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Xen traditionally allows customizing guest behavior by passing arguments to the VM kernel via the kernel command line. This is no longer possible when using GRUB with Xen, as the kernel command line is decided by the GRUB configuration file within the guest, not data passed to the guest by Xen. To work around this limitation, enable GRUB to parse a command line passed to it by Xen, and expose data from the command line to the GRUB configuration as environment variables. These variables can be used in the GRUB configuration for any desired purpose, such as extending the kernel command line passed to the guest. The command line format is inspired by the Linux kernel's command line format. To reduce the risk of misuse, abuse, or accidents in production, the command line will only be parsed if it consists entirely of 7-bit ASCII characters, only alphabetical characters and underscores are permitted in variable names, and all variable names must start with the string "xen_grub_env_". This also allows room for expanding the command line arguments accepted by GRUB in the future, should other arguments end up becoming desirable in the future. Signed-off-by: Aaron Rainbolt <arraybolt3@gmail.com> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'