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How to boot Fedora 16 into rescue mode

December 30, 2011

Returning home from the Christmas days, I installed all the Fedora 16 updates that were pending. This morning I noticed that the system freezes on reboot when it was supposed to start the graphical environment. Since I was running the AMD fglrx 11.12 proprietary driver for testing, I suspected it to be responsible.

Now, the question arose: How do you boot into rescue mode? There is no menu entry in the boot manager. I used my second system (laptop) to research.

There are basically two ways to boot Fedora 16 into rescue mode:

  1. The boot manager still works. When the default entry is highlighted, type ‘e‘ to enter edit mode and find the line that starts with ‘linux’. Add the keyword ‘single’ to that line and boot by pressing F10 (or Ctrl-X).
  2. The boot manager does no longer show up. You will have to use the Fedora installation medium of your choice to boot the system and use its rescue mode.

 

From → Fedora 16

2 Comments
  1. http://dailypackage.fedorabook.com/?/archives/158-System-Recovery-Week-Rescue-Mode-and-Reinstalling-Grub.html

    Just click above link it will reveal you complete data
    I did that it worked for me

  2. When a system is too damaged to permit booting from the hard disk drive, it’s necessary to boot from another medium. The Fedora installation discs support a “Rescue mode” in which the system is booted from the CD and the hard disk partitions are optionally mounted for access.

    To access this mode, boot from your Fedora install media and select “Rescue installed system” from the boot menu using the arrow keys and Enter or by pressing the R key (if you need to edit the boot options first — to disable ACPI, for example — navigate to the Rescue option with the arrow keys and press Tab).

    The kerenel will boot from CD and the system will prompt you to select a keyboard style and language from scrollable lists of options. You will then be given the opportunity to enable the network interfaces on the system, either by entering the IP information or by using DHCP.

    The system will then present a dialog stating that the rescue environment is about to find and mount the filesystems from your hard disk Fedora installation, and asks if you wish to continue. This is a critical question: if your filesystems are intact and you wish to access the data that is in them, you can select Continue, the default option. If you are concerned about the state of your filesystems and want to ensure that they will not be altered, but still want to access them, select Read-Only. If your filesystems are damaged, you have multiple Fedora installations, or you wish to perform an operation such as reducing the size of the root filesystem, choose Skip. After some additional messages, you will be presented with a root shell prompt.
    If you have elected to continue with read/write mounting of your filesystems, all of the files from your Fedora installation should be available under /mnt/sysimage — so the normal /etc/passwd file will be available at /mnt/sysimage/etc/passwd.

    Although regular Fedora commands and utilities are available in rescue mode, most of them will not work because of the altered paths. You can work around this issue by temporarily changing the root directory using the chroot command:

    chroot /mnt/sysimage

    However, you need to be aware that files within the mounted Fedora filesystems will not have been updated during the rescue mode boot process, including /etc/mtab and /var/log/messages. You can compensate for this by some degree by getting the information from other places (such as dmesg for kernel messages and /proc/mounts for mount information).

    If you have been forced to use rescue mode because your system’s Grub bootloader code has become damaged or has been overwritten by another bootloader, you can reinstall the Grub bootloader in rescue mode:

    Start the Grub shell with the grub command:

    # grub
    Probing devices to guess BIOS drives. This may take a long time.

    GNU GRUB version 0.97 (640K lower / 3072K upper memory)

    [ Minimal BASH-like line editing is supported. For the first word, TAB
    lists possible command completions. Anywhere else TAB lists the possible
    completions of a device/filename.]
    grub>

    Use the find command to locate the partition containing the boot files by searching for /grub/grub.conf (or /boot/grub/grub.conf if that fails). Grub will report the partition using its own syntax:

    grub> find /grub/grub.conf
    (hd0,0)

    Use the root command to configure the partition from which the boot files are to be loaded (use the partition ID from step 2):

    grub> root (hd0,0)
    Filesystem type is ext2fs, partition type 0x83

    The partition ID from step 2 can be converted to a drive ID by removiing the comma and partition number — for example, the partition (hd0,0) is on the drive (hd0). Use the setup command with this drive ID to install the Grub bootloader code:

    grub> setup (hd0)
    Checking if “/boot/grub/stage1” exists… no
    Checking if “/grub/stage1” exists… yes
    Checking if “/grub/stage2” exists… yes
    Checking if “/grub/e2fs_stage1_5” exists… yes
    Running “embed /grub/e2fs_stage1_5 (hd0)”… 16 sectors are embedded.
    succeeded
    Running “install /grub/stage1 (hd0) (hd0)1+16 p (hd0,0)/grub/stage2 /grub/grub.conf”… succeeded
    Done.

    Exit the Grub shell with quit:

    grub> quit
    #

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