Creating OpenVZ LiveCD based on Centos 4.4
This article is a step by step guide explaining how to add OpenVZ functionality to Centos 4.4 LiveCD. As a result, you will have a LiveCD, that can boot in various OpenVZ kernels (rhel4-2.6.9, 2.6.18, rhel5-2.6.18, 2.6.20) and in original CentOS kernel also. After booting from CD, you will be able to create VEs, start them, enter them - i.e. perform common OpenVZ activity.
CentOS 5 LiveCD is already announced and as soon as it will be available we'll update the article.
Contents
General actions
It is quite easy to add OpenVZ functionality to existent LiveCD. The most difficult work is already done by the original LiveCD creators. But it requires pretty much hand job. Probably some day some good guy will automatize this process. ;)
Actually you need to know the following general actions: everything else is only technical details.
- Get a copy of CentOS 4.4 LiveCD iso image
- Add squashfs support to your kernel (TODO: use unsquashfs instead)
- Extract the contents of *.mo files from CD using squashfs and construct LiveCD root filesystem.
- Compile OpenVZ kernels with squashfs and unionfs support
- Get OpenVZ user-space tools: vzctl, vzquota, vzpkg, ... and some precreated templates.
- Install OpenVZ kernel, tools and templates in LiveCD root filesystem
- Remove some packages from LiveCD root filesystem
- Modify initrd image: add there kernel modules for OpenVZ kernels
- Introduce some small changes to isolinux configuration file
- Create new iso image
Technical details
This part contents detailed description of LiveCD creation. I've removed the output of some commands in order to simplify the reading.
Creating booted LiveCD root filesystem
Create a directory, that will be our "workbench":
# cd ~ # mkdir workbench # cd workbench
First of all we need some raw material - CentOS 4.4 LiveCD:
# wget http://mirror.nsc.liu.se/CentOS/4.4/isos/i386/CentOS-4.4-i386-LiveCD.iso # wget http://mirror.nsc.liu.se/CentOS/4.4/isos/i386/md5sum.livecd # md5sum --check md5sum.livecd CentOS-4.4-i386-LiveCD.iso: OK
Copy the contents of CD to the directory, where we will form the OpenVZ LiveCD filesystem. I named this directory "ovz-livecd":
# mkdir ovz-livecd # mkdir mount # mount -o loop -t iso9660 CentOS-4.4-i386-LiveCD.iso mount/ # cp -a mount/* ovz-livecd/ # umount mount # rm -rf mount
You can see, that ovz-livecd/base/ directory owns several *.mo files - images of squashfs filesystem, and each image holds one directory of LiveCD root filesystem: bin, usr and so on:
# ls -1 ovz-livecd/base bin.mo etc.mo lib.mo root.mo sbin.mo usr.mo var.mo
In order to decompress these images we need squashfs tools. The source archive of squashfs contents patch for the kernel (to be able mount squashfs), and user-space tools for compressing/decomprassing usual filesytem into squashfs filesystem. Well, we don't need the kernel patch right now (but we will need it later), we only want to install squashfs user-space tools:
# wget wget http://switch.dl.sourceforge.net/sourceforge/squashfs/squashfs3.2-r2.tar.gz # tar xzf squashfs3.2-r2.tar.gz # cd squashfs3.2-r2/squashfs-tools/ # make cc mksquashfs.o read_fs.o sort.o -lz -lpthread -lm -o mksquashfs cc unsquashfs.o -lz -o unsquashfs # cp mksquashfs /usr/bin/ # cp unsquashfs /usr/bin/ # cd ~/workbench
Well, having the intruments in hand, why not extract the images? Create a directory, called livecd-root, that will store the root filesystem for booted LiveCD. I.e. it will content /bin, /sbin, /etc and other directories, which you will see after booting the LiveCD. Unfortunately unsquashfs tool is not very convenient, and I found only this way to use it:
# mkdir livecd-root # unsquashfs ovz-livecd/base/bin.mo # mv squashfs-root/bin/ livecd-root/ # rm -rf squashfs-root # unsquashfs ovz-livecd/base/etc.mo # mv squashfs-root/etc/ livecd-root/ # rm -rf squashfs-root # unsquashfs ovz-livecd/base/lib.mo # mv squashfs-root/lib/ livecd-root/ # rm -rf squashfs-root # unsquashfs ovz-livecd/base/root.mo # mv squashfs-root/root/ livecd-root/ # rm -rf squashfs-root # unsquashfs ovz-livecd/base/sbin.mo # mv squashfs-root/sbin/ livecd-root/ # rm -rf squashfs-root # unsquashfs ovz-livecd/base/usr.mo # this action takes some time, be patient ;) # mv squashfs-root/usr/ livecd-root/ # rm -rf squashfs-root # unsquashfs ovz-livecd/base/var.mo # mv squashfs-root/var/ livecd-root/ # rm -rf squashfs-root
Yet we have nearly complete root filesystem of booted LiveCD in livecd-root directory. However some things are missing, and I guess you know what are they: /dev, /proc, /sys, /tmp and /boot directories. We need them, because some tools (rpm, bash,...) will not work without them in chrooted environment later.
# mkdir root/dev # cp -a /dev/* root/dev # mkdir root/proc # mount -t proc proc root/proc/ # mkdir root/sys # mount -t sysfs sysfs root/sys/ # mkdir root/tmp # mkdir root/boot
That's it. We have booted LiveCD root filesystem in livecd-root directory. Now we can chroot in this directory and install all needed packages. But what packages do we need?
- OpenVZ kernel
- OpenVZ tools: vzctl, vzquota, vzpkg, vzrpm43, vzrpm44, vzyum
- OpenVZ template metadatas: centos-4, fc-3, fc4 and fc-5
- Some OpenVZ precreated templates
- Some CentOS tools updates: sqlite package
Tools and templates related packages can be simply downloaded and installed. But it is not so easy with kernel. Usual OpenVZ kernel won't work: it doesn't support squashfs. The next chapter explains how to create RPM package with OpenVZ kernel, that supports squashfs
Building OpenVZ kernels and kernel modules
To be continued...
Obrezki
TODO rpms/ rpms/kernel rpms/tools rpms/update
Uninstall lsctp-tools package, because these tools they need kernel version prior to 2.6.10:
rpm -e lksctp-tools-1.0.2-6.4E.1.i386
Uninstall kernel-module-xfs package, because these modules are compiled against original
rpm -e kernel-module-xfs-2.6.9-42.livecd.c4-0.1-3.i686
cd /tmp/rpms/kernel rpm -ivh kernel-smp-2.6.18-ovz028stab033.1.i686.rpm rpm -e kernel-2.6.9-42.livecd.c4
cd /tmp/rpms/updates rpm -Uvh sqlite-3.3.6-2.i386.rpm
- rpm -ivh vz*
Preparing... ########################################### [100%]
1:vzrpm44 ########################################### [ 8%] 2:vzrpm44-python ########################################### [ 15%] 3:vzrpm43-python ########################################### [ 23%] 4:vzrpm43 ########################################### [ 31%] 5:vzyum ########################################### [ 38%] 6:vzquota ########################################### [ 46%] 7:vzctl-lib ########################################### [ 54%] 8:vzctl ########################################### [ 62%] 9:vzpkg ########################################### [ 69%] 10:vztmpl-centos-4 ########################################### [ 77%] 11:vztmpl-fedora-core-3 ########################################### [ 85%] 12:vztmpl-fedora-core-4 ########################################### [ 92%] 13:vztmpl-fedora-core-5 ########################################### [100%]
