev/ast0 /etc/hosts
You can also do some "mt" commands to exercise the device, and check if it's even working.
mt -f /dev/ast0 status
Check the man page for mt to get more information.
Good luck
