Why does trying to use "mdir" give me "Can't open /dev/fd0: No such file or directory"?

"Update: Your instructions have a typo; it's telling you to make a directory, so you should run mkdir instead of mdir.

""mdir"" is an old tool for accessing DOS-formatted floppy disks without mounting the floppy. You probably don't want that. (It's part of the mtools package, which you are probably safe in uninstalling.)

Are you trying to

make a directory? Use mkdir
remove a directory? Use rmdir
move a directory? Use mv"