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'
Colin Watson
authored
Some UEFI firmware is easily provoked into running out of space in its variable storage. This is usually due to certain kernel drivers (e.g. pstore), but regardless of the cause it can cause grub-install to fail because it currently asks efibootmgr to delete and re-add entries, and the deletion often doesn't result in an immediate garbage collection. Writing variables frequently also increases wear on the NVRAM which may have limited write cycles. For these reasons, it's desirable to find a way to minimise writes while still allowing grub-install to ensure that a suitable boot entry exists. Unfortunately, efibootmgr doesn't offer an interface that would let grub-install do this. It doesn't in general make very much effort to minimise writes; it doesn't allow modifying an existing Boot* variable entry, except in certain limited ways; and current versions don't have a way to export the expected variable data so that grub-install can compare it to the current data. While it would be possible (and perhaps desirable?) to add at least some of this to efibootmgr, that would still leave the problem that there isn't a good upstreamable way for grub-install to guarantee that it has a new enough version of efibootmgr. In any case, it's cumbersome and slow for grub-install to have to fork efibootmgr to get things done. Fortunately, a few years ago Peter Jones helpfully factored out a substantial part of efibootmgr to the efivar and efiboot libraries, and so it's now possible to have grub-install use those directly. We still have to use some code from efibootmgr, but much less than would previously have been necessary. grub-install now reuses existing boot entries where possible, and avoids writing to variables when the new contents are the same as the old contents. In the common upgrade case where nothing needs to change, it no longer writes to NVRAM at all. It's also now slightly faster, since using libefivar is faster than forking efibootmgr. Fixes Debian bug #891434. Signed-off-by:Colin Watson <cjwatson@ubuntu.com> Bug-Debian: https://bugs.debian.org/891434 Forwarded: https://lists.gnu.org/archive/html/grub-devel/2019-03/msg00119.html Last-Update: 2019-03-23 Patch-Name: efi-variable-storage-minimise-writes.patch