VMs can be installed from:
The installation of paravirtual Linux guests is complicated by the fact that a Xen-aware kernel must be booted, rather than simply installing the guest using hardware-assistance. This does have the benefit of providing near-native installation speed due to the lack of emulation overhead. XenServer supports the installation of several different Linux distributions, and abstracts this process as much as possible.
To this end, a special bootloader known as eliloader is present in the control domain which reads various other-config keys in the VM record at start time and performs distribution-specific installation behavior.
install-repository - Required. Path to a repository; ‘http’, ‘https’, ‘ftp’, or ‘nfs’. Should be specified as would be used by the target installer, but not including prefixes, e.g. method=.
install-vnc - Default: false. Use VNC where available during the installation.
install-vncpasswd - Default: empty. The VNC password to use, when providing one is possible using the command-line of the target distribution.
install-round - Default: 1. The current bootloader round. Not to be edited by the user (see below)
eliloader is used for two rounds of booting. In the first round, it returns the installer initrd and kernel from /opt/xensource/packages/files/guest-installer. Then, on the second boot, it removes the additional updates disk from the VM, switches the bootloader to pygrub, and then begins a normal boot.
This sequence is required since Red Hat does not provide a Xen kernel for these distributions, and so the XenServer custom kernels for those distributions are used instead.
Similar to the RHEL4.4 installation, except that the kernel and ramdisk are downloaded directly form the network repository that was specified by the user, and switch the bootloader to pygrub immediately. Note that pygrub is not executed immediately, and so will only be parsed on the next boot.
The network retrieval enables users to install the upstream Red Hat vendor kernel directly from their network repository. An updated XenServer kernel is also provided on the xs-tools.iso built-in ISO image which fixes various Xen-related bugs.
This requires a two-round boot process. The first round downloads the kernel and ramdisk from the network repository and boots them. The second round then inspects the disks to find the installed kernel and ramdisk, and sets the PV-bootloader-args to reflect these paths within the guest filesystem. This process emulates the domUloader which SUSE use as an alternative to pygrub. Finally, the bootloader is set to pygrub and is executed to begin a normal boot.
The SLES 10 installation method means that the path for the kernel and ramdisk is stored in the VM record rather than in the guest menu.lst, but this is the only way it would ever work since the YAST package manager doesn’t write a valid menu.lst.
The CentOS installation mechanism is similar to that of the Red Hat installation notes above, save that some MD5 checksums are different which eliloader recognizes.