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--- linux:system:grub [2023/08/06 06:58] – oscar
+++ linux:system:grub [Unknown date] (current) – removed - external edit (Unknown date) 127.0.0.1
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-====== GRUB 2 ======
-----
-===== Grub Configuration =====
-GRUB settings are stored in the following locations:
-  * **/etc/default/grub** file Edit this file to change GRUB2’s settings.
-  * **/etc/grub.d/** directory contains additional scripts that are loaded by the /etc/default/grub file. For example, on Ubuntu, there are scripts here that configure the default theme. There’s also an os-prober script that checks the system’s internal hard drives for other installed operating systems — Windows, other Linux distributions, Mac OS X, and so on — and automatically adds them to GRUB2’s menu.
-  * **/boot/grub/grub.cfg** file that’s created by update-grub and read at boot.
-When you run the update-grub command, GRUB automatically combines the settings from the /etc/default/grub file, the scripts from the /etc/grub.d/ directory, and everything else, creating a /boot/grub/grub.cfg file that’s read at boot. In other words, to customize your GRUB2 settings, you’ll have to edit the **/etc/default/grub** file and then run the **update-grub** command. Subsequently install/update the Grub loader in the disk.
-    # /etc/default/grub
-    # update-grub
-    # grub-install /dev/sdX
-    # grub-install --recheck /dev/sdX
-===== Probe installed OS =====
-Open a terminal and run the os-prober command with root privileges. This will search for other operating system installations besides the current distro you’re booted into.
-  $ sudo os-prober
-It should find your Linux distro, the Windows installation, and possibly a memory test installation or recovery partition. To add these findings to the GRUB menu, execute the update-grub command with root permissions.
-  $ sudo update-grub
-The output should show that Windows 10 has been found and added to the GRUB boot menu.
-===== Repair, Restore, or Reinstall Grub 2 with Live USB =====
-Grub 2 typically gets overridden when you install Windows or another Operating System. To make Linux control the boot process, you need Reinstall (Repair/Restore) Grub using a Live CD.
-Create a live USB and boot system from USB
-Mount the partition your broken Linux installation is on. If you are not sure which it is, launch GParted (included in the Live CD) and find out. It is usually a EXT4 Partition. Replace the XY with the drive letter, and partition number, for example: sudo mount /dev/sda1 /mnt.
-<code>
-# mount /dev/sdXY /mnt
-</code>
-Now bind the directories that grub needs access to to detect other operating systems, like so.
-<code>
-# mount --bind /dev /mnt/dev
-# mount --bind /dev/pts /mnt/dev/pts
-# mount --bind /proc /mnt/proc
-# mount --bind /sys /mnt/sys
-</code>
-Internet access
-For internet access inside chroot:
-<code>
-# mv /mnt/etc/resolv.conf /mnt/etc/resolv.conf.org
-# cp /etc/resolv.conf /mnt/etc/resolv.conf
-</code>
-Now we jump into that using chroot.
-<code>
-# chroot /mnt
-</code>
-Now install, check, and update grub. This time you only need to add the drive letter (usually a) to replace X, for example: grub-install /dev/sda, grub-install –recheck /dev/sda.
-<code>
-# grub-install /dev/sdX
-# grub-install --recheck /dev/sdX
-</code>
-Alternatively, in case of persistent problems, you can purge and reinstall grub2, make new config files:
-<code>
-apt-get remove --purge grub-pc grub-common
-apt-get install grub-pc
-grub-mkconfig
-update-grub
-grub-install /dev/sda
-</code>
-Now grub is back, all that is left is to exit the chrooted system and unmount everything:
-<code>
-# exit
-# umount /mnt/sys
-# umount /mnt/proc
-# umount /mnt/dev/pt
-# umount /mnt/dev
-# umount /mnt
-</code>
-Shut down and turn your computer back on, and you will be met with the default Grub2 screen.
-===== Customize boot layout =====
-For customizing the layout of the Grub startup screen at boot, the files are located in:/boot/grub.
-The sample below illustrates adding a background image and changing the font size.
-Copy the background images to the folder: /boot/grub. Remember that other partitions might not yet be mounted and available at boot time. Update /etc/default/grub as follows:
-  #nano /etc/default/grub
-  Modify Lines:
-  GRUB_BACKGROUND=/boot/grub/Katwijk-Silouet-edge-grain1-grub-1024x768.jpg
-  GRUB_GFXMODE=1024x768
-If you change this file, run 'update-grub' afterwards to update /boot/grub/grub.cfg.
-  update-grub
-Currently a grub2 wallpaper image cannot be larger than 1024×768px, and it will (configured by default) be stretched to match your gfx resolution. One way to give the illusion of a 16:9 grub wallpaper is to take an existing 16x9 wallpaper and scale it to the 4:3 image of size 1024x768, and set the grub gfx mode for example to GRUB_GFXMODE=1920x1080, when grub loads and stretches that image its aspect ratio will appear similar to the original.