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Fedora 23

Multiboot Guide

Booting Fedora and other operating systems.

Fedora Documentation Project

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Abstract
The Fedora Multiboot Guide explains using Fedora to enable booting of one or more additional operating systems. The Guide covers the basic principles of GRUB, Fedora's bootloader, and demonstrates configuration of GRUB on both BIOS and UEFI systems.

1. Introduction
2. Bootloader Basics
3. Frequently Asked Questions
4. Is your system UEFI or BIOS?
5. Making Room for Fedora
5.1. Using the Fedora Installer to resize partitions
5.2. Resizing an NTFS filesystem the command line
6. The GRUB Bootloader
6.1. GRUB Basics
6.2. Changing GRUB entries at boot
6.3. Recreating GRUB
6.4. Configuring the GRUB Bootloader
7. Multiboot on BIOS Systems
7.1. BIOS Basics
8. Multiboot on UEFI Systems
8.1. UEFI Basics
8.2. Booting on Windows Systems
8.3. Booting on Apple systems
9. Boot Options
A. Common Operations
A.1. Setting up a chroot from a live image
B. Revision History
Index

1. Introduction

Fedora 21 can be used as the only operating system on your computer, or you can dual boot Fedora with another operating system. Fedora can enable selection of other options at boot, often with little to no user configuration. Systems that can boot more than two operating systems are referred to as multiboot systems.
Installing Fedora on a system where another operating system is installed requires unallocated drive space. Section 5, “Making Room for Fedora” explains options for creating this free space.
When your computer starts, it first performs self tests, then loads a bootloader, GRUB. GRUB provides a menu so you can select the Fedora kernel or other operating system you would like to boot, and GRUB's configuration file stores the options and settings required for initial booting of the selected operating system. Read Section 6, “The GRUB Bootloader” for more information on GRUB.
Changing Fedora's boot options can be helpful, especially when troubleshooting. Section 6.4, “Configuring the GRUB Bootloader” explains how to change these options once or permanently.
The system's firmware allows basic configuration, performs initial startup, initializes hardware, and brings up the bootloader. Until recently, this firmware was referred to as the BIOS, or Basic Input Output System, which is described in Section 2, “Bootloader Basics”. Newer systems, such as those sold with Windows 8, use a newer type called UEFI or Universal Extensible Firmware Interface, which is described in Section 2, “Bootloader Basics”
In most cases, the Fedora installer will recognize other operating systems on your computer and create boot menu entries for them. If an operating system such as Windows is installed after Fedora, GRUB may be overwritten and require reinstallation. Some circumstances, such as missing menu entries, require refreshing of the menu entries. These tasks are explained in Section 7, “Multiboot on BIOS Systems” or Section 8, “Multiboot on UEFI Systems”
The Guide also covers concerns regarding booting of specific operating systems. For information regarding booting of Fedora with Windows 8, refer to Section 8.2, “Booting on Windows Systems”. To learn about using Fedora on Apple hardware, read Section 8.3, “Booting on Apple systems”

Using Root Safely

Many of the procedures in this guide involve editing of files or execution of commands that can only be performed as root. The root account should be used with educated caution and only when required. Your system can break or fail to boot if the account is misused.
If your normal user account is configured as an administrator, you can use sudo to enter your user password and execute privileged commands:
[fedorauser@localhost ~]$ sudo <command>
[sudo] password for fedorauser:
You can also open a root shell using the root password su. The hyphen ( - ) in the example is important because it ensures that you will work in a root environment, and not act on normal user files with root privileges.
[fedorauser@localhost ~]$ su -
Password:
[root@localhost ~]#
The root prompt is always a hash ( # ) and a normal user prompt is always a dollar sign ( $ ). Example commands in this guide will include one of these prompts to show the privileges required for the action.
To keep your system healthy and safe, do not execute user applications as root or log into a desktop environment as root.

2. Bootloader Basics

To boot a modern operating system, a computer must identify the kernel, storage, and various options at the time of booting. Software called a bootloader keeps track of these parameters, manages settings for different operating systems, and loads the kernel.

Bootloaders on BIOS systems

Historically, bootloaders have been installed into the first part of a drive, known as the Master Boot Record (MBR) or Boot Sector. The computer's firmware, or BIOS, would check the boot sector for bootable code on startup, and load whatever it found. As bootloaders became more complex, and therefore required more space, the MBR came to contain only a pointer to the second stage of the bootloader.
The second stage of the bootloader performs the actual work. Because the BIOS does not know how to open and read from filesystems, the bootloader finds the operating system, presents a menu, interacts with the user as required, and launches the OS. It was installed in the part of the drive between the MBR and the beginning of the first filesystem, known as the MBR Gap. Less featureful bootloaders could also be installed in the gap between the start of the partition and the beginning of the partition's filesystem, but because this can damage the filesystem if the gap is too small the practice is no longer supported.
BIOS is short for Basic Input Output System, and the software is indeed very simple. BIOS systems had a number of technical limitations, such as being unable to boot from disks larger than 2 TB and extremely limited interfaces. GUID Partition Table (GPT) partitioning schemes also came with larger drives, overcoming the MBR partitioning scheme's 4 partition limit. To overcome these issues and add new features, a newer firmware implementation was developed, called the Unified Extensible Firmware Interface (UEFI).

Bootloaders on EFI systems

Instead of reading the bootloader from the drive, UEFI systems store information about available bootloaders right on the system firmware. Each boot entry is persistently stored on the firmware, and describes the location of the entry's bootloader.
The bootloaders themselves, and sometimes small applications such as memory testing utilites, are stored on the UEFI system partition. This partition contains a FAT filesystem, has a standardized partition identifier, and is mounted at /boot/efi. Each operating system places files required for booting in a dedicated directory of this partition, and the boot entry in the firmware points to these files. UEFI systems will often also support BIOS style booting for compatibility reasons, using a feature called the Compatibility Support Module (CSM).

Bootloader data

On Linux systems, the data used by the bootloader is traditionally contained in a boot partition, mounted at and known as /boot. The boot partition contains the kernel, a read only filesystem that holds tools used by the kernel during bootup, called an initramfs, and files for the menus and for the bootloader itself. These files were traditionally placed on a different partition because the bootloader did not support complex storage arrangements, and could not read the kernel and initramfs from them. Because a simple, separate boot also allows for easier disaster recovery, the practice has continued to this day.
Fedora supports both UEFI and BIOS systems, using the GRUB bootloader, which is short for GNU GRand Unified Bootloader. GRUB provides a boot menu and support for many filesystems, as well as software for scanning the system for available operating systems and adding them to the menu.

3. Frequently Asked Questions

Q: Can I install Fedora on my computer, and keep Windows?
Q: Can I access my files from Windows from Fedora? What about accessing my Fedora files from Windows?
Q: Can I replace my unsupported Windows XP installation with Fedora?
Q: Can I install my favorite software on Fedora?
Q: Should I install Windows first, or Fedora?
Q: Can I have Windows installed in UEFI mode (the default for Windows 8 systems) and disable it to install Fedora?
Q: Can I use universal USB creation tools to create Fedora installation media?
Q: The Fedora installer says I don't have enough free space, but Windows says my C: drive has plenty. What's going on?
Can I install Fedora on my computer, and keep Windows?
Yes! Fedora can coexist with Windows, other Linux distributions, and more. Fedora provides a menu that lets you choose the operating system to use when you turn on your computer.
Can I access my files from Windows from Fedora? What about accessing my Fedora files from Windows?
You can easily access your Windows files from Fedora. The Files application in Fedora Workstation, and most other graphical file browsers, will show Windows NTFS volumes for you to browse.
Unlike Fedora, Windows does not have native support for most filesystems. There are third party drivers available that allow Windows to read some filesystems, like ext3 and ext4. Windows does not currently support virtual block devices such as LVM, which is used for Fedora installations unless you specify otherwise.
Can I replace my unsupported Windows XP installation with Fedora?
Of course! Fedora releases a new version roughly every six months, so keeping up with Fedora means you'll have a secure operating system with the latest open source software.
If your computer came with Windows XP, try out alternative desktop environments from https://spins.fedoraproject.org. Fedora has something to offer for older, less powerful computers that might be more suitable for you.
Can I install my favorite software on Fedora?
Fedora is more than just an operating system, it's a robust ecosystem of open source software. Word processing applications, spreadsheet programs, games, music and movie players, image viewers and editors, and email clients are just the beginning of the software Fedora provides.
Some of the software will be the same as on Windows, like Firefox. Some, like LibreOffice Writer or Calc, do the job you're looking for in a familiar way. Fedora's repositories offer solutions for almost every computing task, but it might not do it with the same program you're used to.
Should I install Windows first, or Fedora?
It's best to install Windows first. Fedora should detect your Windows installation, and set up a bootloader entry for it. Windows will overwrite the Fedora bootloader, and does not set up a menu option for Fedora.
On newer computers, this usually isn't as important as it was in the past. The system doesn't need to rely on the bootloader from one operating system or another, because they have information about each installed operating system stored in the UEFI firmware. You can simply choose your OS from the system boot menu.
Can I have Windows installed in UEFI mode (the default for Windows 8 systems) and disable it to install Fedora?
No, you should not do that. UEFI's job is to boot operating systems, and if you disable that, you will also disable the ability to boot OSes that need it.
You should be consistent about firmware settings when multibooting. If you have a UEFI system, use it for every OS you install. Fedora supports UEFI systems, with or without SecureBoot. If you use backwards compatibility settings to emulate BIOS installations, you should do so for every OS you install.
Can I use universal USB creation tools to create Fedora installation media?
In short, no.
To fully answer that, you have to understand what these tools do. In times past, Linux distributions produced ISO images in a format that made them work when burned to an optical disc. The same format doesn't work when the image is directly written to a USB drives, so tools were created to modify the images for use on USB sticks. Typically, this involved transferring the contents of the image to the USB drive, then installing a syslinux bootloader to the drive and configuring it to boot the drive's new contents.
Today, Fedora images are created in a hybrid format that's directly usable as an optical disk or USB disk, for both legacy and UEFI systems. A syslinux bootloader alone isn't compatible with UEFI booting. When the universal installation tools replace the hybrid booting configuration with syslinux, the image can't be used on UEFI systems. You end up with a USB drive that's only bootable in legacy mode, which conflicts with dual booting of other operating systems installed in UEFI mode, such as any laptop preinstalled with Windows 8.
For best results, follow the instructions in the Fedora Installation Guide for a direct write method of creating USB media.
The Fedora installer says I don't have enough free space, but Windows says my C: drive has plenty. What's going on?
Fedora needs it's own space, it cannot use free space on C:. You can use the installer to resize existing partitions and make room for Fedora.

4. Is your system UEFI or BIOS?

Because commands and file locations differ between BIOS and UEFI systems, it is important to identify which you have before attempting advanced boot configuration.
Identifying a BIOS system
  • Older computers are more likely to use BIOS. UEFI systems did not become commonplace until after 2010.
  • 32 bit systems are almost always BIOS. ( UEFI booting of 32 bit systems is not supported by Fedora )
  • Your computer originally shipped with Windows Vista or XP.
  • The computer's manual and the system setup menu do not mention UEFI, EFI, or SecureBoot.

The term BIOS is still used with UEFI systems

Because BIOS systems have been around for so long, the term BIOS is often used to describe UEFI systems as well. Manufacturers might list system firmware updates as BIOS updates or provide directions to enter the BIOS setup menu. The word has come to represent the pre-OS menu on your computer as much as the actual software, but your system may still be UEFI capable.
To avoid confusion, this guide uses the term firmware when describing interactions with BIOS or UEFI menus.
Identifying a UEFI system
  • Newer systems are more likely to use UEFI. If you bought your computer new in 2013 or after, it probably has UEFI.
  • Your computer shipped with Windows 8. The terms of service for manufacturers to distribute computers with Windows 8 require SecureBoot, a UEFI feature.
  • Your system setup menu has a graphical interface or mouse support. UEFI menus can be more elaborate.
  • The system's boot menu gives you the option of booting media via UEFI, or has boot options describing operating systems instead of just physical drives. The boot order menu might look like this:
    UEFI: Generic USB Stick
    Generic USB Stick
    UEFI: DVD-RW Drive
    DVD-RW Drive
    Fedora
    Windows
    

Be Consistent!

Be consistent with your booting methods when using multiple operating systems. If Windows is installed with UEFI, do not install Fedora in legacy BIOS compatibility mode. Installing all of your operating systems as either UEFI or BIOS booting will ensure that you can boot them all.

5. Making Room for Fedora

Fedora requires a volume of unallocated storage space for installation. To make room for Fedora, both the existing filesystem and the partition it resides on must be resized.

Be cautious when resizing!

Resizing partitions and filesystems is always a potentially destructive endeavor. While the methods described in this section are consistently reliable when properly executed, you should always be prepared for problems.
Before installing a new operating system on your computer, make sure you have current backups of any crucial data.
The advanced methods described in this section offer a greater degree of flexibility and control, but are more difficult to implement. You should resize partitions using the original operating system's native utilities, or using the Fedora installer, unless you are confident that you understand the advanced methods.

5.1. Using the Fedora Installer to resize partitions

The Fedora installer provides a guided graphical method for resizing partitions and reclaiming space. This method is simpler and easier than the others discussed in this section. For most simple dual boot situations, using the installer to reclaim space will be the most expedient and foolproof method.
Resizing partitions with the Fedora installer is covered in the Fedora Installation Guide

5.2. Resizing an NTFS filesystem the command line

This section explains using tools provided by Fedora to resize an NTFS partition. A terminal window from a liveCD can be used.

Disable Windows fast reboot feature!

Newer versions of Windows use a strategy of suspending some system processes to disk to speed startup times. Modifying a filesystem in this state can corrupt or damage the data, so the linux NTFS drivers will not mount it. If the filesystem were to be mounted, the cached view if the files may differ from the changes you made in Fedora, with the most likely result of loosing your changes - or worse.
Before attempting any operation on an NTFS volume from Fedora, make sure you have disabled this feature in Windows.
Procedure 1.  Selecting and resizing a partition.
  1. Show available filesystems:
    # blkid
    /dev/sda1: SEC_TYPE="msdos" UUID="32AE-E651" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="0315942d-8c2c-414f-a560-cfa499494a72" 
    /dev/sda2: UUID="593153ae-2b67-4a5b-9efa-fa3954953abd" TYPE="ext4" PARTUUID="68cadad8-6de2-4ef7-96ff-f58e5114fdcc" 
    /dev/sda3: UUID="P2xKTQ-aQWG-z2Uv-jSw5-kkUK-SN5Q-cNf3PI" TYPE="LVM2_member" PARTUUID="7ba7ed40-b43f-4e71-b83e-51629bf7db47" 
    /dev/sda5: UUID="44B6BAD1B6BAC2AA" TYPE="ntfs" PARTUUID="9c62d1dc-dedd-4d4c-9728-5f2ef69f2b42" 
    
  2. ntfs partitions indicate the existing Windows installation. Examine the partitions on the /dev/sda drive.
    # parted /dev/sda print
    Model: ATA ST9320328CS (scsi)
    Disk /dev/sda: 320GB
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt
    Disk Flags: pmbr_boot
    
    Number  Start   End    Size    File system  Name                          Flags
     1      1049kB  211MB  210MB   fat16        EFI System Partition          boot
     2      211MB   735MB  524MB   ext4
     3      735MB   119GB  118GB
     4      119GB   119GB  134MB                Microsoft reserved partition  msftres
     5      119GB   215GB  96.2GB  ntfs
    
  3. Partition number 5 is a large filesystem, and probably has some free space to share. Check how much of that space is in use.
    # ntfsresize --info /dev/sda5
    ntfsresize v2013.1.13 (libntfs-3g)
    Device name        : /dev/sda5
    NTFS volume version: 3.1
    Cluster size       : 4096 bytes
    Current volume size: 96234107392 bytes (96235 MB)
    Current device size: 96234110976 bytes (96235 MB)
    Checking filesystem consistency ...
    100.00 percent completed
    Accounting clusters ...
    Space in use       : 29222 MB (30.4%)
    Collecting resizing constraints ...
    You might resize at 29221265408 bytes or 29222 MB (freeing 67013 MB).
    Please make a test run using both the -n and -s options before real resizing!
    
  4. Resize the filesystem. Make sure to balance the available space, despite the suggestion from ntfsresize to shrink to the bare minimum. A very full filesystem can cause problems for any operating system.
    # ntfsresize --size 40G /dev/sda5
    ntfsresize v2013.1.13 (libntfs-3g)
    Device name        : /dev/sda5
    NTFS volume version: 3.1
    Cluster size       : 4096 bytes
    Current volume size: 96234107392 bytes (96235 MB)
    Current device size: 96234110976 bytes (96235 MB)
    New volume size    : 39999996416 bytes (40000 MB)
    Checking filesystem consistency ...
    100.00 percent completed
    Accounting clusters ...
    Space in use       : 29222 MB (30.4%)
    Collecting resizing constraints ...
    Needed relocations : 0 (0 MB)
    WARNING: Every sanity check passed and only the dangerous operations left.
    Make sure that important data has been backed up! Power outage or computer
    crash may result major data loss!
    Are you sure you want to proceed (y/[n])? y
    Schedule chkdsk for NTFS consistency check at Windows boot time ...
    Resetting $LogFile ... (this might take a while)
    Updating $BadClust file ...
    Updating $Bitmap file ...
    Updating Boot record ...
    Syncing device ...
    Successfully resized NTFS on device '/dev/sda5'.
    You can go on to shrink the device for example with Linux fdisk.
    IMPORTANT: When recreating the partition, make sure that you
      1)  create it at the same disk sector (use sector as the unit!)
      2)  create it with the same partition type (usually 7, HPFS/NTFS)
      3)  do not make it smaller than the new NTFS filesystem size
      4)  set the bootable flag for the partition if it existed before
    Otherwise you won't be able to access NTFS or can't boot from the disk!
    If you make a mistake and don't have a partition table backup then you
    can recover the partition table by TestDisk or Parted's rescue mode.        
    
Procedure 2. Resizing the partition
  1. To make sure that the partition is recreated accurately, work using sectors as units instead of bytes. The first figure we need is the sector the filesystem starts on.
    # parted /dev/sda unit s print
    Model: ATA ST9320328CS (scsi)
    Disk /dev/sda: 625142448s
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt
    Disk Flags: pmbr_boot
    
    Number  Start       End         Size        File system  Name                          Flags
     1      2048s       411647s     409600s     fat16        EFI System Partition          boot
     2      411648s     1435647s    1024000s    ext4
     3      1435648s    232122367s  230686720s
     4      232122368s  232384511s  262144s                  Microsoft reserved partition  msftres
     5      232384512s  420341759s  187957248s  ntfs
     6      420341760s  420343807s  2048s                                                  bios_grub
     7      420343808s  421367807s  1024000s    ext4
     8      421367808s  625141759s  203773952s
    
    The partition starts on sector 232384512, and the sector size is 512 bytes
  2. Calculate the size of the filesystem in sectors, and the end of the new partition
    • After resizing, the filesystem is marked as dirty so it will be checked on the next Windows boot. Clear this flag so that we can run further commands.
      #ntfsfix -d /dev/sda5
      Mounting volume... OK
      Processing of $MFT and $MFTMirr completed successfully.
      Checking the alternate boot sector... OK
      NTFS volume version is 3.1.
      NTFS partition /dev/sda5 was processed successfully.   
      
    • Find the cluster size and number of clusters.
      # ntfsinfo -m /dev/sda5|grep Cluster
          Cluster Size: 4096
          Volume Size in Clusters: 9765624
          Compression Block Clusters: 0
          Free Clusters: 2631945 (27.0%)
      
    • Calculate the size in sectors of the new filesystem.
      Equation 1. Filesystem size in sectors
      4096 bytes per cluster × 9765624 total clusters ÷ 512 bytes per sector = 78124992 sectors

    • Find the end of the new partition.
      Equation 2. End sector of new partition
      232384512 start + 78124992 filesystem = 310509504 end sector

      Adding onto the end sector value costs little free space and provides a margin of error. Consider padding the end of your partition for best results.
  3. Use parted to resize the ntfs filesystem on /dev/sda. Using the s after the number ensures parted uses sectors as the unit.
    # parted /dev/sda
    GNU Parted 3.1
    Using /dev/sda
    Welcome to GNU Parted! Type 'help' to view a list of commands.
    (parted)
    (parted) rm 5
    (parted) mkpart
    Partition name?  []? windowsdisk
    File system type?  [ext2]? ntfs                                           
    Start? 232384512s                                                         
    End? 310509504s      
    (parted) quit
    
  4. Check the partition table to confirm the free space is available, and exit parted.
    (parted) print free                                                       
    Model: ATA ST9320328CS (scsi)
    Disk /dev/sda: 320GB
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt
    Disk Flags: pmbr_boot
    
    Number  Start   End     Size    File system  Name                          Flags
            17.4kB  1049kB  1031kB  Free Space
     1      1049kB  211MB   210MB   fat16        EFI System Partition          boot
     2      211MB   735MB   524MB   ext4
     3      735MB   119GB   118GB
     4      119GB   119GB   134MB                Microsoft reserved partition  msftres
     5      119GB   159GB   40.0GB  ntfs
            159GB   215GB   56.2GB  Free Space
     
            (parted) quit
    

6. The GRUB Bootloader

6.1. GRUB Basics

Fedora uses the GRUB bootloader. Short for GNU GRand Unified Bootloader. GRUB is a powerful and versatile bootloader that meets most needs. For other platforms such as IBM System Z or cloud images, Fedora may use other bootloaders, but because they are not likely to multiboot, this document does not address them.
The primary configuration file for GRUB describes the menu presented to the user, including the options passed to each operating system definition it boots. It also contains options for GRUB itself, such as the default option, timeout before continuing to the default option, and the visual presentation of the menu.
On BIOS systems, this file is located on the boot partition, as /boot/grub2/grub.cfg.
On UEFI systems, this file is located on the UEFI system partition, as /boot/efi/EFI/fedora/grub.cfg.

Do not edit GRUB configurations directly!

Any changes made directly to the GRUB configuration files such as grub.cfg will be overwritten when the file is regenerated, such as after a kernel update. Instead of editing these files directly, edit the templates that are used to generate them. This process is covered in Section 6.4, “Configuring the GRUB Bootloader”
GRUB can identify and directly boot most Unix type operating systems. You only need one GRUB configuration to boot them all, but each should have a dedicated /boot partition. Operating systems such as Windows cannot be booted directly, but GRUB can identify and chainload them.

6.2. Changing GRUB entries at boot

Changing selection or adding arguments to a GRUB menu entry at boot time can be useful for testing or troubleshooting purposes. You might have a graphics issue to troubleshoot by booting temporarily into a non-graphical target, a hardware issue to work around with a kernel parameter, or a problem to resolve by selecting an alternate kernel. This section covers the procedure for adding boot arguments, see Section 9, “Boot Options” for some arguments you might use.

The Rescue option

The normal boot entries for Fedora use a trimmed down initramfs, or initial boot filesystem. This host-only initramfs had information only about the hardware on your computer, allowing the system to boot more quickly by avoid loading unneeded drivers.
One of the default menu entries for Fedora is a rescue entry. This will load the same Fedora environment as the other entries, but loads a full initramfs.
The rescue option is useful if you have problems after adding new hardware. You can use the rescue option to regenerate the initramfs for all boot entries using this command:
# dracut --regenerate-all --force
  1. Turn on or reboot your computer. When the GRUB menu ( Figure 1, “GRUB menu during countdown” ) appears, press the Esc key to stop the countdown.
    GRUB menu during countdown
    The GRUB menu is a text based interface with a list of bootable systems. The entries for Fedora include the kernels available to boot and the rescue option. The menu counts down from a defined value, 5 seconds by default, before booting the default entry.
    Figure 1. GRUB menu during countdown

  2. Use the arrow keys to highlight the desired boot entry.
    1. If you want to boot an alternate menu entry without editing, press Enter to continue.
    2. If you want to edit the entry before booting, press e to edit.
    1. The initial screen displayed for editing shows information GRUB needs to find and boot the operating system, as pictured in Figure 2, “The GRUB edit screen, Part 1”. These lines should not be changed.
      The GRUB edit screen, Part 1
      The initial edit screen shows several lines of parameters and modules that GRUB uses to boot the operating system.
      Figure 2. The GRUB edit screen, Part 1

    2. Using the arrow keys, move down to the line that contains the boot arguments. On UEFI systems, this line will begin with linuxefi, or on BIOS systems the line will begin with linux. The next argument on the line will typically be the kernel, a string beginning with /vmlinuz-. This is shown in Figure 3, “The GRUB edit screen, Part 1”.
      Press the End key to move to the end of the line.
      The GRUB edit screen, Part 1
      Scrolling down reveals the line with boot arguments.
      Figure 3. The GRUB edit screen, Part 1

      Getting more information during boot

      The default boot parameters for Fedora include rghb and quiet. These enable the boot splash screen instead of showing details about services, mountpoints, and other units as the sytem boots. If you are troubleshooting a boot issue or want to see more information when Fedora loads, removing these parameters will disable the splash screen.
  3. Type in your desired parameters and press Ctrl+x to boot. See Section 9, “Boot Options” for some parameters you might find useful.

6.3. Recreating GRUB

This section describes the process for reinstalling the GRUB bootloader and recreating the configuration. Unlike legacy GRUB, which required users to manually create entries, GRUB2 will scan the system for bootable systems and automatically create the menu configuration. There are a number of reasons to reinstall GRUB:
The boot menu does not include an available operating systems.
The bootloader has been overwritten during installation of Windows or another operating system.
You have chosen not to use anaconda to install grub.

6.3.1. Refreshing GRUB configuration

To recreate the GRUB configuration from a booted system, use the grub2-mkconfig utility. The program will scan your system and create menu entries for what it finds. You should also use grub2-mkconfig after customizing menu entries, a process described in Section 6.4, “Configuring the GRUB Bootloader” If Fedora does not boot because of an invalid GRUB configuration, you can perform this procedure to repair it after following the instructions in Section A.1, “Setting up a chroot from a live image”.
Refresh GRUB configuration on a BIOS system:
# grub2-mkconfig -o /boot/grub2/grub.cfg
Refresh GRUB configuration on UEFI systems:
#grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
In most cases, this operation will detect any operating system available on your computer and create entries for them in the GRUB menu. Actually reinstalling the GRUB bootloader isn't required, just reconfiguring.

6.3.2. Reinstalling GRUB

In some cases, you may need to reinstall the GRUB bootloader itself. It might be because another operating system has overwritten GRUB, or because of some inadvertent action. This section explains how to do that, but if you do have a GRUB menu or GRUB prompt, you probably don't need to perform the operations. This section assumes that you have tried all of the firmware boot options, and are sure you do not have a functioning GRUB bootloader on your system.
Be careful not to mix up the different instructions for UEFI and legacy systems. Installing the wrong implementation of GRUB can cause problems that are difficult to resolve.
6.3.2.1. Reinstalling GRUB on UEFI systems.
Procedure 3. Reinstalling GRUB on UEFI systems.
  1. Enter your installed system in a chroot using the instructions in Section A.1, “Setting up a chroot from a live image”. Be sure to boot the live image in UEFI mode.
  2. Reinstall the packages that provide bootloader files. This will recreate any Fedora files missing from the EFI system partition.
    # dnf reinstall grub2-efi shim
    
  3. Optionally, recreate the firmware boot entry. You only need to do this if the Fedora entry is missing, so check to see if the Fedora entry is present before continuing.
    Exit the chroot before creating the EFI boot entry.
    # exit
    
    1. Check the existing firmware boot entries.
      # efibootmgr -v
       BootCurrent: 0015 Timeout: 1 seconds BootOrder: 0015,0000 Boot0000* Windows Boot Manager HD(3,2e9a5000,32000,0d13443c-6bf1-4952-960c-c05ba2b3fd8c)File(\EFI\Microsoft\Boot\bootmgfw.efi)WINDOWS.........x...B.C.D.O.B.J.E.C.T.=.{.9.d.e.a.8.6.2.c.-.5.c.d.d.-.4.e.7.0.-.a.c.c.1.-.f.3.2.b.3.4.4.d.4.7.9.5.}...a............... Boot0015* Fedora HD(1,800,64000,211be689-9d4f-4034-bbc9-4e03372165db)File(\EFI\fedora\grubx64.efi) Boot0018* SATA : PORT 4 : HL-DT-ST BD-RE WH14NS40 BIOS(3,0,00)AMBO Boot0019* SATA : PORT 6G 0 : ST31500341AS : PART 0 : Boot Drive BIOS(2,0,00)AMBO 
      
    2. If the Fedora entry is missing, check the installation logs to get the command to put it back.
      # grep efibootmgr /var/log/anaconda/anaconda/program.log
       05:43:07,548 INFO program: Running... efibootmgr 05:43:07,566 INFO program: Running... efibootmgr -c -w -L Fedora -d /dev/sda -p 2 -l \EFI\fedora\shim.efi 
      
    3. Run the efibootmgr invocation again. If needed, adjust the arguments to fit your EFI system partition's location. In this example, -d /dev/sda places that partition on the /dev/sda, and -p 2 designates the second partition on the drive.
      # efibootmgr -c -w -L Fedora -d /dev/sda -p 2 -l \EFI\fedora\shim.efi
      
  4. Reboot your system into Fedora.
6.3.2.2. Reinstalling GRUB on BIOS systems.

6.4. Configuring the GRUB Bootloader

GRUB configuration files can be found in several places:
/etc/default/grub
Configuration for GRUB itself is defined in /etc/default/grub. The default options used when creating new entries for Fedora can also be found here. Most changes to Fedora's boot configuration will involve editing this file.
/etc/grub.d/
Files in /etc/grub.d are used as templates for creating new GRUB entries as well as custom boot entries.
/boot
The /boot directory contains Fedora's kernel and initramfs.
On BIOS systems, this directory also contains the configuration for GRUB itself.
/boot/efi/EFI
This directory is only found on UEFI systems, and is within the UEFI System Partition. Both GRUB configuration files and the GRUB executable can be found in /boot/efi/EFI.

6.4.1. Permanently adding to Fedora boot entries

The options that GRUB passes to Fedora when booting are generated from the discovered filesystems and from the value of GRUB_CMDLINE_LINUX in /etc/default/grub.
Adding a parameter to the end of GRUB_CMDLINE_LINUX and regenerating grub.cfg will apply the parameter to all current and future Fedora boot entries.
Example 1. In practice: Fixing backlight issues with kernel parameters
Some laptops have problems with the display backlight using the default configuration. The screen might be too bright, too dim, flicker, or even appear to be completely black.
The issue can often be resolved by directing the system to prefer vendor-specific drivers for the backlight using the acpi_backlight=vendor parameter.
  1. With root permissions, open the file /etc/default/grub.
    # nano /etc/default/grub
     GRUB_TIMEOUT=0 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" GRUB_CMDLINE_LINUX="vconsole.font=latarcyrheb-sun16 $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :) vconsole.keymap=us rhgb quiet" GRUB_DISABLE_RECOVERY="true" 
    
  2. Add the parameter to the end of GRUB_CMDLINE_LINUX and save the file.
     GRUB_TIMEOUT=0 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" GRUB_CMDLINE_LINUX="vconsole.font=latarcyrheb-sun16 $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :) vconsole.keymap=us rhgb quiet acpi_backlight=vendor" GRUB_DISABLE_RECOVERY="true" 
    
  3. Regenerate the GRUB configuration to apply the new changes.
    1. For BIOS systems:
      # grub2-mkconfig -o /boot/grub/grub2.cfg
      
    2. For UEFI systems:
      # grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
      

7. Multiboot on BIOS Systems

7.1. BIOS Basics

8. Multiboot on UEFI Systems

8.1. UEFI Basics

This section of the guide covers the UEFI boot process in general and how Fedora successfully handles a Secure Boot environment. For detailed information about the UEFI specification, read http://www.uefidk.com/learn and here http://www.uefi.org/

8.1.1. EFI Boot Sequence Explained

In this section we will consider two scenarios:
  1. How EFI handles a normal boot cycle - no intervention.
  2. What happens when you press the appropriate key to enter the EFI Settings prior to a successful boot of an operating system.
First, EFI attempts each entry in the order listed in its BootOrder variable. It will boot the first entry that 'works' with the data listed for that entry. A typical entry is in the format of: ACPI(a0341d0,0)PCI(1f,2)SATA(0,0,0)HD(1,800,64000,12029cda-8961-470d-82ba-aeb17dba91a5) File(\EFI\fedora\shim.efi)
The EFI Boot Manager begins the process of loading the file (end result) by initializing each preceeding device in order. Thus, in the example above, it starts by initializing ACPI(a0248d0,0) which then provides access to PCI(1d,2) which then provides access to SATA(0,0,0) etc.. EFI just goes down the line until it can load the file called for in that entry. If anything in that chain is broken or missing the boot fails. If it cannot boot the first entry in the BootOrder list, it will go to the second, and failing there, will move on to the third entry, etc.
If it gets to the end of the BootOrder list and still has not been able to transfer execution, it will begin to initialize every device connected to the system (fixed and removable) and begins to look specifically for removable devices. Remember, this is what happens automatically -- its what happens if you do not go into the "EFI Settings" and thereby stop the process at the end of initial enumeration of all connected devices. By hitting the 'magic' key, you alter the sequence of events and are, in effect, "Skip the boot process for now and just enumerate everything connected to the motherboard." Full enumeration is not conducted until after the BootOrder sequence has been exhausted during normal boots. Right now, we are looking at what happens automatically if EFI cannot find a bootable device by traversing its BootOrder entries.
As EFI Boot Manger moves on to find a bootable, removable device, it looks for an EFI partition, formatted in Fat32, Fat16 or Fat12 with an \EFI\Boot\ directory structure and that bootx64.efi is in that directory.
When that file is found and loaded, execution is passed to it. In Fedora, that means that bootx64.efi is going to check for the presence of fallback.efi; and if it finds it, will pass execution to it. Fallback.efi will then enumerate all of the boot.csv's it can find in its own partition, create and append an entry for each one to the EFI NVRAM, change the NextBoot variable and pass execution back to the EFI for processing. Having a valid entry, EFI will boot to that device and hand over execution.
At some point, either grubx64.efi or the kernel itself will issue a command to EFI to terminate its boot support processes and standby for a reboot, standby, hibernate or power down command. In effect, we are saying to EFI: "Ok. We got it from here."
Ubuntu, for example, has chosen to make that call just prior to loading the kernel, while Fedora continues to use EFI support services until after the kernel has verified the signatures on all boot files; thus continuing the 'chain of trust' a little further.
In any event, EFI will boot to the first device it can either find on its own, or to the one its told to.
When you enter the "EFI Settings" of your computer and look at the menu, all of that enumeration is complete before the menu is displayed. All you then have to do is select which device you wish to boot from and hit Enter.

8.1.2. What is Default Boot Behavior?"

Default Boot Behavior is an EFI process that is initiated when the EFI boot process cannot find a suitable boot manager or boot loader to pass execution to after traversing the BootOrder list.
It begins by enumerating all removable devices and then passing execution to the first instance of bootx64.efi it finds.
bootx64.efi uses fallback.efi to scan the entire EFI partition looking for boot.csv files in each sub-directory within the EFI partition. Everytime it finds one, fallback.efi creates and appends an entry in the EFI NVRAM. It then changes the BootNext variable to point to the first one it found. When finished, it directs execution back to EFI Boot Manager to boot using the NextBoot variable.

8.1.3. "What is Fallback and How Does it Work?"

The reason this process is referred to as "fallback" is because, as noted above, bootx64.efi checks to see if a file named fallback.efi is in the same directory as itself, and if so, will execute it as an EFI application.
It is the fallback.efi application that enumerates the various boot.csv files that it finds, creates and appends the EFI NVRAM entries, and finally, passes control back to the EFI Boot Manager to boot the first entry it created; which, as mentioned earlier, it does by changing the BootNext variable.
The Default Boot Behavior, which initiates fallback, happens in the event that any of the following conditions are met:
  1. There aren't any existing NVRAM entires for any installed operating systems
  2. That the entries that were listed in the BootOrder resulted in a 'no boot' situation from all installed, fixed devices
  3. That your removable device settings in your EFI Boot Order Priority are such that removable devices (Live media, etc) are listed above your installed Operating Systems menu entries.
Before moving on, I would like to add a few notes to help clariy the above information:
One caveat to all that has been said about "Default Boot Behavior": If you already have installed Operating Systems on your system that will boot normally, and you want to use "Default Boot Behavior" to boot your removable media, then please read on.
Your EFI implementation has to be 'compliant' and your EFI Boot Settings have to indicate that removable devices are higher in the list than your installed Operating Systems. This allows the EFI to find and boot the removable media (if inserted) prior to attempting to run down the normal BootOrder list.
IF that is the case, then "Default Boot Behavior" will occur on that removable device and it will boot.
IF the implementation of EFI on your system is not compliant it may never get to the point where it loads fallback.efi - it still might not boot.
The only way to know for sure, is to plug in a USB, boot using the 'magic' key to enter your EFI Settings, change your boot priorites in the EFI to put the inserted USB at the top of the list, save and exit. Leave in the USB and power on without pressing any keys. If it boots to the USB automatically then everything is working as it should. If it won't boot, and/or it is not showing up on the list of devices provided by the EFI Boot Manager, then check that the device has an \EFI\Boot directory with bootx64.efi and fallback.efi in it. If all of that is there, then either the USB is 'bad', the port you plugged it into is 'bad' (something in the device path is 'bad') or your EFI implementaton is non-compliant.
If you do not have any installed OS's on your system... Just plug in removable media that meets the criteria for EFI "Default Boot Behavior" and turn it on.

8.2. Booting on Windows Systems

8.2.1. Windows EFI Partition Files

Microsoft uses bootmgr.efi and bootmgrfw.efi as Boot Managers. bootmgr.efi is the 32 bit version and bootmgrfw.efi is the 64 bit version. Both of these files are located in the root directory of the Microsoft-created EFI partition (usually found at /dev/sda1). For EFI compatibility, they are both located at /EFI/Microsoft/Boot/ as well.
Other files found within the /EFI/Microsoft/Boot directory structure are the BCD (a registry formatted configuration file), sub-directories for language files, a memory test efi application, and the BCD log files. The BOOTSTAT.DAT file is used to flag whether a recovery mode is required.
If you need to restore these files to your EFI System Partition, you can find a copy in C:\Windows\System32\Boot.

8.3. Booting on Apple systems

This section needs help! If you would like to contribute content, you can contact the Fedora Docs team via the Docs mailing list.
If you would like to request content, file a bug via http://bugzilla.redhat.com/

9. Boot Options

Boot options come in several categories:
Systemd arguments
Kernel parameters
Dracut options

A. Common Operations

This section includes common operations you might have to perform when following various instructions in this guide.

A.1. Setting up a chroot from a live image

To operate on a Fedora installation that will not boot, you must use a chroot. The process initially uses a Fedora live image, but sets up an environment that uses the files, executables, and libraries from the installed system.
The Fedora Netinstall image has a system recovery option that will set up the chroot for a Fedora system automatically. Use the instructions here for a live image.
Be consistent about your booting methods. If you have Fedora installed Fedora in UEFI mode, boot the live image in the same way.
Procedure A.1. Creating chroot of a Fedora installation
  1. Boot a Fedora live image and open a root terminal window.
  2. Create a directory to work in.
    # mkdir /mnt/sysimage
    
  3. List the available partitions. We'll use this list to identify all the partitions your Fedora installation needs.
               # blkid
                /dev/sda1: LABEL="WINRE_DRV" UUID="C812A5BC12A5AFBC" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="3f4f9bb5-6551-4411-9cea-d06dd1d10aff" /dev/sda2: LABEL="SYSTEM_DRV" UUID="32A7-BBCC" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="f540b7b9-782a-48d2-89b4-4f0a720121cf" /dev/sda3: LABEL="LRS_ESP" UUID="F2C1-30B7" TYPE="vfat" PARTLABEL="Basic data partition" PARTUUID="cdbadfc7-e84b-4fe0-935c-28419b0082f7" /dev/sda4: PARTLABEL="Microsoft reserved partition" PARTUUID="bb3d61f2-652b-4793-a8e9-8b42e819f6bb" /dev/sda5: LABEL="Windows8_OS" UUID="7898C3F398C3ADC6" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="111e1bb0-dafd-439b-8af3-9d6b86bff9e9" /dev/sda6: LABEL="LENOVO" UUID="16E2DDF6E2DDD9D7" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="45dc466a-929d-4862-91ed-396afe2e4f59" /dev/sda7: LABEL="PBR_DRV" UUID="40A4E1E7A4E1E000" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="29b2cac6-ff56-4cf2-b62e-d04230a72294" /dev/sda8: UUID="5958dcb4-dfeb-4f6c-ba07-8b2ada8b1602" TYPE="ext4" PARTUUID="cacf80f0-3376-443d-bfb5-5d3fe689885e" /dev/sda9: UUID="PRueOy-TXAC-mKDV-NRLC-k4gt-C63H-D0zfYd" TYPE="LVM2_member" PARTUUID="555251b9-438f-4f16-9011-754620526ebe" /dev/mapper/fedora-swap: UUID="28d71a2c-1b34-4115-aa19-083373ec4d8a" TYPE="swap" /dev/mapper/fedora-root: UUID="125425e2-dd7b-46e9-8c64-6d2c5b192c76" TYPE="ext4" /dev/mapper/fedora-home: UUID="1cec1d42-8750-4746-bd36-145c1ebb2d89" TYPE="ext4" 
    
  4. Identify Fedora's root partition.
    # mount /dev/sda8 /mnt/sysimage
    # cat /mnt/sysimage/etc/fedora-release
     cat: /mnt/sysimage/etc/fedora-release: No such file or directory 
    # ls /mnt/sysimage
     config-3.17.7-300.fc21.x86_64 config-3.17.8-300.fc21.x86_64 config-3.19.0-0.rc5.git2.1.fc22.x86_64 efi elf-memtest86+-5.01 extlinux grub2 initramfs-0-rescue-39995d7d26a74b1784e7bd9a7bfefdf1.img initramfs-3.17.7-300.fc21.x86_64.img initramfs-3.17.8-300.fc21.x86_64.img initramfs-3.19.0-0.rc5.git2.1.fc22.x86_64.img initrd-plymouth.img lost+found memtest86+-5.01 System.map-3.17.7-300.fc21.x86_64 System.map-3.17.8-300.fc21.x86_64 System.map-3.19.0-0.rc5.git2.1.fc22.x86_64 vmlinuz-0-rescue-39995d7d26a74b1784e7bd9a7bfefdf1 vmlinuz-3.17.7-300.fc21.x86_64 vmlinuz-3.17.8-300.fc21.x86_64 vmlinuz-3.19.0-0.rc5.git2.1.fc22.x86_64 
    # umount /dev/sda8
    
    /dev/sda8 wasn't the root partition, since it did not contain the /etc/fedora-release file, but we did find other things inside. The vmlinuz and initramfs files are the kernels and initramfs, and they always live on /boot. Remember that for later.
    # mount /dev/mapper/fedora-root /mnt/sysimage
    # cat /mnt/sysimage/etc/fedora-release
    Fedora release 21 (Twenty One)
    
    That's the Fedora root partition, so we will leave it mounted there. Because the other filesystems use mount points inside the root partition, we mount it first.
  5. Next, identify and mount the /boot partition. We found it as /dev/sda8 already, but we can confirm by checking Fedora's /etc/fstab, the file that tells the system where to mount filesystems.
    #  grep boot /etc/fstab
     UUID=5958dcb4-dfeb-4f6c-ba07-8b2ada8b1602 /boot ext4 defaults 1 2 UUID=32A7-BBCC /boot/efi vfat umask=0077,shortname=winnt 0 0 
    
    /etc/fstab uses Universally Unique Identifiers to identify partitions. This makes sure that the right partitions get mounted in the right place, even if drive orders change. The UUID listed for /boot matches what blkid reports for /dev/sda8, so we know we have the right partition.
    # mount /dev/sda8 /mnt/sysimage/boot
    
  6. If this is a UEFI installation, mount the EFI system partition next. In this example, we found it in the previous step, and can match the UUID with blkid output. You can confirm by looking at the contents once mounted.
    # mount /dev/sda2 /mnt/sysimage/boot/efi
    # ls /mnt/sysimage/boot/efi
     /boot/efi/BOOTSECT.BAK /boot/efi/EFI: BOOT fedora Microsoft 
    
  7. Next mount the virtual filesystems that the system uses to communicate with processes and devices. These are always the same, so we can do it in one command.
    #for dir in /dev /proc /sys; do mount --bind $dir /mnt/sysimage/$dir ; done
    
  8. Enter the chroot to continue, and begin working on your Fedora installation.
    # chroot /mnt/sysimage
    
  9. When you are finished, use the exit command to leave the chroot.

B. Revision History

Revision History
Revision 1-0Mon Nov 2 2015Pete Travis
Review for F23 Release
Revision 0-7Mon Jan 5 2015Pete Travis
Adding an introductory FAQ
Revision 0-2Mon Jul 29 2013Chris Roberts
Adding UEFI Windows content
Revision 0-3Sat Oct 4 2014Roger Baran
Add lots of Windows content.
Revision 0-1Sun Jul 14 2013Pete Traviss
Initial creation of book by publican

Index