This file displays a list of the file system types currently supported by the kernel. Sample output from a generic /proc/filesystems file looks similar to the following:

nodev   sysfs 
nodev   rootfs 
nodev   bdev 
nodev   proc 
nodev   sockfs 
nodev   binfmt_misc 
nodev   usbfs 
nodev   usbdevfs 
nodev   futexfs 
nodev   tmpfs 
nodev   pipefs 
nodev   eventpollfs 
nodev   devpts         
	ext2 
nodev   ramfs 
nodev   hugetlbfs         
	iso9660 
nodev   mqueue         
	ext3 
nodev   rpc_pipefs 
nodev   autofs

The first column signifies whether the file system is mounted on a block device. Those beginning with nodev are not mounted on a device. The second column lists the names of the file systems supported.

The mount command cycles through the file systems listed here when one is not specified as an argument.