Look in /dev/fs/9fat.
 [rsc] --rwxrwxr-x M 374841 glenda sys 367 Nov 28 07:08 rc/bin/9fat:
	/n/sourcesdump/2005/1128/plan9/rc/bin/9fat::1,7 - 
	/n/sourcesdump/2005/1129/plan9/rc/bin/9fat::1,7
	  #!/bin/rc
	  
	  rfork e
	- part=`{ls /dev/sd*/9fat >[2]/dev/null}
	+ part=`{ls /dev/fs/9fat /dev/sd*/9fat >[2]/dev/null}
	  if(~ $#part 0) {
	  	echo 'no 9fat partition found' >[1=2]
	  	exit no.9fat