Newfs

When a partition is set up with disklabel and one wants to use this partition as a filesystem the filesystem must first be created. The newfs command does this.

To see what superblocks were written to an already newfs'd filesystem one can use newfs -N on OpenBSD:

# newfs -N /dev/rwd0a
Warning: cylinder groups must have a multiple of 2 cylinders
/dev/rwd0a:     2097648 sectors in 2081 cylinders of 16 tracks, 63 sectors
        1024.2MB in 7 cyl groups (328 c/g, 161.44MB/g, 20608 i/g)
super-block backups (for fsck -b #) at:
 32, 330720, 661408, 992096, 1322784, 1653472, 1984160,

This shouldn't wreck the filesystem in case, but just in case the author dump(8)'ed this filesystem in case this hypothesis was wrong. All good 5 minutes later, whew.

In Linux the newfs command is called mkfs.