A text listing of the filesystems which were compiled into the kernel. Incidentally, this is used by mount(1) to cycle through different filesystems when none is specified. The "nodev" string in the first column means that filesystem does not require a block device to be mounted, it's so called virtual filesystem.

Example output:

nodev   sysfs
nodev   rootfs
nodev   bdev
nodev   proc
nodev   cpuset
nodev   debugfs
nodev   sockfs
nodev   pipefs
nodev   futexfs
nodev   tmpfs
nodev   inotifyfs
nodev   eventpollfs
nodev   configfs
nodev   devpts
nodev   ramfs
nodev   hugetlbfs
nodev   fuse
nodev   fusectl
nodev   mqueue
nodev   kvmfs
nodev   oprofilefs