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@@ -1,189 +1,195 @@
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- = GRUB 2
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+ = The GRUB2 Bootloader
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- '''
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+ [[introduction]]
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+ == Introduction
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+ *GRUB2* is the latest version of *GNU GRUB*, the _GRand Unified Bootloader_.
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+ A bootloader is the first software program that runs when a computer
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+ starts. It is responsible for loading and transferring control to the
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+ operating system kernel. In Fedora, the kernel is Linux. The kernel then initializes
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+ the rest of the operating system.
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- [IMPORTANT]
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- ======
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+ *GRUB2* is the follower of the previous version *GRUB* (version 0.9x). The original version is available under the name *GRUB Legacy*.
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- This page was automatically converted from https://fedoraproject.org/wiki/GRUB_2
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+ Since Fedora 16, *GRUB2* has been the default bootloader on x86 BIOS
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+ systems. For upgrades of BIOS systems, the default is also to install
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+ *GRUB2*, but you can opt to skip bootloader configuration entirely.
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- It is probably
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+ [[installing-grub-2-on-a-bios-system]]
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+ == Installing GRUB2 on a BIOS system
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- * Badly formatted
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- * Missing graphics and tables that do not convert well from mediawiki
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- * Out-of-date
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- * In need of other love
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+ Usually, *GRUB2* will be installed 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, if you want to update from an older or different bootloader, for instance. To install *GRUB2*:
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- Please fix it, remove this notice, and then add to `_topic_map.yml`
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+ . Install *GRUB2* software using the *dnf* package manager
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+ +
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+ ----
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+ $ sudo dnf install grub2
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+ ----
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- Pull requests accepted at https://pagure.io/fedora-docs/quick-docs
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+ [[Installing-grub-2-on-the-hard-disk-bios]]
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+ == Installing GRUB2 on the hard disk on BIOS systems
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- Once that is live, go to the original wiki page and add an `{{old}}`
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- tag, followed by a note like
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+ Installing the *GRUB2* software on your system does not change your bootloader configuration. In order to use *GRUB2* for loading the operating system, you have to install it on the hard disk. There are two possible options to install it:
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- ....
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- {{admon/note|This page has a new home!|
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- This wiki page is no longer maintained. Please find the up-to-date
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- version at: https://docs.fedoraproject.org/whatever-the-url
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- }}
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- ....
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+ . in the master boot record (MBR) of the hard disk
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+ . on an extra partition on the hard disk
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- ======
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+ *GRUB2* is able to load many operating systems, including Windows, so it is recommended to install it as the default bootloader in the MBR of the primary hard disk, usually the `sda` device.
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- '''
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+ .Before you start
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+ * Make sure you have installed the *GRUB2* software onto your system. See xref:installing-grub-2-on-a-system[Installing GRUB2 on your system] for more information.
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+ * To automatically collect information about your disks and operating systems installed on them, the `os-prober` package needs to be installed on your system.
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- [[introduction]]
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- Introduction
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- ------------
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-
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- GRUB 2 is the latest version of GNU GRUB, the GRand Unified Bootloader.
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- A bootloader is the first software program that runs when a computer
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- starts. It is responsible for loading and transferring control to the
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- operating system kernel, (Linux, in the case of Fedora). The kernel, in
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- turn, initializes the rest of the operating system.
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+ .Procedure
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- GRUB 2 has replaced what was formerly known as GRUB (i.e. version 0.9x),
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- which has, in turn, become GRUB Legacy.
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+ . List devices available on the system.
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+ +
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+ ----
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+ $ lsblk
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+ ----
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- Starting with Fedora 16, GRUB 2 is the default bootloader on x86 BIOS
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- systems. For upgrades of BIOS systems the default is also to install
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- GRUB 2, but you can opt to skip bootloader configuration entirely.
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+ . Identify the primary hard disk. Usually, it is the `sda` device.
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- [[tasks-common-issues]]
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- Tasks / Common issues
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- ---------------------
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+ . Install *GRUB2* in the MBR of the primary hard disk.
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+ +
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+ ----
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+ $ sudo grub2-install /dev/sda
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+ ----
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- [[updating-grub-2-configuration-on-bios-systems]]
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- Updating GRUB 2 configuration on BIOS systems
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- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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+ . Create a configuration file for *GRUB2*.
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+ +
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+ ----
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+ $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
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+ ----
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- The grub2 packages contain commands for installing a bootloader and for
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- creating a bootloader configuration file.
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+ .More information
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- grub2-install will install the bootloader - usually in the MBR, in free
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- unpartioned space, and as files in /boot. The bootloader is installed
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- with something like:
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+ * The `grub2-mkconfig` command will create a new configuration based on the currently
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+ running system. It collects information from the `/boot` partition (or directory), from the `/etc/default/grub` file, and the customizable scripts in `/etc/grub.d/`.
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+ * The configuration format has evolved over time, and a new configuration
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+ file might be slightly incompatible with the old bootloader. It is
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+ therefore a good idea to first run `grub2-install` whenever you would need
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+ to run `grub2-mkconfig`.
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+ * It is generally safe to directly edit `/boot/grub2/grub.cfg` in Fedora.
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+ *Grubby* in Fedora patches the configuration when a kernel update is
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+ performed and will try to not make any other changes than what is
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+ necessary. Manual changes might however be
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+ overwritten with `grub2-mkconfig` next time the system is upgraded with
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+ *Anaconda*. Customizations can be placed in `/etc/grub.d/40_custom` or
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+ `/boot/grub2/custom.cfg` files and will survive running the `grub2-mkconfig` command.
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- ....
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- grub2-install /dev/sda
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- ....
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+ [[installing-grub-2-configuration-on-uefi-system]]
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+ == Installing GRUB2 on a UEFI system
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- grub2-mkconfig will create a new configuration based on the currently
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- running system, what is found in /boot, what is set in
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- /etc/default/grub, and the customizable scripts in /etc/grub.d/ . A new
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- configuration file is created with:
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+ To install or fix *GRUB2* on a UEFI system on Fedora 18 or newer, you
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+ need to do three things:
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- ....
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- grub2-mkconfig -o /boot/grub2/grub.cfg
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- ....
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+ * create an EFI System Partition (ESP)
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+ * install the bootloader files
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+ * configure the *GRUB2* configuration
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- The configuration format has evolved over time, and a new configuration
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- file might be slightly incompatible with the old bootloader. It is
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- therefore a good idea to first run grub2-install whenever you would need
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- to run grub2-mkconfig.
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+ [[create-an-esp]]
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+ === Create an ESP
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- The Fedora installer, anaconda, will run these grub2 commands and there
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- is usually no reason to run them manually.
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+ UEFI firmware, in general, likes to boot from an _EFI System Partition_ on
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+ a disk with a GPT label.
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- It is generally safe to directly edit /boot/grub2/grub.cfg in Fedora.
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- Grubby in Fedora patches the configuration when a kernel update is
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- performed and will try to not make any other changes than what is
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- necessary. (Other distributions, in particular Debian and Debian-derived
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- distributions provide a software patch that adds an command which is
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- neither included nor needed in Fedora.) Manual changes might however be
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- overwritten with grub2-mkconfig next time the system is upgraded with
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- anaconda. Some customizations can be placed in /etc/grub.d/40_custom or
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- /boot/grub2/custom.cfg and will survive running grub2-mkconfig.
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+ .Before you start
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- [[updating-grub-2-configuration-on-uefi-systems]]
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- Updating GRUB 2 configuration on UEFI systems
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- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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+ . Learn how to create partitions using `gdisk`.
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- To install or fix GRUB 2 on a UEFI system on Fedora 18 or newer, you
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- need to do four things:
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+ .Procedure
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- [[create-an-esp]]
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- Create an ESP
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- ^^^^^^^^^^^^^
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+ . List available block devices to find a place to create your ESP.
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+ +
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+ ----
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+ $ lsblk
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+ ----
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- UEFI firmware, in general, likes to boot from an EFI System Partition on
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- a disk with a GPT label. In `gdisk`, it looks something like this:
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+ . Create at least a 128 MiB disk partition using a GPT label on the primary hard disk.
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+ +
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+ ----
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+ $ sudo gdisk /dev/sda
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+ ----
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- ....
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- Number Start (sector) End (sector) Size Code Name
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- 1 2048 264191 128.0 MiB EF00 EFI System
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- ....
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+ . Format the partition with the _FAT32_ file system.
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+ +
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+ ----
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+ $ sudo mkfs.vfat /dev/sda1
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+ ----
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- That partition should be formatted as FAT. If in doubt, FAT32 is a good
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- dialect of FAT to choose.
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+ . Mount the partition to `/boot/efi` mount point.
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+ +
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+ ----
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+ $ sudo mount /dev/sda1 /boot/efi
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+ ----
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- Fedora expects this partition to be mounted at `/boot/efi`.
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[[install-the-bootloader-files]]
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- Install the bootloader files
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- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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+ === Install the bootloader files
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- If you don't already have the relevant packages installed, do for Fedora
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- 22 and later versions with link:dnf[DNF] or with YUM for older Fedora
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- releases:
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+ In order to use *GRUB2* with on the UEFI systems, you need to install appropriate packages:
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- ....
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- dnf install grub2-efi grub2-efi-modules shim
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- yum install grub2-efi grub2-efi-modules shim
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- ....
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+ .Before you start
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- If you do, then try:
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+ . Mount the `/boot/efi` mount point. See xref:create-an-esp[Create an ESP] to create it.
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- ....
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- dnf reinstall grub2-efi grub2-efi-modules shim
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- yum reinstall grub2-efi grub2-efi-modules shim
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- ....
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+ .Procedure
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+
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+ . Install the necessary packages.
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+ +
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+ ----
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+ dnf install grub2-efi grub2-efi-modules shim
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+ ----
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- instead.
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+ . If they are already installed, reinstall them.
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+ +
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+ ----
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+ dnf reinstall grub2-efi grub2-efi-modules shim
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+ ----
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- Make sure that /boot/efi is mounted when you do this.
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+ .More information
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- This installs the signed shim and the GRUB 2 binary.
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+ * This installs the signed shim and the *GRUB2* binary.
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[[create-a-grub-2-configuration]]
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- Create a GRUB 2 configuration
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- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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+ === Create a GRUB2 configuration
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- Under EFI, GRUB 2 looks for its configuration in
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+ Under EFI, *GRUB2* looks for its configuration in
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`/boot/efi/EFI/fedora/grub.cfg`. For newly installed kernels to work,
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`grubby` expects `/etc/grub2-efi.cfg` to be a symlink to the real
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- grub.cfg (i.e. `/boot/efi/EFI/fedora/grub.cfg`).
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+ grub.cfg (for example `/boot/efi/EFI/fedora/grub.cfg`).
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- If you already have a grub 2 EFI config file, you should be okay. If
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- not, grub2-mkconfig can help, but your mileage may vary.
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+ If you already have a *GRUB2* EFI config file, you do not need to do anything else. Otherwise, you can try to create the configuration file using the `grub2-mkconfig` command.
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- ` grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg`
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+ ----
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+ $ sudo grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
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+ ----
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- [[create-a-boot-menu-entry]]
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- Create a boot menu entry
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- ^^^^^^^^^^^^^^^^^^^^^^^^
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+ [[solve-problems-with-uefi-bootloader]]
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+ === Solve problems with UEFI bootloader.
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- TL;DR: This should happen automatically. If it doesn't, read on.
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+ [[adding-the-boot-menu-entries]]
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+ ==== Adding the boot menu entries
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When you power on your system, your firmware will look for EFI variables
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- that tell it how to boot. If you're already booted in EFI mode and EFI
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+ that tell it how to boot. If you are already booted in EFI mode and EFI
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runtime services are working correctly, you can configure your boot menu
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- with `efibootmgr`. If not, you'll have to bootstrap the process.
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+ with `efibootmgr`. If not, you will have to bootstrap the process.
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Fortunately, `shim` can help you bootstrap. The EFI program
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`/boot/efi/EFI/BOOT/fallback.efi` will look for files called `BOOT.CSV`
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- in your ESP and will add boot entries corresponding to them, *if such
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- entries do not already appear to exist*. `shim` provides a `BOOT.CSV`
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- file that will add an entry for `grub2-efi` for you. So just using the
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- EFI Shell to invoke `fallback.efi` should do the trick. You can do this
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+ in your ESP and will add boot entries corresponding to them. The `shim` command
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+ provides a `BOOT.CSV` file that will add an entry for `grub2-efi` for you.
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+
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+ Using the *EFI Shell* to invoke `fallback.efi` should work for you. You can do this
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with commands like:
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- ....
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+ ----
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> fs0:
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> cd EFI\BOOT
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> fallback.efi
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- ....
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+ ----
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If you have no boot entries at all, then just booting off your disk in
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UEFI mode should automatically invoke `/boot/efi/EFI/BOOT/BOOTX64.EFI`,
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@@ -193,285 +199,357 @@
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them or to modify `BOOT.CSV` to create new entries with different names.
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[[adding-other-operating-systems-to-the-grub-2-menu]]
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- Adding Other operating systems to the GRUB 2 menu
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- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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+ ==== Adding Other operating systems to the *GRUB2* menu
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- grub2-mkconfig will add entries for other operating systems it can find.
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- That will be done based on the output of the os-prober tool.
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+ The `grub2-mkconfig` command will add entries for all operating systems it can find.
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+ For the command to work, you have to have installed the *os-prober* tool that is provided by the `os-prober` package.
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- That might however not work so well, especially not for booting other
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- Linux operating systems, and especially not on UEFI systems. See
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- http://www.gnu.org/software/grub/manual/grub.html#Multi_002dboot-manual-config
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- .
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+ Unfortunately, problem sometimes can 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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[[setting-default-entry]]
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- Setting default entry
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- ~~~~~~~~~~~~~~~~~~~~~
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+ ==== Setting default entry
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- Due to `grub2-mkconfig` (and os-prober) we cannot predict the order of
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+ Due to `grub2-mkconfig` (and *os-prober*) we cannot predict the order of
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the entries in `/boot/grub2/grub.cfg`, so we set the default by
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name/title instead.
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- Open `/etc/default/grub` and ensure this line exists:
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+ .Before you start
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- ....
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+ . Open `/etc/default/grub` and make sure these lines exist in the file.
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+ +
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+ ----
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GRUB_DEFAULT=saved
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- ....
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-
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- and ensure this line not exists:
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-
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- ....
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- GRUB_SAVEDEFAULT=true
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- ....
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-
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- or ensure this line exists:
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-
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- ....
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GRUB_SAVEDEFAULT=false
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- ....
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-
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- Apply the change to `grub.cfg` by running:
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-
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- ....
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- grub2-mkconfig -o /boot/grub2/grub.cfg
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- ....
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-
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- Now list all possible menu entries
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-
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- ....
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- grep -P "submenu|^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
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- ....
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-
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- Now set the desired default menu entry
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-
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- ....
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- grub2-set-default "<submenu title><menu entry title>"
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- ....
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-
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- Verify the default menu entry
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-
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- ....
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- grub2-editenv list
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- ....
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-
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- If you understand the risks involved and still want to directly modify
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- /boot/grub2/grub.cfg, here's how you can do it:
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-
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- Edit /boot/grub2/grub.cfg, and change the line
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-
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- ....
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- set default="0"
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- ....
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-
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- to
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-
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- ....
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+ ----
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+
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+ . Apply the changes to `grub.cfg` by running.
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+ +
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+ ----
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+ $sudo grub2-mkconfig -o /boot/grub2/grub.cfg
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+ ----
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+
|
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+ .Procedure
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+
|
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+ . List all possible menu entries.
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+ +
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+ ----
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+ $sudo grep -P "submenu|^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
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+ ----
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+
|
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+ . Set the desired default menu entry
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+ +
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+ ----
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+ $sudo grub2-set-default "<submenu title><menu entry title>"
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+ ----
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+
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+ . Verify the default menu entry
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+ +
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+ ----
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+ $sudo grub2-editenv list
|
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+ ----
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+
|
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+ .More information
|
| |
+ If you understand the risks involved, you can manually modify the
|
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+ `/boot/grub2/grub.cfg` file. In that case, set the number of the default operating system using the `set default` variable.
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+
|
| |
+ For example:
|
| |
+ ----
|
| |
set default="5"
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- [[encountering-the-dreaded-grub-2-boot-prompt]]
|
| |
- Encountering the dreaded GRUB 2 boot prompt
|
| |
- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
| |
|
| |
- If improperly configured, GRUB 2 may fail to load and subsequently drop
|
| |
+ [[additional-scenario]]
|
| |
+ == Additional Scenarios
|
| |
+
|
| |
+ [[restoring-bootloader-using-live-disk]]
|
| |
+ === Restoring the bootloader using the 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
|
| |
+ ----
|
| |
+
|
| |
+ . Reinstall *GRUB2* into the MBR of the primary hard disk.
|
| |
+ +
|
| |
+ ----
|
| |
+ $ sudo grub2-install --no-floppy --recheck /dev/sda
|
| |
+ ----
|
| |
+
|
| |
+ . Recreate the *GRUB2* configuration files.
|
| |
+ +
|
| |
+ ----
|
| |
+ $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
|
| |
+ ----
|
| |
+
|
| |
+ . Exit this temporary root filesystem.
|
| |
+ +
|
| |
+ ----
|
| |
+ $ exit
|
| |
+ ----
|
| |
+
|
| |
+ . Your bootloader should be now restored. Reboot your computer to boot into your normal system.
|
| |
+ +
|
| |
+ ----
|
| |
+ $ sudo systemctl reboot
|
| |
+ ----
|
| |
+
|
| |
+ [[using-the-grub-2-boot-prompt]]
|
| |
+ ==== Using the GRUB2 boot prompt
|
| |
+
|
| |
+ If improperly configured, *GRUB2* may fail to load and subsequently drop
|
| |
to a boot prompt. To address this issue, proceed as follows:
|
| |
|
| |
- \0. Load the XFS and LVM modules
|
| |
-
|
| |
- ....
|
| |
+ . Load the XFS and LVM modules
|
| |
+ +
|
| |
+ ----
|
| |
insmod xfs
|
| |
insmod lvm
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- \1. List the drives which GRUB 2 sees:
|
| |
-
|
| |
- ....
|
| |
+ . List the drives which *GRUB2* sees:
|
| |
+ +
|
| |
+ ----
|
| |
grub2> ls
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- \2. The output for a dos partition table /dev/sda with three partitons
|
| |
+ . 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)
|
| |
- ....
|
| |
-
|
| |
- \3. While the output for a gpt partition table /dev/sda with four
|
| |
- partitions will look something like this:
|
| |
-
|
| |
- ....
|
| |
+ ----
|
| |
+ +
|
| |
+ 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)
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- \4. With this information you can now probe each partition of the drive
|
| |
- and locate your vmlinuz and initramfs files:
|
| |
-
|
| |
- ....
|
| |
+ . Probe each partition of the drive and locate your `vmlinuz` and `initramfs` files.
|
| |
+ +
|
| |
+ ----
|
| |
ls (hd0,1)/
|
| |
- ....
|
| |
-
|
| |
- Will list the files on /dev/sda1. If this partition contains /boot, the
|
| |
- output will show the full name of vmlinuz and initramfs.
|
| |
-
|
| |
- \5. Armed with the location and full name of vmlinuz and initramfs you
|
| |
- can now boot your system.
|
| |
-
|
| |
- 5a. Declare your root partition:
|
| |
+ ----
|
| |
+ +
|
| |
+ 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)
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- 5b. Declare the kernel you wish to use:
|
| |
-
|
| |
- ....
|
| |
+ . 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 have need of them
|
| |
# NOTE : change the numbers to match your system
|
| |
- ....
|
| |
-
|
| |
- 5c. Declare the initrd to use:
|
| |
+ ----
|
| |
|
| |
- ....
|
| |
-
|
| |
+ . Set the desired `initrd`.
|
| |
+ +
|
| |
+ ----
|
| |
grub> initrd (hd0,1)/initramfs-3.0.0-1.fc16.i686.img
|
| |
# NOTE : change the numbers to match your system
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- 5d. Instruct GRUB 2 to boot the chosen files:
|
| |
-
|
| |
- ....
|
| |
+ . Boot with the selected settings.
|
| |
+ +
|
| |
+ ----
|
| |
grub> boot
|
| |
- ....
|
| |
-
|
| |
- \6. After boot, open a terminal.
|
| |
+ ----
|
| |
|
| |
- \7. Issue the grub2-mkconfig command to re-create the grub.cfg file
|
| |
- grub2 needed to boot your system:
|
| |
+ . When the system starts, open a terminal.
|
| |
|
| |
- ....
|
| |
+ . Enter the `grub2-mkconfig` command to re-create the `grub.cfg` file to enable *GRUB2* to boot your system.
|
| |
+ +
|
| |
+ ----
|
| |
grub2-mkconfig -o /boot/grub2/grub.cfg
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- \8. Issue the grub2-install command to install grub2 to your hard drive
|
| |
- and make use of your config:
|
| |
-
|
| |
- ....
|
| |
+ . Enter the `grub2-install` command to install *GRUB2* to your hard disk to use of your config file.
|
| |
+ +
|
| |
+ ----
|
| |
grub2-install --boot-directory=/boot /dev/sda
|
| |
# Note: your drive may have another device name. Check for it with mount command output.
|
| |
- ....
|
| |
-
|
| |
- [[additional-scenario]]
|
| |
- Additional Scenario
|
| |
- ~~~~~~~~~~~~~~~~~~~
|
| |
+ ----
|
| |
|
| |
+ [[booting-with-configfile-on-different-partition]]
|
| |
+ === Booting the system using a configuration file on a different partition.
|
| |
It's also possible to boot into a _configfile_ that's located on another
|
| |
partition. If the user is faced with such a scenario, as is often the
|
| |
case with multi-boot systems containing Ubuntu and Fedora, the following
|
| |
- steps in the grub rescue shell might become useful to know:
|
| |
+ steps in the *GRUB2* rescue shell might become useful to know:
|
| |
+
|
| |
+ .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
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- Where, *hd0,msdos1* is the pertinent _boot_ partition, which holds the
|
| |
- grub.cfg file.
|
| |
+ .More information
|
| |
+ The *hd0,msdos1* line shows the pertinent _boot_ partition, which holds the
|
| |
+ `grub.cfg` file.
|
| |
|
| |
- [[other-grub-2-issues]]
|
| |
- Other GRUB 2 issues
|
| |
- ~~~~~~~~~~~~~~~~~~~
|
| |
+ [[absent-floppy-disk]]
|
| |
+ === Dealing with the "Absent Floppy Disk" Error
|
| |
|
| |
- ''' Absent Floppy Disk ''': It has been reported by some users that GRUB
|
| |
- 2 may fail to install on a partition's boot sector if the computer
|
| |
- floppy controller is activated in BIOS without an actual floppy disk
|
| |
- drive being present. A possible workaround is to run (post OS install)
|
| |
- from rescue mode:
|
| |
+ 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 install *GRUB2* with the `--no-floppy` option:
|
| |
+
|
| |
+ ----
|
| |
grub2-install <target device> --no-floppy
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
[[setting-a-password-for-interactive-edit-mode]]
|
| |
- Setting a password for interactive edit mode
|
| |
- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
| |
+ === Setting a password for interactive edit mode
|
| |
+
|
| |
+ If you wish to password-protect the *GRUB2* interactive edit mode
|
| |
+ without forcing users to enter a password to boot the computer, use this procedure.
|
| |
|
| |
- If you wish to password-protect GRUB2's interactive edit mode *but* you
|
| |
- do not want to require users to enter a password to do a plain, simple,
|
| |
- ordinary boot, create /etc/grub.d/01_users with the following lines:
|
| |
+ .Procedure
|
| |
|
| |
- ....
|
| |
+ . Create the `/etc/grub.d/01_users` file.
|
| |
+ +
|
| |
+ ----
|
| |
cat << EOF
|
| |
set superusers="root"
|
| |
export superusers
|
| |
password root secret
|
| |
EOF
|
| |
- ....
|
| |
+ ----
|
| |
|
| |
- To apply your changes run:
|
| |
-
|
| |
- ....
|
| |
+ . Apply your changes.
|
| |
+ +
|
| |
+ ----
|
| |
grub2-mkconfig -o /boot/grub2/grub.cfg
|
| |
- ....
|
| |
+ ----
|
| |
+
|
| |
+ .More information
|
| |
|
| |
- You can encrypt the password by using pbkdf2. Use grub2-mkpasswd-pbkdf2
|
| |
+ 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].
|
| |
|
| |
- Starting from atleast Fedora 21, the `--md5pass` kickstart option must
|
| |
- be set using output from grub2-mkpasswd-pbkdf2.
|
| |
+ [NOTE]
|
| |
+ ====
|
| |
+ Starting from Fedora 21, the `--md5pass` kickstart option must
|
| |
+ be set using output from the `grub2-mkpasswd-pbkdf2` command.
|
| |
+ ====
|
| |
|
| |
[[using-old-graphics-modes-in-bootloader]]
|
| |
- Using old graphics modes in bootloader
|
| |
- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
| |
+ === Using old graphics modes in bootloader
|
| |
|
| |
Terminal device is chosen with GRUB_TERMINAL; additional quote from
|
| |
http://www.gnu.org/software/grub/manual/grub.html#Simple-configuration
|
| |
|
| |
- 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).
|
| |
+ 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.
|
| |
|
| |
- The default in Fedora is gfxterm and to get the legacy graphics modes
|
| |
- you need to set GRUB_TERMINAL to right variable from the description
|
| |
- above in /etc/default/grub
|
| |
+ The default in Fedora is `gfxterm` and to get the legacy graphics modes
|
| |
+ you need to set GRUB_TERMINAL to the right variable from the description
|
| |
+ above in `/etc/default/grub`.
|
| |
|
| |
- [[enable-serial-console-in-grub]]
|
| |
- Enable Serial Console in Grub
|
| |
- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
| |
+ [[enabling-serial-console-in-grub]]
|
| |
+ === Enabling Serial Console in GRUB2
|
| |
|
| |
- To enable Serial console in grub add the following entry's to
|
| |
- /etc/default/grub
|
| |
+ To enable Serial console in grub:
|
| |
|
| |
- ( Adjust baudrate/parity/bits/flow control to fit your environment and
|
| |
- cables)
|
| |
-
|
| |
- ....
|
| |
+ . Add the following entry to `/etc/default/grub`. Adjust `baudrate`, `parity`, `bits`, and `flow` controls to fit your environment and cables.
|
| |
+ +
|
| |
+ ----
|
| |
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"
|
| |
- ....
|
| |
-
|
| |
- And re-generate grub
|
| |
+ ----
|
| |
|
| |
+ . Re-generate the GRUB2 config file.
|
| |
+ +
|
| |
`grub2-mkconfig -o /boot/grub2/grub.cfg`
|
| |
|
| |
[[further-reading]]
|
| |
- Further Reading
|
| |
- ---------------
|
| |
+ == Further Reading
|
| |
|
| |
* http://www.gnu.org/software/grub/manual/grub.html
|
| |
* Features/Grub2
|
| |
lruzicka
commented 6 years ago
Fix markup.
Edit procedures.
Add info on restoring bootloader.