Installing and configuring Xen
Contents
1. Some of the more important properties are e name the domain name which must be unique e g Domain 1 e kernel the full path to the kernel image that is to be used by the domain Typically this would be boot vmlinuz 2 4 27 xenU obviously the version number may be different for the version of the kernel you are using e memory the amount of memory in megabytes to be allocated to the domain e g memory 64 will specify 64 megabytes e ip the kernel ip interface ip 192 168 174 150 address e g e dhcp should the kernel try to obtain an ip address via DHCP i e dhcp dhcp will instruct the kernel to use dhcp and dhcp off will disable dhcp e disk this specifies the disk device s that is are to be made available to the domain As previously explained a domain requires at minimum two disk devices one for the root file system and another as swap space The syntax for this property is where DEV is the name of the physical disk disk phy DEV VDEV MODE device e g dev sdc2 VDEV is the name with which DEV is exported to the domain e g sdal and MODE can be one of w for read write and r for read only So if we have allocated dev sdc2 which has a RedHat installation on it for use by the domain as a root file system and dev sdc3 as the swap space then the specification would read disk phy dev sdc2 sdal w2. phy dev sdc3 sda2 w e root this specifies which device is to be mounted as root This is specified according to the VDEV name given to the disk option In other words we don t specify the root device according to the physical device name e g dev sdc2 but rather according to whatever alias we gave to the physical device name when setting the disk property e g sdal For example root dev sdal ro A final important point that needs to be made is regarding the file etc fstab on the root device for the created domain This file holds information regarding the file systems and it is used for specifying which file systems should be mounted when the system is booted there are other uses as well but those are of no relevance here As explained when setting the disk property VDEV is the name with which the disk is exported to the domain Thus the domain s fstab file must be edited accordingly to reflect the VDEV names and not the actual device names For the example given above fstab would include the following dev sdal ext3 defaults 11 dev sda2 swap swap defaults 0 0 The problem however is that if fstab is not correctly edited the domain will not be able to boot One way to solve this problem is to mount the file system that is to be used by the domain as and editing fstab before creating the domain It should be n
3. The final step is to move our new kernel file and system map to the appropriate directory boot which will ensure that no changes are required to our bootloader configuration boot grub grub conf The following is the exact procedure that needs to be followed note the use of ARCH xen before each Makefile target to specify the architecture for which we are re building the kernel First change to the Linux kernel directory It is prudent to create a backup of your configuration file before creating the new one cd usr src linux 2 4 27 xen0 cp config config BACKUP Note that the configuration file has a filename starting with As such it will only appear in a directory listing obtained with 1s a Invoke the Make target menuconfig to create the new kernel configuration file ARCH xen make menuconfig Select this press return port RAID and LVM a Fn Oct 29 leg root localhost ust sre inux 2 4 27 xen0 ogical volume manager LVM support Activate LVM support Fil Oct 29 a 9 10 54 ES rootelocalhost usr src linux 2 4 27 xeno Create dependencies ARCH xen make dep Build the new kernel may take a while ARCH xen make bzImage Build any modules ARCH xen make modules Install the modules to their correct locations ARCH xen make modules install Finally move the new kernel file and system m
4. install targets ms cd mnt hgfs shared folder cp Twisted 1 3 0 tar gz home marios cd home marios tar xzvf Twisted 1 3 0 tar gz cd Twisted 1 3 0 python setup py build python setup py install xen 2 0 3 install tgz Again copy the file to your home directory and expand the archive An included bash script is then used to complete the installation cd mnt hgfs shared folder cp xen 2 0 3 install tgz home marios cd home marios tar xvf xen 2 0 3 install tgz cd xen 2 0 install sh install sh 1 7 Editing the grub conf file The grub conf file controls and provides the bootup options available in the Red Hat splash screen The following modification of the grub conf file will allow the user the ability to run the VM as both a normal Red Hat 9 machine or as a Xen XenoLinux machine depending on the option chosen in the splash screen When further hard disks are added to the VM they can also be added to the grub conf file allowing the user to freely chose which of the hard disks to boot into The items in bold must be added to the grub conf file in boot grub as follows Sample grub conf gt grub conf generated by anaconda Note that you do not have to rerun grub after making changes to this file NOTICE You have a boot partition This means that all kernel and initrd paths are relative to boot e g root hd0 0 kernel vmlinuz version ro
5. kernel boot vmlinuz 2 4 27 xenU memory 32 disk phy dev sdb2 sdal w disk phy dev sdb3 sda2 pw ip 192 155 144 111 root dev sdal ro dhcp off 2 4 Domain Consoles Once you have successfully booted a domain the command xm list will produce a listing of currently active domains complete with information about each Supplying the 1 flag will produce a longer output which includes the SXP specification for each domain The output produced without 1 has the following format xen01 Name Id Mem MB CPU State Time s Console Domain 0 0 123 0 r 4862 4 Domain 1 10 63 0 b 74 0 9610 e Name the descriptive name given to the domain when it was created e Jd the domain Id within which the virtual machine is running e Mem MB the memory allocated to the domain e CPU the CPU on which this domain is running e State the current domain state r running b blocked p paused s shutdown c crashed e Time s the time in seconds that this domain has had access to the CPU for e Console the TCP port which is accepting connections to the domain console To obtain a domain console the command xm console domain_name is used The domain can be referenced either by its name or by the domain id If the c flag is used with the xm create command a console will be opened for you automatically and you can observe
6. Es gue Servers O Network Servers Di Network Servers ie Home Folder Run Program 43 Run Program XS Run Program D Network Servers Search for Files QJ Search for Files Q search for Files D Open Recent Open Recent 5 Open Recent S Run Program Cj Search for Files Lock Screen 8 Lock Screen tock Screen ED Open Recent gt ff Log Out Log Out Lock Screen Tue Oct 26 M root localhost etc xen DomainCor VNC localhost localdomain 1 root 12 03 I NC localhost localdomain 2 root VNC localhost localdomain 2 root RealVNC in use Domains 0 1 2 and 3 respectively from left to right 3 Storage Management As previously explained a non zero domain needs access to at minimum two disk partitions One of these is to be mounted and used as the root partition and another to be used as the Linux swap space The root partition will need to have a Linux installation placed upon it and as such will typically need to be about 1 to 1 5 Gb in size although this is dependant on the packages that the user chooses to include with the Linux installation The swap space can be any size but again typically around 500 Mb Usually the user is forced to pre empt the number of different partitions that they will require which depends on the number of domains to be created and used and partition their hard disk accordingly A number of approaches can be
7. VolGrp1 lval General Xen amp Linux Resources xen01 The Xen Team Xen User s Manual http www cl cam ac uk Research SRG netos xe n readmes user user html University of Cambridge UK October 2004 xen02 Andresen R J Install and run Xen unstable 2 0 http openlab mu internal web cern ch openlab mu internal Documents Reports Technical Summer 20Students xenhowto pdf August 2004 lin01 Boone K Understanding the Linux boot process http www kevinboone com boot html July 2004 RealVNC vnc01 RealVNC Ltd VNC 4 0 Documentation http www realvnc com documentation html 2004 LVM Ivm01 Robbins D Common Threads Learning Linux LVM Part 1 http www 106 ibm com developerworks linux library l lvm March 2001 Ivm02 Robbins D Common Threads Learning Linux LVM Part 2 http www 106 ibm com developerworks library l Ivm2 html April 2001 lvm03 Tesfamariam M Giles J Implementing Logical Volumes http www dell com downloads global power 4 q03 mic pdf November 2003 Ivm04 Lewis A J LVM HOWTO http www tldp org HOWTO LVM HOWTO October 2004 Ivm05 RedHat LVM2 Resource Page http sources redhat com lvm2 February 2004 13
8. and there is not even the need to reboot your system Furthermore the size of the Volume Group can also be changed so you may decide to add a new PV or you may decide to reduce the VG by removing a PV which you may then go on to assign to another VG for example How do I get it Ivm04 Ivm05 There are currently two versions of LVM LVM 1 0 and LVM 2 0 The former is compatible with 2 4 series kernels and the latter with the 2 6 series kernels On a regular i e unmodified Linux installation 2 4 series kernel the chances are that LVM support is already enabled One way this can be verified is by issuing the command vgscan which scans for active volume groups If you receive the following response vgscan LVM driver module not loaded then LVM is not enabled for your kernel and you will have to go through process of rebuilding the kernel with LVM support enabled see below Otherwise if the response you receive is more like vgscan reading all physical volumes this may take a while vgscan etc lvmtab and etc lvmtab d successfully created vgscan WARNING This program does not do a VGDA backup of your volume group then you can skip the following section and move on to How do I use it How do I install it There are a number of ways in which LVM can be installed to a kernel without LVM support The following
9. is a description of how to install LVMI 0 by rebuilding your kernel An alternative could be to build LVM as a module LKM Loadable Kernel Module and use insmod to insert this into the kernel Furthermore if you are interested in installing LVM2 0 then you should bear in mind that apart from the LVM 2 0 packages you will also need to install the device mapper packages More information for this can be found at Ivm05 To re build the XenoLinux kernel we follow the same procedure as that for re building a regular ie unmodified Linux kernel A 10 Makefile exists within the directory holding Linux source files documentation and kernel files usr src with targets for re building the kernel This process involves first creating a new kernel configuration file usr src linux 2 4 27 xen0 config and setting up any dependencies The new kernel configuration will need to include LVM support Once the target make menuconfig is invoked LVM can be included by selecting Multiple devices driver support and activating this you will then be presented with two more options RAID support and Logical Volume Manager LVM support You should ensure that the latter is activated as part of the kernel and not as a loadable module The new kernel configuration should be saved and following this we need to build the new kernel file create any loadable modules to be used with our new kernel and then install these
10. the domain booting To connect to Domain 1 as it appears above xm console Domain 1 OR xm console 10 To obtain a console immediately after the domain is created xm create cf domlconfig 2 5 REALVNC Whatis it Non zero domains have neither frame buffers or graphics devices since unlike the disks and network devices which are virtualised only Domain 0 has direct access to the display hardware As such an X server can only be run in domain 0 Real VNC Virtual Network Computing is a remote access program available under the GNU General Public Licence vnc01 It can be used to overcome the non availability of the x server on non zero domains since it runs in memory clients can connect to the desktop being served by the vncserver running on a host across a network The program is set up as a client server application with the vncserver running in a non zero domain accepting connections from a vncviewer which runs in domain 0 The vncserver provides a TWM style window manager RealVNC is also fully cross platform so that for instance a vncviewer running on a Windows box can access the desktop served by a vncserver on a Linux box DOMAIN N N gt 0 IP address 192 168 174 111 Install RealVNC 1 Seta password vncpasswd 2 Start the vncserver vncserver amp OR vncserver geometry 640x480 amp 3 Make a note of the display number that the vncserver is using New localhost localdomai
11. Uy invent Installing and configuring Xen Marios Andreou Nimisha Walji Internet Systems and Storage Laboratory HP Laboratories Bristol HPL 2004 207 R 1 February 7 2005 Xen utility We provide a detailed account of the procedures involved in the computing configuration and use of Xen This includes an explanation of the vmware method by which Xen can be installed and run within VMware Virtual virtualisation Machines to provide a flexible and scalable testing environment Consideration is also given to the creation and management of non zero domains with a description of how a graphical desktop may be obtained for these using RealVNC In addition an insight is given into the various approaches that may be adopted with respect to Storage Management focusing on the application of LVM nternal Accession Date Only Approved for External Publication O Copyright Hewlett Packard Company 2004 Acknowledgements We would like to thank Nigel Edwards Chris Dalton and Mike Wray whose contributions have been invaluable in helping to identify resources relevant to the problem domain Contents 1 Using VMware Workstation 4 5 occ cciscoscccasersocsscacsssvaseonndoncenssscadecsouanssonseensaendubsecedswoncsvadussossssecae L 1 1 Creating Virtual Machine etario e eb monte e nu ea pnm 1 1 2 Installing Red Hat Oria 1 1 3 Cloning the Red Hat Virtual Machine annann nnan ne enne enne nee n rennen nnne nnne 1 1 4 Configuring the Network Connec
12. ady networked via VMNetl 1 4 Configuring the Network Connection Changing the ifcfg eth0 file During the Red Hat boot sequence a failure will occur when the system attempts to bring up the interface eth0 this is because the system will try to contact the actual interface card which the VM is not connected to This can be fixed by amending the ifcfg ethO file as follows the items in bold must be added to the file Sample ifcfg eth0 DEVICE eth0 BOOTPROTO dhcp ONBOOT yes check link down return 1 lt Sample ifcfg_eth0 gt The VMs can be assigned IP addresses using the following command and a suitable IP address ifconfig eth0 192 168 xx xx up Once IP addresses have been assigned to both of the VMs the network connection can be checked by launching a ping from one VM and running a tcpdump on the other to check that network traffic is passing between the two 1 5 Installing VMware Tools VMware tools provide some useful extra functionality when using VMware The most important of these features is the Shared Folder capability which allows files to be passed from the host operating system to a Virtual Machine running within VMware and vice versa Shared folders can be set up as follows With the VM running from the VM menu choose the Install VMware tools option This will bring up a window in the VM s Red Hat for mnt cdrom containing a file named vmware linux tools tar gz Once
13. ap to boot You may wish to first create backups of the existing kernel and system map in case there are any problems booting the new kernel cp boot vmlinuz 2 4 27 xen0 boot vmlinuz 2 4 27 xen0 BACKUP cp boot System map 2 4 27 xenO0 boot System map 2 4 27 xen0 BACKUP cd usr src linux 2 4 27 xen0 arch xen boot cp bzImage boot vmlinuz 2 4 27 xen0 cd usr src linux 2 4 27 xen0 cp System map boot System map 2 4 27 xenO reboot How do I use it Ivm04 An overview of some of the key LVM commands pvcreate This initialises a disk device or disk partition for use with LVM If this is a disk partition then the filesystem on the partition needs to be of type Ox8e i e Linux LVM this can be accomplished with fdisk If you are going to use a whole disk device then the device must not have a partition table again fdisk can be used for this So lets say we want to use dev sda1 dev sdb3 dev sdc as our physical volumes and we have ensured that they meet the requirements above pvcreate dev sdal dev sdb3 dev sdc vgcreate This creates a volume group and takes as parameters the physical volumes that have already been initialised using pvcreate Following from our example above vgcreate VolGrpl dev sdal dev sdb3 dev sdc where VolGrp1 is the name that we are giving to this volume group lvcreate Once we have a volume group w
14. dd button brings up a wizard for adding new devices When adding a new hard disk the user is presented with an option for creating a new blank hard disk or using an existing hard disk maybe a clone The main cause for concern when adding new a hard disk is correct configuration of the bootloader If a new existing hard drive is added to the VM during boot up the VM may boot into the second hard drive To ensure that the user has full control and choice over which hard disk is used during bootup the bootloader must only be present on one of the hard drives the one required to control the VM Once a new hard disk has been attached using VMware it will be completely blank and therefore needs to have an OS installed As by default the VM will boot straight into the primary hard disk containing the bootloader file which already has Red Hat installed the VM needs to be instructed to boot using the disk image in comment out the first two lines the CD drive again in order to run Red Hat Installer This is done by pressing the Esc key during the initial black VMware startup screen The user will be presented with the Boot Menu from which the CD ROM Drive option should be selected Red Hat can now be installed onto the new hard disk Alternatively another method for this process is by taking the bootdisk img file and using it in the floppy drive The bootdisk img file can be obtained b
15. e can create logical volumes which is precisely what lvcreate does When creating a LV you should specify its size L which VG you would like the LV to be created from since it 1s perfectly possible that you have a number of Volume Groups and possibly its name n So to create a 1 5Gb LV called 1va1 from VolGrp1 lvcreate L 1536 n lval VolGrpl e Ivscan This scans for the presence of any logical volumes and produces a report which is output to the terminal e vgscan As above but for volume groups e Ivremove This can be used to remove a LV For instance to remove the logical volume 1va1 created above lvremove dev VolGrp1 lval e vgreduce This will remove a PV from a VG For example if you would like to remove the volume dev sdc 12 vgreduce VolGrp1 dev sdc Alternatively if you don t specify a PV then all unused Physical Volumes will be removed from the Volume Group e vgextend This allows you to add a new PV toa VG for instance if you are running out of storage vgextend VolGrp1 dev sdd space in your VG So the above would add a new disk dev sdd that we have available to VolGrpl As you can see LVM is pretty straightforward to use In a virtualised environment such as VMWare it is ideal since if you start to run out of space in a VG you can just add a new
16. iguration may be written by hand however by supplying the xm create utility with the n flag the SXP configuration will be printed to the terminal For instance to generate the SXP configuration for the dom l config file the command would be xm create nf domlconfig The SXP configuration which is output can then be re directed to an sxp file for later use xm create nf domlconfig gt dom1SXPconfig sxp To create a domain using an SXP configuration note the use of uppercase F xm create F domiSXPconfig sxp 6 Note using the above example the first line of the file dom1SXPconfig sxp would read using config file domlconfig This line needs to be removed if the sxp file is to be used for domain creation or xend will produce the error Error Error creating domain missing vm name Alternatively using the q option will suppress printing the name of the configuration file being used ie xm create qnf dom1config gt domlconfigSXP sxp 3 Using the Command Line The third option may be the most convenient if you wish to specify a domain on demand i e if you aren t able to previously predict what resources your domain should be given This is straightforward with values being specified as property value when issuing the xm create command This is best illustrated with an example xm create name Dom9
17. l following the lapse of a predefined time interval Basically the boot loader is responsible for loading the kernel into memory and executing it e Invocation of the kernel This would mount the root file system perform preliminary memory and other hardware checks and then spawn the init process Booting a Xen Domain other than domain 0 which is a special case differs in that there is no need for allocation of a boot partition A domain thus needs at minimum just two partitions one of these is used as the root file system and the other is used as the swap space The size of these is up to the user but the root file system size is dictated by the size of the Linux installation which is placed therein The boot process differs from the typical scenario above in that the kernel file is provided by Domain 0 itself and a pivot_root call is made for changing the root file system to the one defined for the domain 2 2 Xen Management Tools The Xen toolbox is comprised of xend the Xen Management Daemon and xm The Xen Grand Unified Management Application A brief overview is provided to both of these tools below xen01 xend e What is it The Xen Management Daemon is a Python program whose interface is provided by a shell script This is responsible for amongst other things providing the console server e g for obtaining a console to a booted domain Another important functio
18. n 3 root desktop is localhost localdomain 3 RealVNC can be downloaded from http www realvnc com download free html There are packages for x86 Linux and for RedHat users there is an 1386 RPM package Information regarding installation and troubleshooting can be found on the website vnc01 Furthermore there are documentation packages that can be downloaded in addition to the application package If you are using the RedHat RPM installation is very straight forward rpm i vnc 4 0 1 i1386 rpm How do I use it First a password needs to be set which will be used to allow remote vncviewers to connect to the desktop being offered by a vncserver Obviously the installation needs to be done on both domain 0 and the non zero domain whose desktop you will be accessing On the host which will be running the vncserver you can set the password by issuing the command vncpasswd This will prompt for a password and then ask you to verify this Once this has been done the vncserver can be invoked The server can be used without any options the default geometry will be 1024x768 and the next available display number will be taken the vncserver manual pages provide more information regarding the various options for example you can specify which display number vncserver is to use To run the vncviewer on the client machine in this case Xen Domain 0 you will need to know the I P address of the machi
19. n performed by xend is management of Xen virtual networking which is achieved through the use of three shell scripts that are executed by xend following the occurrence of certain events How do I use it Xend is invoked from the command line and must be provided with a single parameter from the set start stop restart This must be run as root as calls will be made to privileged system management functions Trying to use the domain management application xm before xend start has been invoked will result in an error 111 Connection Refused Error error connecting to xend is xend running Where does it live etc rc d init d xend This is a script to facilitate for xend to be started by default every time the system boots This can be achieved by using chkconfig for example chkconfig level 12345 add xend The chkconfig utility updates and queries run level information for system services It allows you to set which services the nif process is required to start dependant on the run level This requires only the presence of an appropriate script in etc rc d init d chkconfig will then handle the creation of symbolic links in the correct rc d directories e g etc rc d rc2 d for run level 2 See the chkconfig manual pages for more information usr lib python2 2 site packages xen xend This directory contains all the python source and bytecode files which c
20. ne running the server as well as the display number the server is using this information is output to the terminal when the vncserver is invoked This is all best explained with the aid of an example DOMAIN 0 Install RealVNC lt lt set up vncserver on non zero domain gt gt 4 Start the vncviewer vncviewer 192 168 174 111 3 amp 5 Enter the password at the prompt Once the TWM window manager is displayed an X Terminal will be provided The x server can be invoked by executing cd etc X11 xinit Xclients Y VNC localhost locald Y VNC localhost localdomain 1 root roots Home S Start Here 8 rootalocalhost Elle Edit View Te root localhost root Linux localhost loca 6 1386 GNU Linux root localhost root anaconda ks cfg ins root localhost root Terminal S Accessories S Accessories E Accessories amp Accessories beg Graphics yp Graphics dia Graphics d Games intemet intemet amp office gt me gt Preferences Egg Preferences Ei Preferences amp office 5 Programming 8 Programming E Programming gt Eg Preferences E a More Sound amp Video Applications gt aaa e System Settings 2 System Settings E System Settings aud player I sound amp video System Tools Sap System Tools Se System Tods co player ae Brey PB Hep ZA Sound Recorder El System Settings kg System Tools poms Tolder ig Home Folder 148 Home Folder 149 Volume Control a
21. ollectively provide the functionality offered by xend usr sbin xend This is the script which provides the interface to xend that allows command line invocation etc xen scripts This directory contains the three networking scripts that are called by xend to provide virtual networking xm e What is it This provides a number of utilities for managing xen from the command line The general format of an xm command is xm command switches arguments variables Commands are provided for creating a domain listing active domains destroying a domain obtaining a console to an active domain as well as migrating a domain to name but a few A full listing of commands can be obtained by issuing the command xm help e How do I use it As previously explicated in order that xm be used xend needs to be running Information regarding domain specification and creation can be found in Section 2 3 e Where does it live usr lib python2 2 site packages xen xm This is the directory containing the python source code and byte code files used by xm usr sbin xm This is the shell script that provides the interface for xm to be invoked from the command line 2 3 Domain Specification and Creation A domain is defined by a number of properties that are set during domain creation A full listing of these properties can be obtained by typing xm help create more
22. oted that the above is only an example the two VDEV names don t have to be those given above although they cannot be completely arbitrary The first two letters specify the device type sd for scsi hd for IDE xd for XT disks the third letter specifies the drive sda is the first scsi drive sdb is the second etc and the number specifies the partition A configuration file exists which sets the values of the domain properties to the default values this is the file etc xen xmdefconfig So if you type xm create at the command line and nothing else xen will try and create a domain based on the values in xmdefconfig A domain may be created in one of three ways using a python configuration file using an sxp configuration file or setting values at the command line 1 Python Configuration File The file xmdefconfig is a python configuration file and as such can be used as a template A copy of this file can be made for use with a particular domain This file should then be edited to reflect your choice of values for the various domain properties Assuming that the configuration file has been called dom1config the domain creation command will be xm create f domlconfig Where the f option specifies that the specified python configuration file should be used instead of the default xmdefconfig 2 SXP Configuration File SXP is the internal configuration format that is used by Xen An SXP conf
23. ough the wizard it must still be installed For an installation of Red Hat 9 the required disk images can be obtained from http ftp redhat com pub redhat linux 9 en iso i386 The files needed are shrike 1386 disk1 1so shrike 1386 disk2 1so shrike 1386 disk3 1so Some problems have been faced when attempting to install Red Hat 9 using normal CDs which is why use of the disk images has been suggested 1 2 Installing Red Hat 9 Clicking on the Edit virtual machine settings link displays a dialog box In the Hardware tab a list of the VMs devices is shown To install Red Hat 9 click on the CD ROM device and within the Connection section select Use ISO image The location of the iso image shrike 1386 disk1 iso must be provided below Once set clicking on the Start this virtual machine link will boot up the VM and start the Red Hat installation wizard 1 3 Cloning the Red Hat Virtual Machine To clone the Red Hat VM a copy must be made of the folder containing all of its files Within the folder the vmware text document must be amended The MAC address needs to be temporarily manually assigned as follows Change the ethernet0 generatedAddress value For example ethernet0 generatedAddress 00 0c 29 3f 86 9d becomes ethernet0 generatedAddress 00 50 56 00 00 01 VMware will then automatically assign it a value during bootup There are now two identical Red Hat Virtual Machines alre
24. root dev sda2 initrd initrd version img boot dev sda Se odb db db db db db db db 3k default 0 timeout 10 splashimage hd0 0 grub splash xpm gz title Red Hat Linux 2 4 20 8 root hd0 0 kernel vmlinuz 2 4 20 8 ro root LABEL initrd initrd 2 4 20 8 img title Xen XenoLinux 1 2 unstable root hd0 0 kernel xen gz dom0_mem 131072 com1 115200 8n1 noht console coml module vmlinuz 2 4 27 xen0 ro root dev sda2 console tty0 lt Sample grub conf gt The first line dictates the option that will be present in the splash screen title Xen XenoLinux 1 2 unstable The second line specifies that root is to exist in the first hard drive nao in its first partition o this is where to look for the kernel root hd0 0 The third line specifies which kernel file to use within the first partition of the first hard drive followed by some parameters kernel xen gz dom0 mem 131072 com1 115200 8n1 noht console coml And finally the fourth line adds a module for domain 0 specifying its root destination and kernel file module vmlinuz 2 4 27 xen0 ro root dev sda2 console ttyO Further information about the grub conf file and its modification can be found at http www cpqlinux com grub html 1 8 Adding New Hard Disks New hard disks can be added very easily using VMware In the Virtual Machine Settings dialog the Hardware tab provides the option for adding devices Clicking the A
25. taken to implement this two of which are described below The feasibility of each is very much dependant on the user circumstances and work environment Furthermore it should obviously be kept in mind that the number of partitions that can be created is restricted by the size of the physical hard disk s when working in a virtualised environment such as VMWare 3 1 Adding a new Hard Disk If you are working in a virtualised environment for instance Xen domain 0 is installed on a VMWare Virtual Machine then adding a new hard disk for each domain is a straight forward way of handling storage management This can be implemented in one of two ways The root partition needs to have a Linux installation therein You can either create a hard disk complete with two partitions one of which has Linux installed on it as required by a domain and then clone this a number of times for each domain or you can start a new custom installation for each domain If you are using VMWare cloning a hard disk is simply a matter of making a copy of the virtual PV PV e g dev sdc e g dev sdb2 VG extents disk file and giving it an appropriate name Then this copied disk can be added to the machine running Domain 0 so that it can be made available for use by a non zero domain 3 2 LVM Logical Volume Management LVM can be used to overcome the problems associated with repartitioning a file system It is difficult to pre empt the n
26. ting and choosing properties which opens a dialog box Within this dialog box the destination of the Host Folder on the host operating system from which the user wishes to share files must be specified 1 6 Converting the Red Hat VM into XEN The files needed for the Xen installation process are the version or date values may differ the most recent version of the files should be used 1 xen 2 0 3 install tgz found at http www cl cam ac uk Research SRG net os xen downloads html 2 Twisted 1 3 0 tar gz found at http twistedmatrix com products download 3 bridge utils 0 9 6 1 1386 rpm found at http bridge sourceforge net download html Once obtained the files should be placed in the shared folder for use by the VM They can then be found within the VM in the mnt hgfs directory Installation of 2 and 3 as above is required before installation of xen can begin Installation procedure bridge utils 0 9 6 1 i386 rpm Copy the file from the shared folder to your home directory e g home marios Then the installation is simply a case of issuing rpm i filename cd mnt hgfs shared_folder cp bridge utils 0 9 6 1 i386 rpm home marios cd home marios rpm i bridge utils 0 9 6 1 i386 rpm Twisted 1 3 0 tar gz As above first copy the file to your home directory Then you need to expand the archive and use the included python build and
27. tion 0ooooocnooccccnnononcnononononnnnnnnnonnnnnnnnnrrnnnnn rr rro nennen ener ien nnne innere inrer en nnnn rennen 1 1 5 Installing VMware Tools e con ev en eene l 1 1 6 Converting the Red Hat VM into XEN vire ersen easar nrnna eene nennen nennen enhn rennen aesan evor rennen 2 1 7 Editing the orub cont files des epe enu ena e e dpa mines 2 18 Adding New Hard Disks als 3 1 9 Modityihig fstab eei re pou en tp eme nd tie dieu v p p ne rens 3 Dee MISTING CoD 2 I Introduction s oce e ed e d ee ei et 4 2 2 Xen Management To0l 3 4 eee Ne ER eR hse Ru 4 2 3 Domain Specification and Creation ssssssssssseseeseseeee esee nenne nn nn nan nr nr nan n nn r einn ee nnne enne 5 2 4 Domain Col A e ee 6 2 4 RBALMNG 5o n aeo Gm ele eo en e e tee dts ola deeds eco din 7 1 Using VMware Workstation 4 5 The VMware Workstation 4 5 can be obtained from WWW VMWare com 1 1 Creating a Virtual Machine New Virtual Machines can easily be created by clicking the New Virtual Machine icon and following the provided wizard Through the wizard the memory allocation network type and disk drive can be configured Choosing the custom configuration at the beginning of the wizard provides the user with more control over these parameters Once the wizard has been followed through a virtual machine has been created Although the guest operation system to be used for the VM has been chosen thr
28. umber and sizes of the partitions that you would like to make available for Xen domains Making a guess is risky since it could be the case that you will need to at some point make backups of your file systems format them and then re partition your disks according to some new scheme which will best suit your needs at the time Please note that this is by no means intended as a full on LVM tutorial but rather as an introduction to how LVM can be used to implement a flexible and expandable storage solution for your Xen Domains lvm03 e How does it work To best understand the following some definitions are required Ivm02 Physical Volume PV A physical storage resource that is going to be made available for use by LVM This can either be a disk partition e g dev sdb2 or it can be a whole disk e g dev sdb Volume Group VG A virtual storage pool which is the amalgamation of all Physical Volumes that have been placed in a VG The basic unit of measurement for a VG is the extent By default each extent is 4mb in size although this can be changed during VG creation Logical Volume LV A logical partition created from resources taken from a Volume Group The following figure offers a graphical representation of the key LVM components PV PV e g dev sde e g dev sdb1 The key components of LVM LVM allows you to change the size of a LV dynamically and whilst it is in use There is no data loss
29. untarred into the home directory the vmware install pl file must be executed This will run through the installation for VMware Tools offering options along the way for which the default settings are generally suitable At the end of the installation process an Execution aborted Message will be displayed this occurs because the final part of the installation must be executed out of an XFree86 session This final stage can be completed by pressing Ctrl Alt F2 which takes the user out of the XFree86 session to the command line Here once logging in a root the vmware config tools pl installer must be executed which can be found in the usr bin directory Again the default options are suitable for the installation and this time the installation will conclude completely Pressing Ctrl Alt F7 takes the user back to the XFree86 session VMware Tools are now installed and the blue warning saying You do not have VMware Tools installed at the bottom left of the VMware workstation window should now have disappeared Configuring Shared Folders Now that VMware tools have been installed the shared folder function can be configured The VM must first be powered off In the Virtual Machine Settings dialogue box that appears from clicking the Edit virtual machine settings link choose the Options tab This tab shows the status of the Shared Folders settings this can be enabled by selecting the Shared Folders set
30. virtual hard disk to your VMWare Virtual Machine i e Xen Dom 0 and then go through the steps of initialising it pvcreate and then add it to your VG using vgextend As explained earlier it is required that the partition assigned to a non zero domain as the root filesystem needs to have a Linux installation on it The problem encountered in doing this was that the RedHat installer would not allow a Logical Volume to be used as an installation target The workaround is to have a clean Linux installation on another partition and simply copy all files from that to your Logical Volume typically you would need to mount both filesystems to some known location copy the files over this is a simple matter of using the cp utility e g cp d destination directory and then ensure that you edit the etc fstab on the Logical Volume as explained in section 2 3 Domain Specification and Creation Finally a note on how the LVM logical volumes are referenced in case this is not clear from the above explanations A device file is created for all devices used by Linux in the dev directory so for instance the hard disk sdb will have the file dev sdb created for the Operating System to interact with it This convention is still true for LVM volumes except that the Volume Group name is included as part of the file path Thus the Logical Volume 1va1 that has been created in the VolGrp1 Volume Group is referenced as dev
31. which can be found in the etc directory SLABEL ext3 defaults 11 LABEL boot boot ext3 defaults 1 2 dev sdal boot ext3 defaults 12 dev sda2 ext3 defaults 11 none dev pts devpts gid 5 mode 620 0 0 none proc proc defaults 00 none dev shm tmpfs defaults 0 0 dev sda3 Swap Swap defaults 0 0 dev cdrom mnt cdrom udf iso9660 noauto owner kudzu ro 00 Figure 1 An Example fstab File More information about fstab can be found at www tuxfiles org linuxhelp fstab html 2 Using Xen 2 1 Introduction A typical Linux installation requires the use of at least three disk partitions One is used as the boot partition another as i e the root file system and the third as swap space implementation of virtual memory A simplistic view of the boot sequence for such an installation would then be as follows lin01 e BIOS performs memory integrity checks and looks for the MBR Master Boot Record this would typically reside on the first sector of the hard drive e The MBR utilises a partition table which gives details e g size type and starting cylinder of up to four partitions One of these is flagged as bootable and will eventually be mounted as boot The boot loader e g Grub or LILO will also reside on this partition e Invocation of the boot loader In a multi boot environment the boot loader would await instruction as to which OS kernel is to be booted or boot the default kerne
32. y mounting the RedHat 9 1386 1 1s0 CD image into the cdrom drive in Red Hat The bootdisk img can be found in the images directory This file can then be passed to the host OS using the Shared Folder capability Using this floppy image in the virtual floppy drive in the same way the CD images were used will boot the VM into the Red Hat installer in which the second hard disk can be chosen as the installation destination The installer can then be followed through as described previously New hard drives can then be added to the grub conf file by adding the following lines title Second Red Hat Linux 2 4 20 8 root hd1 0 kernel vmlinuz 2 4 20 8 ro root dev sdb2 hdc ide scsi initrd initrd 2 4 20 8 img and so on This time using the line root hd1 0 pointing to the first partition of the second hard disk for root and so on Many extra hard disks can then easily be added using the existing hard disk option and cloned hard disks provided the clones do not contain the bootloader 1 9 Modifying fstab When adding new hard disks problems can also occur if linux attempts to mount both of the hard disks simultaneously to the same mount point fstab is a configuration file in which all information about a systems partitions and storage devices is contained including the information which tells linux where and how to mount these partitions and storage devices Make the following changes in bold to the fstab file
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