The following lists some steps which are commonly necessary after installing Xen on a new host.
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For a Xen System to boot correctly, the Xen hypervisor needs to be started before your Dom0 Linux (or BSD) kernel. This means that the bootloader needs to load and boot Xen first and then chain-boots the Dom0 kernel. Typically, your bootloader configuration gets automatically updated by your chosen distro: you install your Dom0 distro, then your Xen packages, which should update your bootloader configuration accordingly.
However, this merely set up a number of defaults for Xen. If you want to use specific start-up options for Xen - for a list see [Xen Command Line Options - you will need to manually change bootloader options in the appropriate configuration file (e.g. /boot/grub/grub.conf for grub).
Boot Managers for Xen VMs
Xen comes with two boot managers for Xen virtual machines.
- PvGrub: PV-GRUB (ParaVirtual Grub) is a boot manager for Xen virtual machines. It is a safer (as in designed to be more secure - see the technical details section) and more efficient alternative to PyGrub to boot domU images: unlike pygrub it runs an adapted version of the grub boot loader inside the created domain itself, and uses the regular domU facilities to read the disk mounted as root directory, fetch files from network, etc. It also eventually loads the PV kernel and chain-boots it.
- PyGrub: enables you to start Linux domUs with a kernel inside the DomU instead of a kernel that lies in the filesystem of the dom0. This means easier management - each domU manages its own kernel and initrd, meaning you can use the built-in package manager to update the kernels, instead of having to track and update kernels stored in your dom0. It also allows easy migration of HVM'ed Linuxes - there's no need to extract the installed kernel & initrd.
When running Xen on a host it is normal to require some particular setup of the network stack in order to provide a way for Virtual Machines to access the network. The most common of these is to use bridging.