Do you run Mac OS X and ZSH? Does your shell spew out readlink errors for some commands? Like this? $ umount /Vo*tab*readlink: illegal option -- q usage: readlink [-n] [file ...] readlink: illegal option -- q usage: readlink [-n] [file ...] readlink: illegal option -- q usage: readlink [-n] [file ...] ... That’s because ZSH assumes you’ve got the GNU version of readlink. Install that version with