NetBSD as a DomU

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c33ris2's gentle guide to installing NetBSD in a prgmr DomU (January 2009)

Note: By June 2010 (or earlier) some of the dom0 hosts have packed the installer files into the /distros collection available to many recovery images. In these cases, the fetching activity is no longer required.

Note: for mantle/chessboard users: Mantle is currently running Xen 4.0.1. There is a bug in NetBSD that breaks networking when running in a Xen4 domU.

Note: what Xen version is marshall? It also has the issue.

Note: A -current NetBSD kernel is required to run under Xen 4.x. When NetBSD 6 is released, these notes will go away. -current is for EXPERTS ONLY.

Note: Daily binary kernels (and bootable installers) with Xen 4.x compatibility are available at and later.

Note: It seems that loadable kernel modules are not supported under Xen. See Among other things, this renders pf firewalling unusable under the default NetBSD kernel, as loading the pf module (modload /usr/lkm/pf.o) will cause the kernel to crash; building a new kernel with pf built-in may work.

Getting Started

Installing NetBSD as DomU is easy, but not trivial.

Boot your preconfigured system, in order to discover, and note for later use, YOUR_IP, NETMASK, GATEWAY, and NAMESERVER as follows:

Run 'ifconfig eth0' and note your "inet addr" and "Mask" values.
Run 'route' or 'ip route' and note the IP of the default gateway.
Run 'cat /etc/resolv.conf' and note the IP of the nameserver

From the control menu on your dom0 host, destroy/shutdown the instance, and restart ("create/start") it, selecting the "rescue" option from the bootloader. Login as 'root'.

Your fixed disk, as known to the linux rescue image, is /dev/xvda. Later, when booted to the NetBSD installer, it is identified as /dev/xbd0.

For NetBSD, this disk must be partitioned, and the NetBSD installer files placed therein.

fdisk /dev/xvda

From within fdisk,

  • delete the existing partition, *which will destroy your current OS image and data*
  • create a new primary partition #1, with first cylinder at default=1 and last cylinder at +32M
  • create a new primary partition #2, directly after partition 1 and last cylinder at end of disk
  • change the ID of the new partition #2 to 'a9' (NetBSD)
  • write the new parition table to the disk.
  • exit fdisk

Success to this point is evidenced by the prseence of /dev/xvda1 which must now be formatted, mounted, and a /boot directory created:

mkfs.ext2 /dev/xvda1
mount -n /dev/xvda1 /mnt
mkdir /mnt/boot
mkdir /mnt/boot/grub

If the file 'netbsd64.tar.gz' exists in /distros, skip over to #Unpacking the Installer

Note: if you will be using a -current install, then don't bother with /distros

Otherwise you'll have to proceed here with

Fetching the Installer

Substituting actual values observed (above) for YOUR_IP, NETMASK, GATEWAY, and NAMESERVER ...

ifconfig eth0 up YOUR_IP/NETMASK
route add default gw GATEWAY eth0
echo "nameserver NAMESERVER" >/etc/resolv.conf

wget and extract to /mnt/boot/ :

cd /mnt/boot
gunzip netbsd-INSTALL_XEN3_DOMU.gz
gunzip netbsd-XEN3_DOMU.gz

Note: if you will be using -current, you must get a current build from NetBSD's releng. ( Check for a successful amd64 build in the log data, then determine the corresponding location in the binary snapshots.

Configuring Boot Menu

Create a file boot/grub/menu.lst with this content:

timeout 5

title NetBSD run
        root (hd0,0)
        kernel --type=netbsd /boot/netbsd-XEN3_DOMU

title NetBSD install
        root (hd0,0)
        kernel --type=netbsd /boot/netbsd-INSTALL_XEN3_DOMU

Skip to #Booting the Installer

Unpacking the Installer

This section presumes the presence, in the rescue instance, of /distros/netbsd64.tar.gz
Unpack this into the new boot menu, and shutdown.

tar zxf /distros/netbsd64.tar.gz -C /mnt/boot/
shutdown -h now

NOTE This step isn't necessary if you perform a network install

Booting the Installer

Returning to the control menu on your dom0 host, change your bootloader selection to 'amd64' instead of 'i386'. Destroy/shutdown your instance if it is running, and create/start it again, this time selecting first the "user bootloader configuration" from the options presented by the dom0, and after that select the installer from your new user bootloader. This should take you to the NetBSD Installer, for which a tutorial exists at

Install onto xbd0

When presented with the option, choose
b: Use existing partition sizes
The next screen should show the existing BSD-disklabel partitions, as follows for a 3G allocation.

    Start  MB   End  MB  Size  MB FS type    Newfs Mount Mount point
    --------- --------- --------- ---------- ----- ----- -----------
 a:         0         0         0 unused
 b:         0         0         0 unused
 c:         0      3071      3072 NetBSD partition
 d:         0      3071      3072 Whole disk
 e:         0        29        30 Linux Ext2
 f:         30     3071      3041 4.2BSD     Yes   Yes   /
 g:         0         0         0 unused

If you're new to NetBSD partitioning, which I am, which is why I'm writing this, refer to this NetBSD Guide section

In order to install NetBSD properly, lets move the root partition to label:a and create swap. Select a:, set the partition type to "FFSv2" instead of "unused", and use 'e' as the start of your partition. Leave space at the end for swap. I used 128 MB, but you may want more depending on your application and VM allocation. Make sure to set Newfs, Mount, and Mount point correctly. Select b: and create swap until the end of the disk (-1).

You can also set the mount point for e:.

Finally, remove (the now obsolete) label:f by setting it to unused.

Here is an example disklabel setup for a 3072M disk with a 30M boot partition:

    Start  MB   End  MB  Size  MB FS type    Newfs Mount Mount point
    --------- --------- --------- ---------- ----- ----- -----------
 a:        30      2942      2912 FFSv2      Yes   Yes   /
 b:      2943      3071       128 swap
 c:         0      3071      3072 NetBSD partition
 d:         0      3071      3072 Whole disk
 e:         0        29        30 Linux Ext2       Yes   /boot
 f:         0         0         0 unused

Select "accept these sizes" and continue with the installation.

When prompted by the installer, select "use existing bootblocks".

Install by FTP

When prompted by the installer, use the xennet0 device and when it asks for "Network media type" just press enter.

Try to use DHCP. If it doesn't work, Use the actual values observed (above) for
when prompted by the installer

The installation of NetBSD is now complete.  The system should boot
from hard disk.  Follow the instructions in the INSTALL document about final
configuration of your system.  The afterboot(8) manpage is another
recommended reading; it contains a list of things to be checked after the
first complete boot.

At a minimum, you should edit /etc/rc.conf to match your needs.  See
/etc/defaults/rc.conf for the default values.


Mount boot partition in NetBSD domU

Log in as root.

# mkdir /extboot
# vi /etc/fstab

find the line in fstab that contains /dev/xbd0e and make it look like this:

/dev/xbd0e              /extboot        ext2fs    rw               0 0

Now it will be readable:

# mount /extboot
# cd /extboot/boot/
# ls
grub                      netbsd-INSTALL_XEN3_DOMU  netbsd-XEN3_DOMU

NetBSD 6.x

As of December 2012, it has been reported that NetBSD can also be installed following these directions, using these images:

As of September 2013, NetBSD 6.1.1 i386 and AMD64 can be installed successfully, ex.