Sometimes you need to be sure no data is remaining on a disk (rm only removes the link to the inode, the data is still on the disk). Here's how you can do it under HP-UX

 1. Check /dev/zero exists. If it doesn't create it with
    mknod /dev/zero c 3 0x00003
 2. Overwrite the disk with zeros as follows:
    dd if=/dev/zero of=/dev/rdsk/device