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Thread: Boot to previous kernel wiped out Ubuntu!?

  1. #1
    Join Date
    Oct 2012
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    874

    Boot to previous kernel wiped out Ubuntu!?

    Hi,

    I have a mistery on my hand.

    I am running Ubuntu 13.04 on my laptop but still use 12.04 for some of my work. 12.04 now lives on an external hard drive running kernle 3.9.6. When I need it I just boot from the external hard drive. Yesterday I booted into 12.04 only for a little bit to check for updates (there was none) so I thought maybe I should boot into an old kernel (for no particular reason) so I rebooted, saw the grub screen and chose previous kernel versions and tried to boot into kernel 3.2.0-38 and then it went crazy. It struggled for a long time and showed unknown file system and grub rescue.

    So I booted into 13.04 on my laptop (internal hard drive), plugged in the external hd with 12.04 and checked.

    fdisk -l didn't seem to find anything wrong
    Code:
    Disk /dev/sdb: 320.1 GB, 320072932352 bytes
    255 heads, 63 sectors/track, 38913 cylinders, total 625142446 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x0006b6bf
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sdb1   *        2048    41945407    20971680   83  Linux
    /dev/sdb2        41947134   564340735   261196801    5  Extended
    /dev/sdb5        41947136   325720063   141886464   83  Linux
    ...
    sdb is the exrternal drive and sdb1 is / partition for 12.04, sdb5 the /home

    But blkid didn't see sdb1 and sdb5. It found all partitions on sdb except sdb1 and sdb5

    So I fired up gparted and I saw that both sdb1 and sdb5 had file systems described as "unknown" and they appeared as blank boxes, it seemed that all the data were wiped. Ubuntu 12.04 gone!! See the screenshot (though I suspect it was not really gone, just somehow not detected)

    Fortunately I had cloned the whole system. So no sweat, I just reformatted sdb1 and sdb5 with gparted, ran fsarchiver and less than an hour later I was back in business. I rebooted a few times into kernel 3.9.6 and all worked fine, I checked for kernel 3.2.0 in synaptic and saw nothing unusual. then I tried to booted into kernel 3.2.0. again and the same thing happened.

    So I restored the image again, booted into 3.9.6, open synaptic and removed the kernel 3.2.0-38 with all the headers, rebooted and then installed them again. I noticed that there was a version change though, I couldn't find 3.2.0-38 in synpatic any more, so I installed 3.2.0-49 instead. I tried to boot into 3.2.0 again an this time it worked.

    I have restored 12.04 completely so the practical problem is solved, but I really want to know what had happened. Does anyone have an explanation?
    Thanks.
    Attached Images Attached Images

  2. #2
    Join Date
    Oct 2012
    Beans
    874

    Re: Boot to previous kernel wiped out Ubuntu!?

    Hi,

    Any possible explanation of what happened?

  3. #3
    Join Date
    Jun 2010
    Location
    London, England
    Beans
    6,534
    Distro
    Ubuntu Development Release

    Re: Boot to previous kernel wiped out Ubuntu!?

    Grub in the MBR will look for its grub.cfg file in /boot/grub on the partition it is being booted into by the set root= setting. Other settings identify the partition by a Universally Unique Identifier (UUID). A long line of alpha-numeric characters. Grub will also look for a linux kernel image and an initrd.img which in your case should have been vmlinuz-3.2.0-38-generic in /boot and initrd.img-3.2.0-38-generic.

    If Grub cannot find its way at these corners (and no doubt others) it cries Rescue! It is my guess that the kernel 3.2.0-38 was deleted at some point but you failed to boot into 12.04 and run

    Code:
    sudo update-grub
    Code:
    sudo grub-install /dev/sdb
    to rewrite grub.cfg. So, you were using an out of date grub menu that pointed to a kernel that did not exist. Did you try to boot into 12.04 from the grub menu in the MBR of the internal disk? If that had been updated recently you may not have seen that 3.2.0-38 kernel to boot into.

    My explanation might not be the correct one but I find it convincing

    Regards.
    It is a machine. It is more stupid than we are. It will not stop us from doing stupid things.
    Ubuntu user #33,200. Linux user #530,530


  4. #4
    Join Date
    Oct 2012
    Beans
    874

    Re: Boot to previous kernel wiped out Ubuntu!?

    Hi, thanks for the reply.

    When it happened the first time it was not a restored. It has been running since the begining of time so I don't think there should be any grub issue.

    After I restored the first time I did run sudo update-grub when I booted into kernel 3.9.6 before I tried again to boot into grub 3.2.0.

    But even if I didn't I should be able to just shut down the machine and reboot into 3.9.6, but I couldn't do that (got the same grub rescue unknown file system error) and grub not detecting the kernel doesn't explain why the partitions is not detected by blkid and appeared to be entirely wiped clean when viewed in gparted when I examined the hard drive from a healthy 13.04 install.
    Last edited by monkeybrain2012; June 21st, 2013 at 08:47 PM.

  5. #5
    Join Date
    Oct 2012
    Beans
    874

    Re: Boot to previous kernel wiped out Ubuntu!?

    No explanation for my mystery?

  6. #6
    Join Date
    Oct 2012
    Beans
    874

    Re: Boot to previous kernel wiped out Ubuntu!?

    Bumps. I know it is not a pressing issue as I have restored my OS, but still it bothers me.

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