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The GRUB emulator is used as a debugging utility but it could also be used as a user-space bootloader if there is support to boot an operating system. The Linux kernel is already able to (re)boot another kernel via the kexec boot mechanism. So the grub-emu tool could rely on this feature and have linux and initrd commands that are used to pass a kernel, initramfs image and command line parameters to kexec for booting a selected menu entry. By default the systemctl kexec option is used so systemd can shutdown all of the running services before doing a reboot using kexec. But if this is not present, it can fall back to executing the kexec user-space tool directly. The ability to force a kexec-reboot when systemctl kexec fails must only be used in controlled environments to avoid possible filesystem corruption and data loss. Signed-off-by: Raymund Will <rw@suse.com> Signed-off-by: John Jolly <jjolly@suse.com> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> Signed-off-by: Robbie Harwood <rharwood@redhat.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'