OpenSolaris Xen domU

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This page describes the installation of the July 2007 update of OpenSolaris on a Xen domU running under a Linux dom0. It has all been written based on my experiences with Debian GNU/Linux 4.0 as the dom0 so some details might not match your system and others might just be wrong. If you have any corrections or additions, please email me here: rupert.hair@ntlworld.com

Contents

Getting the Installation Media

The installer is available as DVD image from Sun's Download Centre here. It is distributed as an ISO file, which has been split into six parts and where each part has been zipped.

I downloaded each file, verified them using the supplied md5sums, and then ran the following from bash to unzip and recombine them:

mkdir /usr/lib/xen-solaris/
for foo in `ls 66-0624-nd-iso-[a-f].zip`; do
    unzip -p $foo;
done >/usr/lib/xen-solaris/66-0624-nd.iso

Extracting the Kernel and Initial ramdisk

To boot OpenSolaris under Xen you need both a kernel and initial ramdisk available on your dom0. The documentation seems to assume that you are running an OpenSolaris dom0 and so will already have a copy of the kernel and ramdisk available. In our case, with a Linux dom0, we will need to extract the kernel and ramdisk from the ISO image like so:

mkdir /mnt/tmp
mount -o loop,ro 66-0624-nd.iso /mnt/tmp
cp /mnt/tmp/boot/x86.miniroot /usr/lib/xen-solaris/x86.miniroot-66-0624-nd
cp /mnt/tmp/boot/platform/i86xpv/kernel/unix /usr/lib/xen-solaris/unix-66-0624-nd
umount /mnt/tmp

Configuring Xen for the Installation

Before you can boot OpenSolaris to begin the installation you will need to create a Xen configuration file defining the virtual disk, virtual DVD drive, kernel, ramdisk, memory size and kernel parameters. Here's an example:

name = 'argolin'
memory = '1024'
disk = [ 'file:/mnt/tmp/66-0624-nd.iso,6:cdrom,r', 'phy:/dev/xenvg/argolin.disk,0,w' ]
vif = [ '' ]
on_shutdown = 'destroy'
on_reboot = 'destroy'
on_crash = 'destroy'
kernel = '/usr/lib/xen-solaris/unix-66-0624-nd'
ramdisk = '/usr/lib/xen-solaris/x86.miniroot-66-0624-nd'
extra = '/platform/i86xpv/kernel/unix - nowin -B install_media=cdrom'

This creates a domU called argolin with 1024MB of RAM, a virtual DVD drive from the image in '/mnt/tmp/66-0624-nd.iso', a virtual disk from the device '/dev/xenvg/argolin.disk', the default virtual network interface and the kernel and ramdisk extracted earlier. This configuration file should be saved in '/etc/xen/' and given a name like 'argolin.conf' but this is up to you.

SMP-related IO Hang (part 1)

My first tries at booting OpenSolaris as a domU resulted in the installer hanging at some point during the main package installation process. After much help from the kind folk of #solaris-xen on irc.oftc.net we found that this was an IO hang which is only seen on SMP systems. A work-around for this bug exists in the kernel but has to be enabled manually using the kernel's built in debugger. The '-kd' kernel parameter, shown below, causes the kernel to open the debugger as soon as possible after boot.

extra = '/platform/i86xpv/kernel/unix -kd - nowin -B install_media=cdrom'

Booting the Installer

Once you have the DVD image, have extracted the kernel and ramdisk, and have created the Xen configuration file you can boot the installer like so:

xm create -c argolin.conf

The last argument to the command is the name of the configuration file created above.

You should then see:

Using config file "/etc/xen/argolin.conf".
Started domain argolin
SunOS Release 5.11 Version xen-nv66-2007-06-24 32-bit
Copyright 1983-2007 Sun Microsystems, Inc.  All rights reserved.
Use is subject to license terms.
WARNING: Found xen v3.0.3-1 but need xen v3.0.4-1-sun
WARNING: The kernel may not function correctly
Configuring /dev
Solaris Interactive Text (Console session)
Using install cd in /dev/dsk/c0d6p0
...
...

The warnings about the Xen version mismatch may be ignored as these apparently only apply to 64bit systems (thanks again #solaris-xen).

SMP-related IO Hang (part 2)

Following a boot with the '-kd' parameter you should see the following:

Using config file "/etc/xen/argolin.conf".
Started domain argolin
Loading kmdb...

Welcome to kmdb
Loaded modules: [ unix krtld genunix ]
[0]> 

You type:

workaround_6557577?W 1

It shows:

workaround_6557577:             0               =       0x1
[0]>

You type:

:c

It shows:

SunOS Release 5.11 Version xen-nv66-2007-06-24 32-bit
Copyright 1983-2007 Sun Microsystems, Inc.  All rights reserved.
Use is subject to license terms.
WARNING: Found xen v3.0.3-1 but need xen v3.0.4-1-sun
WARNING: The kernel may not function correctly
Configuring /dev
...
...

The Installation

Once OpenSolaris has booted the installer will ask you for details of your location and terminal. Make sure you are using a standard 80x25 terminal and select option 6 (PC console). You should then see a shiny, coloured installer. Make sure you say no to the automatic reboot as we need to transfer the kernel and ramdisk to the dom0 after the install.

SMP-related IO Hang (part 3)

You'll be glad to hear that this is the last section dealing with the SMP-related IO hang. To avoid having to use kmdb to enable the workaround during each boot, I added the following line to '/etc/system':

set workaround_6557577 = 1

TCP/UDP Checksum Problem

I also had a problem with the OpenSolaris kernel not generating checksums for TCP and UDP packets. The fix for this is another addition to '/etc/system':

set xnf:xnf_cksum_offload = 0

Finishing up and Rebooting into the Installed System

Unfortunately we need to update the ramdisk after editing '/etc/system' so:

bootadm update-archive -R /a

As mentioned above, we need to make the OpenSolaris kernel and ramdisk available inside the dom0. It is not strictly necessary to transfer the kernel from the domU to the dom0 as it is identical to the installer's kernel but I have shown the scp for both kernel and ramdisk because this may be necessary if the kernel is upgraded at a later point. I chose a full install so that I could use scp to do this but if you have an ftp server handy you should be OK with a more minimal install. At the post-install console I did the following:

/a/usr/bin/scp -S /a/usr/bin/ssh /a/platform/i86xpv/kernel/unix /a/platform/i86pc/boot_archive \
        10.0.0.1:/usr/lib/xen-solaris/

I didn't really know how to shut down the system so I did:

umount /a
shutdown -y -g0 -i0

Once back at your dom0's prompt you need to edit the domU's configuration file to look something like this:

name = 'argolin'
memory = '1024'
disk = [ 'phy:/dev/xenvg/argolin.disk,0,w' ]
vif = [ '' ]
on_shutdown = 'destroy'
on_reboot = 'destroy'
on_crash = 'destroy'
kernel = '/usr/lib/xen-solaris/unix'
ramdisk = '/usr/lib/xen-solaris/boot_archive'
extra = '/platform/i86xpv/kernel/unix'
root = '/dev/dsk/c0d0s0'

Then fire up the domU again and you're away:

xm create -c argolin.conf
Using config file "/etc/xen/argolin.conf".
Started domain argolin
SunOS Release 5.11 Version xen-nv66-2007-06-24 32-bit
Copyright 1983-2007 Sun Microsystems, Inc.  All rights reserved.
Use is subject to license terms.
WARNING: Found xen v3.0.3-1 but need xen v3.0.4-1-sun
WARNING: The kernel may not function correctly
ip: joining multicasts failed (4) on xnf0 - will use link layer broadcasts for multicast
Hostname: argolin.xen.tardis.ed.ac.uk
...
...
argolin.xen.tardis.ed.ac.uk console login:

One final note: I was unable to login to the system as root via ssh by default. I only mention this because most Linux distributions now allow ssh root login by default.