8ddbdc3bc2
Refactor clean_grub_dir() to create a backup of all the files, instead of just irrevocably removing them as the first action. If available, register atexit() handler to restore the backup if errors occur before point of no return, or remove the backup if everything was successful. If atexit() is not available, the backup remains on disk for manual recovery. Some platforms defined a point of no return, i.e. after modules & core images were updated. Failures from any commands after that stage are ignored, and backup is cleaned up. For example, on EFI platforms update is not reverted when efibootmgr fails. Extra care is taken to ensure atexit() handler is only invoked by the parent process and not any children forks. Some older GRUB codebases can invoke parent atexit() hooks from forks, which can mess up the backup. This allows safer upgrades of MBR & modules, such that modules/images/fonts/translations are consistent with MBR in case of errors. For example accidental grub-install /dev/non-existent-disk currently clobbers and upgrades modules in /boot/grub, despite not actually updating any MBR. This patch only handles backup and restore of files copied to /boot/grub. This patch does not perform backup (or restoration) of MBR itself or blocklists. Thus when installing i386-pc platform, corruption may still occur with MBR and blocklists which will not be attempted to be automatically recovered. Also add modinfo.sh and *.efi to the cleanup/backup/restore code path, to ensure it is also cleaned, backed up and restored. Signed-off-by: Dimitri John Ledkov <xnox@ubuntu.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. 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'