sed "s/# 9/9/" MAKEDEV >/dev/MAKEDEV: By default the Makedev script only creates the hda1-hda8 and hdb1-hdb8 devices. By replacing "# 9" by "9"'s in the MAKEDEV script, it will create hda1-hda20, hdb1-hdb20 and possible others (like hdc and hdd) chmod 754 /dev/MAKEDEV: This sets the permissions of the MAKEDEV script to mode 754 which makes it executable only for owner and group and readable by everybody.