c7c9019165
This patch changes set_variables() so that it can use an external environment block when one is present. The variable next_entry is written into the external block, env_block is treated as read only, and all other variables are written into the normal file based envblk. A cleanup step is added to handle cases where GRUB at runtime writes variables into the external block because file based updates are not safe on a copy on write filesystem such as Btrfs. For example, the savedefault command can update saved_entry, and on Btrfs GRUB will place that update in the external block instead of the file envblk. If an older copy remains in the external block, it would override the newer value from the file envblk when GRUB first loads the file and then applies the external block on top of it. To avoid this, whenever a variable is updated in the file envblk, any same named key in the external block is deleted. Signed-off-by: Michael Chang <mchang@suse.com> Reviewed-by: Neal Gompa <ngompa13@gmail.com> Reviewed-by: Avnish Chouhan <avnish@linux.ibm.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'