Xen Dom0

So before anything else verify that you can reliably log into your Alpine box through SSH, because with some video chipset (intel in my case) xen will blank your screen so you will have to use SSH.

Then upgrade your setup to Edge/testing (as of the date of writing, Xen is only available in Edge). Install Xen:

apk add xen

Modify your extlinux.cfg (credits: http://lists.alpinelinux.org/alpine-devel/1406.html) since video card is not working for now, we will use a serial console:

SERIAL 0 115200 
DEFAULT menu.c32
PROMPT 0
MENU TITLE Alpine/Linux Boot Menu
MENU HIDDEN
MENU AUTOBOOT Alpine will be booted automatically in # seconds.
TIMEOUT 50

LABEL 0
  MENU LABEL XEN
  KERNEL mboot.c32
  APPEND /boot/xen-4.gz iommu=1 dom0_mem=1024M dom0_max_vcpus=2 dom0_vcpus_pin  loglvl=all guest_loglvl=all com1=115200,8n1 console=com1  --- /boot/grsec root=UUID=f40e340b-ea49-445b-81c0-4d7104b56662 modules=ext4 console=hvc0 earlyprintk=xen nomodeset --- /boot/grsec.gz

LABEL 1
  MENU LABEL Linux
  KERNEL grsec
  APPEND initrd=grsec.gz root=UUID=f40e340b-ea49-445b-81c0-4d7104b56662 modules=ext4

Of course adapt this accordingly to your setup (UUID, modules, etc).

Let's start Xen services:

apk add xen apk add udev rc-service udev start ; rc-service udev-postmount start rc-service xencommons start

xl should work. If you want "xm" command

rc-service xend start

So let's install services at boot time :

rc-update add udev sysinit rc-update add udev-postmount default rc-update add xencommons rc-update add xend

since we use a serial line, let'a add a serial console prompt, modify your /etc/inittab accordinly:

# Put a getty on the serial port
#ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt100
hvc0::respawn:/sbin/getty -L hvc0 115200 vt100

hvc0 is Xen console output, where we have already redirected the kernel messages. To switch to Xen console, type three time "Ctrl+a"

Now you can configure your guest, but before don't forget to load Xen kernel module:

modprobe xen-gntdev modprobe xen-gntalloc modprobe tun echo "xen-gntdev" >> /etc/modules echo "xen-gntalloc" >> /etc/modules echo "tun" >> /etc/modules

Yes, tun is not a Xen module but is needed to create tap interface in Dom0. Before creating your VM don't forget to create xenbr0 bridge, otherwise Xen will change eth0 into peth0 and eth0 will become a bridge (!):

brctl addbr xenbr0 ifconfig xenbr0 up

So now if you want to plug your "real" network card in your bridge: (192.168.1.10 is eth0 ip)

ifconfig eth0 0.0.0.0 brctl addif xenbr0 eth0 ifconfig xenbr0 192.168.1.10

on going debug: vi /etc/rc.conf rc_sys="xen0" why ?

See also

• Xen Dom0 on USB or SD