Difference between revisions of "Xen Dom0"

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So before anything else verify that you can '''reliably''' log into your Alpine box through [[Setting_up_a_ssh-server|SSH]], because with some video chipset (intel in my case) xen will blank your screen so you will have to use SSH.
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This guide will show you how to perform a Xen Dom0 install on a HDD, so you can have your Dom0. The first step is to perform a normal HDD install of Alpine Linux, which can be accomplished following the guide [[Install to disk]]. Once the install is finished, and you have rebooted into your new system, it's time to install the Xen packages:
  
Then upgrade your setup to [[Upgrading_to_Edge|Edge/testing]] (as of the date of writing, Xen is only available in Edge). Install Xen:
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{{Cmd|apk add xen}}
  
{{Cmd|apk add xen}}
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This will install Xen Hypervisor and Tools (both xl and xend) and all the required packages. The next step is to modify your extlinux.cfg and add an entry to boot Xen:
  
Modify your extlinux.cfg (credits: http://lists.alpinelinux.org/alpine-devel/1406.html)
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Normal boot:
since video card is not working for now, we will use a serial console:
 
  
 
<pre>
 
<pre>
SERIAL 0 115200
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LABEL xen
DEFAULT menu.c32
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  KERNEL /boot/mboot.c32
PROMPT 0
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  APPEND /boot/xen.gz --- /boot/grsec root=UUID=<YOUR-DISK-UUID> modules=ext4 --- /boot/grsec.gz
MENU TITLE Alpine/Linux Boot Menu
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</pre>
MENU HIDDEN
 
MENU AUTOBOOT Alpine will be booted automatically in # seconds.
 
TIMEOUT 50
 
  
LABEL 0
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Serial console boot:
  MENU LABEL XEN
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<pre>
   KERNEL mboot.c32
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LABEL xen
   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
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   KERNEL /boot/mboot.c32
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   APPEND /boot/xen.gz com1=115200,8n1 console=com1 --- /boot/grsec root=UUID=<YOUR-DISK-UUID> modules=ext4 --- /boot/grsec.gz
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</pre>
  
LABEL 1
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{{Note|<nowiki>remember to change <YOUR-DISK-UUID> with the UUID of your boot disk (you can copy it from the normal Alpine Linux boot entry)</nowiki>}}
  MENU LABEL Linux
 
  KERNEL grsec
 
  APPEND initrd=grsec.gz root=UUID=f40e340b-ea49-445b-81c0-4d7104b56662 modules=ext4
 
  
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It's also a good idea to check [http://wiki.xen.org/wiki/Xen_Hypervisor_Boot_Options Xen Boot options] and set dom0_mem, dom0_vcpus_pin and dom0_max_vcpus at least.
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The next step is to load the necessary kernel modules for Xen, we will add them to /etc/modules, so they will be loaded automatically on boot:
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<pre>
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# echo "xen_netback" >> /etc/modules
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# echo "xen_blkback" >> /etc/modules
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# echo "tun" >> /etc/modules
 
</pre>
 
</pre>
Of course adapt this accordingly to your setup (UUID, modules, etc).
 
  
Let's start Xen services:
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The last step is to configure startup services, we will need udev and xencommons at least to be started on boot:
{{Cmd|
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apk add xen
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<pre>
apk add udev
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# rc-update add udev sysinit
rc-service udev start ; rc-service udev-postmount start
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# rc-update add udev-postmount
rc-service xencommons start
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# rc-update add xencommons
}}
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</pre>
xl should work. If you want "xm" command
 
{{Cmd|rc-service xend start}}
 
  
So let's install services at boot time :
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If you need the xm toolstack, also add xend to startup services:
{{Cmd|
 
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:
 
 
<pre>
 
<pre>
# Put a getty on the serial port
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# rc-update add xend
#ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt100
 
hvc0::respawn:/sbin/getty -L hvc0 115200 vt100
 
 
</pre>
 
</pre>
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:
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Ok, now you have a fully functional Xen install, it's time to boot into it.
{{Cmd|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 (!):
 
{{Cmd|
 
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)
 
{{Cmd|
 
ifconfig eth0 0.0.0.0
 
brctl addif xenbr0 eth0
 
ifconfig xenbr0 192.168.1.10
 
}}
 
  
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<pre>
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# reboot
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</pre>
  
on going debug:
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Also remember to configure at least one network bridge following the [[Howto_Configure_a_Network_Bridge]] guide.
vi /etc/rc.conf
 
rc_sys="xen0"
 
why ?
 
  
 
== See also ==
 
== See also ==

Revision as of 11:46, 25 June 2012

This guide will show you how to perform a Xen Dom0 install on a HDD, so you can have your Dom0. The first step is to perform a normal HDD install of Alpine Linux, which can be accomplished following the guide Install to disk. Once the install is finished, and you have rebooted into your new system, it's time to install the Xen packages:

apk add xen

This will install Xen Hypervisor and Tools (both xl and xend) and all the required packages. The next step is to modify your extlinux.cfg and add an entry to boot Xen:

Normal boot:

LABEL xen
  KERNEL /boot/mboot.c32
  APPEND /boot/xen.gz --- /boot/grsec root=UUID=<YOUR-DISK-UUID> modules=ext4 --- /boot/grsec.gz

Serial console boot:

LABEL xen
  KERNEL /boot/mboot.c32
  APPEND /boot/xen.gz com1=115200,8n1 console=com1 --- /boot/grsec root=UUID=<YOUR-DISK-UUID> modules=ext4  --- /boot/grsec.gz
Note: remember to change <YOUR-DISK-UUID> with the UUID of your boot disk (you can copy it from the normal Alpine Linux boot entry)

It's also a good idea to check Xen Boot options and set dom0_mem, dom0_vcpus_pin and dom0_max_vcpus at least.

The next step is to load the necessary kernel modules for Xen, we will add them to /etc/modules, so they will be loaded automatically on boot:

# echo "xen_netback" >> /etc/modules
# echo "xen_blkback" >> /etc/modules
# echo "tun" >> /etc/modules

The last step is to configure startup services, we will need udev and xencommons at least to be started on boot:

# rc-update add udev sysinit
# rc-update add udev-postmount
# rc-update add xencommons

If you need the xm toolstack, also add xend to startup services:

# rc-update add xend

Ok, now you have a fully functional Xen install, it's time to boot into it.

# reboot

Also remember to configure at least one network bridge following the Howto_Configure_a_Network_Bridge guide.

See also