Create and Manage Virtual Machines on Xen
Posted on In Linux, VirtualizationIn this post, these content are introduced:
- Create and manage file-backed virtual block device (VBD) for virtual machines on xen.
- Install Fedora 11 via internet as DomU on top of xen.
- Manage virtual machines using xm.
Create file-backed VBD:
The actual space of VBD will be the amount of disk the virtual machine used. And it will be convenient if the virtual machine will be duplicated since the work is just copying the VBD file and changing some configurations.
Create a 20GB sparse file-backed VBD:
# dd if=/dev/zero of=vmdisk0 bs=1k seek=20480k count=1
Make a ext3 file system in the disk file:
# mkfs -t ext3 vmdisk0
Install Fedora 11 Linux via Internet:
First download the pxeboot kernel of Fedora 11 for installation via Internet. Download vmlinuz and initrd.img from here:
Create an installation profile f11.install:
name="F11INSTALL" memory=1536 disk = ['tap:aio:/home/xen/vmdisk0,xvda,w' ] vif = [ 'bridge=eth0' ] kernel = "/home/xen/fedora/vmlinuz" ramdisk = "/home/xen/fedora/initrd.img" vcpus=2 on_reboot = 'restart' on_crash = 'restart'
Here the blktap2 VBD driver is used. If the loopback backed driver is used, the disk like should be changed to:
disk = ['file:/home/xen/vmdisk0,xvda,w' ]
The virtual machine’s name is “F11INSTALL”, memory is 1.5G, CPU number is 2, disk, kernel and ramdisk is prepared in the above steps.
Start this virtual machine:
# xm create f11.install
Connect to this virtual machine’s console and complete the installation:
# xm console F11INSTALL
The installation of Fedora 11 will start. The URL of installation source I used during installation is:
http://download.fedora.redhat.com/pub/fedora/linux/releases/11/Fedora/x86_64/os/Load DomU:
Create a profile vm1.run for loading the virtual machine:
name="vm1" memory=1536 disk = ['tap:aio:/home/xen/vm1/vmdisk1,xvda,w' ] vif = [ 'bridge=eth0' ] bootloader = "/usr/bin/pygrub" vcpus=2 on_reboot = 'restart' on_crash = 'restart'
Here we use the PyGrub (“/usr/bin/pygrub”) as the bootloader. PyGrub starts Linux DomUs with the kernels that lie in the filesystem of the DomU instead of the kernels that lie in the filesystem of the Dom0. That makes the kernel update and management easier.
Then the DomU can be started using this profile:
# xm create vm1.run
The console of this DomU can be connected to:
# xm console vm1Manage DomUs:
Start Domu:
# xm create DomU_profileList running DomUs:
# xm list
Shutdown DomU:
# xm shutdown DomU_name
Console of DomU:
# xm console DomU_name
Top of DomUs:
# xm top
Reset a DomU:
# xm reset DomU_name
And others more which can be find in the xm manuals.
After configured a DomU, duplication of the DomU is easy: Just make a copy of the VBD file and the profile, and then change the profile.
I have set up 8 DomUs on the server. There are total 9 machines on top of xen and a lot of interesting things can be done with these “machines” ;)
# xm list Name ID Mem VCPUs State Time(s) Domain-0 0 1826 16 r----- 244.8 vm1 25 1536 2 -b---- 4.9 vm2 24 1536 2 -b---- 5.4 vm3 23 1536 2 -b---- 5.4 vm4 22 1536 2 -b---- 5.8 vm5 27 1536 2 -b---- 5.4 vm6 20 1536 2 -b---- 6.0 vm7 19 1536 2 -b---- 6.3 vm8 18 1536 2 -b---- 18.8
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