From domU read the xenstore (ec2, linode etc)

In case you wonder what is the dom0 running for your instance/vps this will give you information from xenstore. Taken from a FreeBSD receipe and adapted to linux.

Building & installation
-----------------------

Prerequisites: make, XENHVM or XEN kernel (GENERIC will not work) - all this is already there if you run as pv.

1. wget http://bits.xensource.com/oss-xen/release/4.1.1/xen-4.1.1.tar.gz

2. tar xvfz xen-4.1.1.tar.gz

3. cd xen-4.1.1/tools

4. make -C include

5. cd misc

6. make xen-detect

7. install xen-detect /usr/local/bin

8. cd ../xenstore

9. Build client library and programs:
  make clients

10. Install client library and programs:
  install libxenstore.so.3.0 /usr/local/lib
  install xenstore xenstore-control /usr/local/bin
  cd /usr/local/bin
  ln xenstore xenstore-chmod
  ln xenstore xenstore-exists
  ln xenstore xenstore-list
  ln xenstore xenstore-ls
  ln xenstore xenstore-read
  ln xenstore xenstore-rm
  ln xenstore xenstore-write

(in case that your ld loader doesn't look into /usr/local/lib do this
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib)


Usage
-----

1. Set required environment variable:
  export XENSTORED_PATH=/dev/xen/xenstore -- FreeBSD
  export XENSTORED_PATH=/proc/xen/xenbus -- Linux

2. Now you can do things such as:
  xen-detect
  xenstore-ls device
  xenstore-ls -f /local/domain/0/backend/vif/11/0
  xenstore-read name

Xen resize disk (image) into DomU

The objective is to increase the storage allocated to a xen DomU vm.
Let's say the situation before we do anything looks like this:

The virtual machine name (as seen into xm list)  rhel-5.3-HARMONY
The vm is using tapio disk image files (not lvm) for the hard drive.

root@localhost.localdomain[~]11:12:00# df -k

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/xvda 9048256 3198968 5481516 37% /
tmpfs 1048576 0 1048576 0% /dev/shm

I want to add an extra 1GB space to this the 9GB already in there (the red label above).

Steps to do this:

• Shutdown the virtual machine (vm) - xm shutdown rhel-5.3-HARMONY
• Make a backup of the disk  - cp rhel-5.3-HARMONY.img rhel-5.3-HARMONY.img.backup
• Create an empty file with the desired size (I choosed 1GB) - dd if=/dev/zero of=ZeroContentFile bs=1024 count=1000000
• Append the new empty file to the initial image file - cat ZeroContentFile >> rhel-5.3-HARMONY.img -  before we did the append on the filesystem (doing ls -al):

          -rwxr-xr-x 1 root root 9414967296 May 3 11:19 rhel-5.3-HARMONY.img
          and after:
          -rwxr-xr-x 1 root root 10438967296 May 3 11:24 rhel-5.3-HARMONY.img

• Delete the temporary empty file - rm ZeroContentFile
• Resize the image file - resize2fs -f rhel-5.3-HARMONY.img
• Check with fsck the file - fsck.ext3 rhel-5.3-HARMONY.img
• Start the vm to see if the new disk has been added - xm create /etc/xen/rhel-5.3-HARMONY.cfg
• Check the disk space and you will see

root@localhost.localdomain[~]11:31:48# df -k
Filesystem 1K-blocks Used Available Use% Mounted on

/dev/xvda 10033864 3198928 6529108 33% /
tmpfs 1048576 0 1048576 0% /dev/shm


That's it you just increased your space by 1GB for the vm.
One thing to keep in mind is to do the backup of the original disk (just in case something goes wrong).

Build xen templates images with yum and rpm

Great example

http://www.virtuatopia.com/index.php/Building_a_Xen_Guest_Root_Filesystem_using_yum_and_rpm

Create from scratch a Xen image [Part-1]

This is a mini howto on creating from scratch a xen domU guest system cloning the
hostOS.

What you need:

- have a host os which runs xen in dom0 (you can install a centOS and choose virtualization as profile)
- some disk space (i put 20Gb for the / and 2 for swap)
- run the following two commands to set the volumes

pvcreate /dev/sda7 -- change the /dev/sda7 with whatever you want to
vgcreate VolGroup00 /dev/sda7 -- change the /dev/sda7 with whatever you want to

if unsure what to do look it on on how to create volumes in linux (google it ... )



The following script will create you and image:

#!/bin/sh

##########################################
echo $0 "Starting"                       #
echo "This script will clone the guestOS #
creating a new xen image"                #
#
# echo "Author: dioda11@gmail.com"       #
##########################################

if [ $@ ne 1 ]; then
echo "please give a numeric identifier for the clone
between 10 and 100"
exit 1;
# if ![ $1 lt 100 ]  
fi

IMGID=$1
BASEDIRMOUNT=/mnt

VOLGROUP=VolGroup00

lvcreate  -L 20G -n   LV_VM$IMGID_RH5.3_ROOT   $VOLGROUP
lvcreate  -L 2G -n   LV_VM$IMGID_RH5.3_SWAP  $VOLGROUP

mkfs.ext3  /dev/$VOLGROUP/LV_VM$IMGID_RH5.3_ROOT
mkswap  /dev/$VOLGROUP/LV_VM$IMGID_RH5.3_SWAP


if [ -d $BASEDIRMOUNT/$IMGID ]; then
mount /dev/$VOLGROUP/LV_VM$IMGID_RH5.3_ROOT $BASEDIRMOUNT/$IMGID
echo "Mounting the /dev/$VOLGROUP/LV_VM$IMGID_RH5.3_ROOT was " $? 
else
mkdir -p $BASEDIRMOUNT/$IMGID
echo "Creating $BASEDIRMOUNT/$IMGID was  " $?
mount /dev/$VOLGROUP/LV_VM$IMGID_RH5.3_ROOT $BASEDIRMOUNT/$IMGID
echo "Mounting the /dev/$VOLGROUP/LV_VM$IMGID_RH5.3_ROOT was " $? 
fi


echo "Cloning the host OS === "

ARCH=`uname -m`

if [ $ARCH == "x86_64" ]; then 
cp -ax /{bin,dev,etc,lib,lib64,root,sbin,usr,var} $BASEDIRMOUNT/$IMGID
else 
cp -ax /{bin,dev,etc,lib,root,sbin,usr,var} $BASEDIRMOUNT/$IMGID
fi

mkdir $BASEDIRMOUNT/$IMGID/{home,proc,opt,sys,tmp}
chmod 777 $BASEDIRMOUNT/$IMGID/tmp

echo "Cloning finished === " $?


echo "At this point you need to fix the /etc/fstab and create the xen config file"

# umount $BASEDIRMOUNT/$IMGID

------------------------

Xen install via CFengine on linux CentOS5.0

Objective:

Have a linux host with the xen kernel on CentOS5.0
The hosts OS has 5 machines inside that run CentOS 4.4 with different applications.