1. Miscellaneous operations
    1. Installing the boot manager
      1. fdisk
      2. installboot
    2. Deleting the disklabel
    3. Speaker
    4. Forgot root password?
    5. Password file is busy?
    6. Adding a new hard disk
    7. How to rebuild the devices in /dev

Miscellaneous operations

This chapter collects various topics, in sparse order

Installing the boot manager


Sysinst, the NetBSD installation program, usually installs the NetBSD boot manager on the hard disk. The boot manager can also be installed or reconfigured at a later time, if needed, with the fdisk(8) command. For example:

# fdisk -B wd0

If NetBSD doesn't boot from the hard disk, you can boot it from the installation floppy and start the kernel on the hard disk. Insert the installation disk and, at the boot prompt, give the following command:

> boot wd0a:netbsd

This boots the kernel on the hard disk (use the correct device, for example sd0a for a SCSI disk).

Note: Sometimes fdisk -B doesn't give the expected result (at least it happened to me), probably if you install/remove other operating systems like Windows 95 or Linux with LILO. In this case, try running fdisk -i (which is known as fdisk /mbr from DOS) and then run again fdisk from NetBSD.


There is another tool for installing a bootloader, named installboot(8). Depending on the platform you are using, its usage differs, so you should read the manpage and its extensive EXAMPLES section.

E.g., if you want to install the bootloader for a ffs filesystem to the partition you have your NetBSD in (in this case, sd0c), you would use:

installboot -v /dev/rsd0c /usr/mdec/bootxx_ffs

Deleting the disklabel

Though this is not an operation that you need to perform frequently, it can be useful to know how to do it in case of need. Please be sure to know exactly what you are doing before performing this kind of operation. For example:

# dd if=/dev/zero of=/dev/rwd0c bs=8k count=1

The previous command deletes the disklabel (not the MBR partition table). To completely delete the disk, the whole device rwd0d must be used. For example:

# dd if=/dev/zero of=/dev/rwd0d bs=8k

The commands above will only work as expected on the i386 and amd64 ports of NetBSD. On other ports, the whole device will end in c, not d (e.g. rwd0c).


I found this tip on a mailing list (I don't remember the author). To output a sound from the speaker (for example at the end of a long script) the spkr(4) driver can be used in the kernel config, which is mapped on /dev/speaker. For example:

echo 'BPBPBPBPBP' > /dev/speaker

Note: The spkr device is not enabled in the generic kernel; a customized kernel is needed.

Forgot root password?

If you forget root's password, not all is lost and you can still recover the system with the following steps: boot single user, mount / and change root's password. In detail:

  1. Boot single user: when the boot prompt appears and the five seconds countdown starts, give the following command:

    > boot -s
  2. At the following prompt

    Enter pathname of shell or RETURN for sh:

    press Enter.

  3. Write the following commands:

    # fsck -y /
    # mount -u /
    # fsck -y /usr
    # mount /usr
  4. Change root's password:

    # passwd root
    Changing local password for root.
    New password: (not echoed)
    Retype new password: (not echoed)
  5. Exit the shell to go to multiuser mode.

    # exit

If you get the error Password file is busy, please see the section below.

Password file is busy?

If you try to modify a password and you get the mysterious message Password file is busy, it probably means that the file/etc/ptmphas not been deleted from the system. This file is a temporary copy of the/etc/master.passwd` file; check that you are not losing important information and then delete it:

# rm /etc/ptmp

Note: If the file /etc/ptmp exists you can also receive a warning message at system startup. For example:

root: password file may be incorrect - /etc/ptmp exists

Adding a new hard disk

This section describes how to add a new hard disk to an already working NetBSD system. In the following example a new SCSI controller and a new hard disk, connected to the controller, will be added. If you don't need to add a new controller, skip the relevant part and go to the hard disk configuration. The installation of an IDE hard disk is identical; only the device name will be different (wd# instead of sd#).

As always, before buying new hardware, consult the hardware compatibility list of NetBSD or ask on a mailing list to make sure the new device is supported by NetBSD.

When the SCSI controller has been physically installed in the system and the new hard disk has been connected, it's time to restart the computer and check that the device is correctly detected, using the dmesg(8) command. This is the sample output for an NCR-875 controller:

ncr0 at pci0 dev 15 function 0: ncr 53c875 fast20 wide scsi
ncr0: interrupting at irq 10
ncr0: minsync=12, maxsync=137, maxoffs=16, 128 dwords burst, large dma fifo
ncr0: single-ended, open drain IRQ driver, using on-chip SRAM
ncr0: restart (scsi reset).
scsibus0 at ncr0: 16 targets, 8 luns per target
sd0(ncr0:2:0): 20.0 MB/s (50 ns, offset 15)
sd0: 2063MB, 8188 cyl, 3 head, 172 sec, 512 bytes/sect x 4226725 sectors

If the device doesn't appear in the output, check that it is supported by the kernel that you are using; if necessary, compile a customized kernel (see Compiling the kernel).

Now the partitions can be created using the fdisk(8) command. First, check the current status of the disk:

# fdisk sd0
NetBSD disklabel disk geometry:
cylinders: 8188 heads: 3 sectors/track: 172 (516 sectors/cylinder)

BIOS disk geometry:
cylinders: 524 heads: 128 sectors/track: 63 (8064 sectors/cylinder)

Partition table:
0: sysid 6 (Primary 'big' DOS, 16-bit FAT (> 32MB))
    start 63, size 4225473 (2063 MB), flag 0x0
        beg: cylinder    0, head   1, sector  1
        end: cylinder  523, head 127, sector 63

In this example the hard disk already contains a DOS partition, which will be deleted and replaced with a native NetBSD partition. The command fdisk -u sd0 allows to modify interactively the partitions. The modified data will be written on the disk only before exiting and fdisk will request a confirmation before writing, so you can work relaxedly.

Disk geometries

The geometry of the disk reported by fdisk can appear confusing. Dmesg reports 4226725 sectors with 8188/3/172 for C/H/S, but 8188*3*172 gives 4225008 and not 4226725. What happens is that most modern disks don't have a fixed geometry and the number of sectors per track changes depending on the cylinder: the only interesting parameter is the number of sectors. The disk reports the C/H/S values but it's a fictitious geometry: the value 172 is the result of the total number of sectors (4226725) divided by 8188 and then by 3.

To make things more confusing, the BIOS uses yet another fake geometry (C/H/S 524/128/63) which gives a total of 4225536, a value which is a better approximation to the real one than 425008. To partition the disk we will use the BIOS geometry, to maintain compatibility with other operating systems, although we will lose some sectors (4226725 - 4225536 = 1189 sectors = 594 KB).

To create the BIOS partitions the command fdisk -u must be used; the result is the following:

Partition table:
0: sysid 169 (NetBSD)
    start 63, size 4225473 (2063 MB), flag 0x0
        beg: cylinder    0, head   1, sector  1
        end: cylinder  523, head 127, sector 63

Now it's time to create the disklabel for the NetBSD partition. The correct steps to do this are:

# disklabel sd0 > tempfile
# vi tempfile
# disklabel -R -r sd0 tempfile

If you try to create the disklabel directly with

# disklabel -e sd0

you get the following message

disklabel: ioctl DIOCWDINFO: No disk label on disk;
use "disklabel -I" to install initial label

because the disklabel does not yet exist on the disk.

Now we create some disklabel partitions, editing the tempfile as already explained. The result is:

#      size   offset   fstype [fsize bsize   cpg]
a:  2048004       63   4.2BSD   1024  8192    16 # (Cyl.  0*- 3969*)
c:  4226662       63   unused      0     0       # (Cyl.  0*- 8191*)
d:  4226725        0   unused      0     0       # (Cyl.  0 - 8191*)
e:  2178658  2048067   4.2BSD   1024  8192    16 # (Cyl.  3969*- 8191*)

Note: When the disklabel has been created it is possible to optimize it studying the output of the command newfs -N /dev/rsd0a, which warns about the existence of unallocated sectors at the end of a disklabel partition. The values reported by newfs can be used to adjust the sizes of the partitions with an iterative process.

The final operation is the creation of the file systems for the newly defined partitions (a: and e:).

# newfs /dev/rsd0a
# newfs /dev/rsd0e

The disk is now ready for usage, and the two partitions can be mounted. For example:

# mount /dev/sd0a /mnt

If this succeeds, you may want to put an entry for the partition into /etc/fstab.

How to rebuild the devices in /dev

First shutdown to single user, partitions still mounted rw (read-write); You can do that by just typing shutdown now while you are in multi user mode, or reboot with the -s option and make / and /dev read-writable by doing.

# mount -u /
# mount -u /dev


# mkdir /newdev
# cd /newdev
# cp /dev/MAKEDEV* .
# sh ./MAKEDEV all
# cd /
# mv dev olddev
# mv newdev dev
# rm -r olddev

Or if you fetched all the sources in /usr/src:

# mkdir /newdev
# cd /newdev
# cp /usr/src/etc/MAKEDEV.local .
# ( cd /usr/src/etc ; make MAKEDEV )
# cp /usr/src/etc/obj*/MAKEDEV .
# sh ./MAKEDEV all
# cd /
# mv dev olddev; mv newdev dev
# rm -r olddev

You can determine $arch by

# uname -m


# sysctl hw.machine_arch
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