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:md: ./modules
= Bootloading with *GRUB2*
[[bootloading-with-grub2]]
*GRUB2* is the latest version of *GNU GRUB*, the _GRand Unified Bootloader_.
A bootloader is the first software program that runs when a computer
starts. It is responsible for loading and transferring control to the
operating system kernel. In Fedora, the kernel is Linux. The kernel then initializes
the rest of the operating system.
*GRUB2* is the follower of the previous version *GRUB* (version 0.9x). The original version is available under the name *GRUB Legacy*.
Since Fedora 16, *GRUB2* has been the default bootloader on x86 BIOS
systems. For upgrades of BIOS systems, the default is also to install
*GRUB2*, but you can opt to skip bootloader configuration entirely.
include::{md}/proc_installing-grub2-on-bios-system.adoc[leveloffset=+1]
include::{md}/proc_installing-grub2-on-efi-system.adoc[leveloffset=+1]
include::{md}/proc_adding-other-operating-systems-grub2.adoc[leveloffset=+1]
include::{md}/proc_setting-default-entry-for-grub2.adoc[leveloffset=+1]
include::{md}/proc_restoring-bootloader-using-live-disk.adoc[leveloffset=+1]
include::{md}/proc_using-grub2-prompt.adoc[leveloffset=+1]
include::{md}/proc_booting-with-configfile-on-different-partition.adoc[leveloffset=+1]
include::{md}/proc_setting-password-for-interactive-edit-mode.adoc[leveloffset=+1]
include::{md}/proc_solving-absent-floppy.adoc[leveloffset=+1]
include::{md}/proc_using-old-graphics-modes.adoc[leveloffset=+1]
include::{md}/proc_enabling-serial-console-grub.adoc[leveloffset=+1]
[[further-reading]]
== Further Reading
* http://www.gnu.org/software/grub/manual/grub.html
See a typo, something missing or out of date, or anything else which can be
improved? Edit this document at https://pagure.io/fedora-docs/quick-docs.

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:md: ./modules
= Installing *GRUB2*
[[installing-grub2]]
= Bootloading with *GRUB2*
[[bootloading-with-grub2]]
*GRUB2* is the latest version of *GNU GRUB*, the _GRand Unified Bootloader_.
A bootloader is the first software program that runs when a computer

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= Adding other operating systems to the *GRUB2* menu
[[adding-other-operating-systems-to-the-grub-2-menu]]
[[adding-other-operating-systems-grub2]]
Normally, *GRUB2* is preset to boot multiple operating systems during the Fedora installation process. If you can, it is advisable to install non-Linux operating systems first. Then, during the installation process, all those operating systems and their locations will be discovered and properly set.
Sometimes, however, you cannot use this approach and you will have to create the bootloader configuration file again to enable it to boot more operating systems.
Adding other records into the *GRUB2* menu only means to run `grub2-mkconfig` command to regenerate the configuration files. During this process, all operating systems known to the system will be added into the configuration. By reinstalling *GRUB2* into the MBR, this configuration will be used for further boots.
.Before you start
@ -12,18 +12,19 @@ Sometimes, however, you cannot use this approach and you will have to create the
.Procedure
. Install *GRUB2* into the MBR of your primary hard disk.
+
----
$ sudo grub2-install /dev/sda
----
. Recreate the *GRUB2* configuration file.
+
----
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
----
. Install *GRUB2* into the MBR of your primary hard disk.
+
----
$ sudo grub2-install /dev/sda
----
.More information
* The `grub2-mkconfig` command will add entries for all operating systems it can find.
* When problems appear, see the link:http://www.gnu.org/software/grub/manual/grub.html#Multi_002dboot-manual-config[GRUB manual] to solve issues with booting secondary operating systems.

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= Booting the system using a configuration file on a different partition.
[[booting-with-configfile-on-different-partition]]
If you end up in *GRUB2* boot prompt, it is also possible to boot using a _configfile_ that's located on another
partition, as is often the case with multi-boot systems containing Ubuntu and Fedora. To boot the system using a configuration files on a different partition:
.Procedure
. Load necessary modules to read the partitions.
+
----
insmod part_msdos
insmod xfs
insmod lvm
----
. Set the root partition.
+
----
set root='hd0,msdos1'
----
. Set the path to the configuration file.
+
----
configfile /grub2/grub.cfg
----
.More information
* The *hd0,msdos1* line shows the pertinent _boot_ partition, which holds the
`grub.cfg` file. The setting may be different on your system. See also xref:using-grub2-prompt[Using the GRUB2 boot prompt] for more information.

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= Creating the boot menu entries with UEFI bootloader
[[creating-the-boot-menu-entries-with-uefi-bootloader]]
When you power on your system, your firmware will look for EFI variables that tell it how to boot. On running systems, which have booted into the EFI mode and their EFI runtime services are working correctly, you can configure your boot menu with `efibootmgr`.
If not, `shim` can help you bootstrap. The EFI program
`/boot/efi/EFI/BOOT/fallback.efi` will look for files called `BOOT.CSV`
in your ESP and will add boot entries corresponding to them. The `shim` command
provides its own `BOOT.CSV` file that will add an entry for `grub2-efi`.
During the boot process, you can use the *EFI Shell* to invoke the `fallback.efi` profile to boot the system:
. Enter the boot partition.
+
----
> fs0:
----
. Navigate into the `EFI\BOOT` directory.
+
----
> cd EFI\BOOT
----
. Invoke the `fallback.efi` profile.
+
----
> fallback.efi
----
.More information
* If you have no boot entries at all, then just booting off your disk in
UEFI mode should automatically invoke `/boot/efi/EFI/BOOT/BOOTX64.EFI`,
which will, in turn, invoke `fallback.efi`.
* If you already have incorrect boot entries, you'll either need to delete
them or to modify `BOOT.CSV` to create new entries with different names.

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= Enabling Serial Console in GRUB2
[[enabling-serial-console-grub]]
To enable Serial console in grub:
.Procedure
. Edit the `/etc/default/grub` file.
. Adjust `baudrate`, `parity`, `bits`, and `flow` controls to fit your environment and cables, see the example.
+
----
GRUB_CMDLINE_LINUX='console=tty0 console=ttyS0,115200n8'
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
----
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].

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@ -20,6 +20,12 @@ $ dnf list installed | grep grub
.Procedure
. Create a configuration file for *GRUB2*.
+
----
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
----
. List block devices available on the system.
+
----
@ -34,12 +40,6 @@ $ lsblk
$ sudo grub2-install /dev/sda
----
. Create a configuration file for *GRUB2*.
+
----
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
----
. Reboot your computer to boot with the newly installed bootloader.
.More information

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@ -3,7 +3,7 @@
Normally, *GRUB2* will be installed and set up by the installer, *Anaconda*, during the installation process. You will probably never have to deal with manual installation of *GRUB2*. However, in certain situations , you will want to install *GRUB2* manually, especially if you need to repair the existing *GRUB2* installation or you want to change its configuration.
This procedure shows the steps to install *GRUB2* on a UEFI system on Fedora 18 or newer. The procedure consists of three parts.
This procedure shows the steps to install *GRUB2* on a UEFI system on Fedora 18 or newer. The procedure consists of four parts.
== Creating an EFI System Partition
[[create-an-esp]]
@ -87,3 +87,40 @@ $ sudo grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
`grubby` expects `/etc/grub2-efi.cfg` to be a symlink to the real
grub.cfg (for example `/boot/efi/EFI/fedora/grub.cfg`).
== Solving problems with UEFI bootloader
[[solving-problems-with-uefi-bootloader]]
When you power on your system, your firmware will look for EFI variables that tell it how to boot. On running systems, which have booted into the EFI mode and their EFI runtime services are working correctly, you can configure your boot menu with `efibootmgr`.
If not, `shim` can help you bootstrap. The EFI program
`/boot/efi/EFI/BOOT/fallback.efi` will look for files called `BOOT.CSV`
in your ESP and will add boot entries corresponding to them. The `shim` command
provides its own `BOOT.CSV` file that will add an entry for `grub2-efi`.
During the boot process, you can use the *EFI Shell* to invoke the `fallback.efi` profile to boot the system:
. Enter the boot partition.
+
----
> fs0:
----
. Navigate into the `EFI\BOOT` directory.
+
----
> cd EFI\BOOT
----
. Invoke the `fallback.efi` profile.
+
----
> fallback.efi
----
.More information
* If you have no boot entries at all, then just booting off your disk in
UEFI mode should automatically invoke `/boot/efi/EFI/BOOT/BOOTX64.EFI`,
which will, in turn, invoke `fallback.efi`.
* If you already have incorrect boot entries, you'll either need to delete
them or to modify `BOOT.CSV` to create new entries with different names.

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= Restoring the bootloader using the Live disk.
[[restoring-bootloader-using-live-disk]]
Sometimes, especially after a secondary operating systems has been installed, the master boot record gets damaged which then prevents the original Linux system from booting.
If this happens, it is necessary to reinstall *GRUB2* to recreate the original settings. The process not only discovers all installed operating systems, but usually adds them to the *GRUB2* configuration files, so they will all become bootable by *GRUB2*.
.Before you start
* Get the Fedora Live ISO from link:https://download.fedoraproject.org/pub/fedora/linux/releases/27/Workstation/x86_64/iso/Fedora-Workstation-Live-x86_64-27-1.6.iso[getfedora.org].
* Prepare a bootable device using the downloaded ISO, either a CD or a USB.
.Procedure
. Boot the Fedora live system from the bootable device you have created.
. Open the terminal.
. Examine the partition layout and identify the `boot` and the `root` partition.
+
----
$ sudo fdisk -l
----
+
If you are using the default Fedora layout, there will be one `/dev/sda1` partition that holds the `/boot` directory and one `/dev/mapper/fedora-root` that holds the root file system.
. Create the mount point for the root partition.
+
----
$ sudo mkdir -p /mnt/root
----
. Mount the root partition on the mount point.
+
----
$ sudo mount /dev/mapper/fedora-root /mnt/root
----
. Mount the boot partition in the `boot` directory of the filesystem that you have mounted in the previous step.
+
----
$ sudo mount /dev/sda1 /mnt/root/boot/
----
. Mount system processes and devices into the root filesystem in `/mnt/root`.
+
----
$ sudo mount -o bind /dev /mnt/root/dev
$ sudo mount -o bind /proc /mnt/root/proc
$ sudo mount -o bind /sys /mnt/root/sys
$ sudo mount -o bind /run /mnt/root/run
----
. Change your filesystem into the one mounted under `/mnt/root`.
+
----
$ sudo chroot /mnt/root
----
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].
. Exit this temporary root filesystem.
+
----
$ exit
----
. Your bootloader should be now restored. Reboot your computer to boot into your normal system.
+
----
$ sudo systemctl reboot
----

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= Setting default entry for *GRUB2*
[[setting-default-entry]]
Since `grub2-mkconfig` (and *os-prober*) cannot estimate which operating system, of those it finds, is to be marked as default, we usually are unable to predict the order of
the entries in `/boot/grub2/grub.cfg`. To change the default layout, we need to set the default based on the `name` or `title`.
.Before you start
. Open `/etc/default/grub` and make sure these lines exist in the file.
+
----
GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=false
----
. If you needed to change the content of the `/etc/default/grub`, apply the changes to `grub.cfg`.
+
----
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
----
.Procedure
. List all possible menu entries.
+
----
$ sudo grep -P "^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
----
. Select one of the displayed options and use it as an argument to set the default menu entry.
+
----
$ sudo grub2-set-default <menuentry>
----
. Verify the default menu entry
+
----
$ sudo grub2-editenv list
----
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].
.More information
If you understand the risks involved, you can manually modify the
`/boot/grub2/grub.cfg` file. In that case, set the number of the default operating system using the `set default` variable.
For example:
----
set default="5"
----
[NOTE]
====
If you edit the configuration file manually, the settings will be overwritten each time the `grub2-mkconfig` command runs.
====

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= Setting a password for interactive edit mode
[[setting-password-for-interactive-edit-mode]]
If you wish to protect the *GRUB2* interactive edit mode with a password, but allow ordinary users to boot the computer, you have to create a definition file where you set up this functionality:
.Procedure
. Create the `/etc/grub.d/01_users` file and write the following lines into the file.
+
----
set superusers="root"
export superusers
password root <password>
----
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].
.More information
You can encrypt the password by using *pbkdf2*. Use `grub2-mkpasswd-pbkdf2`
to encrypt the password, then replace the password line with:
----
password_pbkdf2 root grub.pbkdf2.sha512.10000.1B4BD9B60DE889A4C50AA9458C4044CBE129C9607B6231783F7E4E7191D8254C0732F4255178E2677BBE27D03186E44815EEFBAD82737D81C87F5D24313DDDE7.E9AEB53A46A16F30735E2558100D8340049A719474AEEE7E3F44C9C5201E2CA82221DCF2A12C39112A701292BF4AA071EB13E5EC8C8C84CC4B1A83304EA10F74
----
More details can be found at
https://help.ubuntu.com/community/Grub2/Passwords[Ubuntu Help: GRUB2
Passwords].
[NOTE]
====
Starting from Fedora 21, the `--md5pass` kickstart option must be used when using the `grub2-mkpasswd-pbkdf2` command.
====

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[[solving-absent-floppy]]
= Dealing with the "Absent Floppy Disk" Error
It has been reported by some users that *GRUB2* may fail to install on a partition's boot sector if the computer's floppy controller is activated in BIOS without an actual floppy disk
drive being present. Such situations resulted in an _Absent Floppy Disk_ error.
To workaround this issue, go into the rescue mode and follow the procedure in xref:installing-grub-2-on-a-bios-system[Installing GRUB2 on a BIOS system] *GRUB2*, but use the `--no-floppy` option with the `grub2-install` command.
----
grub2-install <target device> --no-floppy
----

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= Using the GRUB2 boot prompt
[[using-the-grub-2-boot-prompt]]
If improperly configured, *GRUB2* may fail to load and subsequently drop
to a boot prompt. To boot into the system, proceed as follows:
. Load the XFS and LVM modules
+
----
insmod xfs
insmod lvm
----
. List the drives which *GRUB2* sees:
+
----
grub2> ls
----
. Study the output for the partition table of the `/dev/sda` device. It may look similar to the following example on a dos partition table with three partitons.
will look something like this:
+
----
(hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1)
----
+
or similar to this output on a gpt partition table of the `/dev/sda` device with four
partitions.
+
----
(hd0) (hd0,gpt4) (hd0,gpt3) (hd0,gpt2) (hd0,gpt1)
----
. Probe each partition of the drive and locate your `vmlinuz` and `initramfs` files.
+
----
ls (hd0,1)/
----
+
The outcome of the previous command will list the files on `/dev/sda1`. If this partition contains the `/boot` directory, it will show the full name of `vmlinuz` and `initramfs`.
. Set the root partition.
+
----
grub> set root=(hd0,3)
----
. Set the desired kernel.
+
----
grub> linux (hd0,1)/vmlinuz-3.0.0-1.fc16.i686 root=/dev/sda3 rhgb quiet selinux=0
# NOTE : add other kernel args if you need them
# NOTE : change the numbers to match your system
----
. Set the desired `initrd`.
+
----
grub> initrd (hd0,1)/initramfs-3.0.0-1.fc16.i686.img
# NOTE : change the numbers to match your system
----
. Boot with the selected settings.
+
----
grub> boot
----
. To restore the bootloader's functionality, regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].

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= Using old graphics modes in bootloader
[[using-old-graphics-modes]]
The terminal device is chosen with GRUB_TERMINAL. For more information, see the link:http://www.gnu.org/software/grub/manual/grub.html#Simple-configuration[Grub manual].
Valid terminal output names depend on the platform, but may include
`console` (PC BIOS and EFI consoles), `serial` (serial terminal),
`gfxterm` (graphics-mode output), `ofconsole` (Open Firmware console),
or `vga_text` (VGA text output, mainly useful with Coreboot).
The default is to use the platform's native terminal output.
In Fedora, `gfxterm` is the default options. To get the legacy graphics modes:
.Procedure
. Edit the `/etc/default/grub` file.
. Set the `GRUB_TERMINAL` variable to one of the above mentioned options.
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].

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[[setting-default-entry]]
== Setting default entry
. Regenerate the *GRUB2* configuration file and reinstall the bootloader into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].
Due to `grub2-mkconfig` (and *os-prober*) we cannot predict the order of
the entries in `/boot/grub2/grub.cfg`, so we set the default by
name/title instead.
.Before you start
. Open `/etc/default/grub` and make sure these lines exist in the file.
+
----
GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=false
----
. Apply the changes to `grub.cfg` by running.
+
----
$sudo grub2-mkconfig -o /boot/grub2/grub.cfg
----
.Procedure
. List all possible menu entries.
+
----
$sudo grep -P "submenu|^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
----
. Set the desired default menu entry
+
----
$sudo grub2-set-default "<submenu title><menu entry title>"
----
. Verify the default menu entry
+
----
$sudo grub2-editenv list
----
.More information
If you understand the risks involved, you can manually modify the
`/boot/grub2/grub.cfg` file. In that case, set the number of the default operating system using the `set default` variable.
For example:
----
set default="5"
----

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