I have set up v7 following [1] and I would like to better understand the process of adding a disk to the environment. Here is what I know: The system has one RP06 with two partitions rp0 and rp3 which correspond to the two block devices rp0, rp3, and the two character devices rrp0, and rrp3. The special files look like so: brw-r--r-- 1 root 6, 0 Dec 31 19:05 /dev/rp0 brw-r--r-- 1 root 6, 7 Dec 31 19:04 /dev/rp3 crw-r--r-- 1 root 14, 0 Dec 31 19:01 /dev/rrp0 crw-r--r-- 1 root 14, 7 Dec 31 19:01 /dev/rrp3 This meshes with the device classes switches in c.c: The block device switch: struct bdevsw bdevsw[] = { ... nulldev, nulldev, hpstrategy, &hptab, /* hp = 6 */ ... } The character device switch: struct cdevsw cdevsw[] = { ... nulldev, nulldev, hpread, hpwrite, nodev, nulldev, 0, /* hp = 14 */ ... } I would like to add another RP disk to the environment. After I attach an RP04/05/06 to the system, what should I use as the major/minor device numbers? To put it differently, it doesn't seem correct to me to use 6,1 for the block device or 14,1 for the character device on the new drive as it's a completely different disk from rp0 and rp3 which are just partitions on the first drive and have 6,0, 6,7, and 14,0, 14,7. If each RP can have 8 partitions and there can be 8 drives, what is the correct major, minor numbers to use with v7 for multiple devices? c.c only lists one vector each for the hp device (one block vector where hp = 6, and one char vector where hp = 15). Thanks, Will [1] Haley, C. B. & Ritchie, D. M. (1979). Setting Up Unix – Seventh Edition (pp. 497-505) in UNIX programmer's manual, Vol. 2, Revised and Expanded Version. Bell Laboratories: NY.