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Thread: 10.4 won't boot in presence of Gentoo drive

  1. #1
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    Nov 2010
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    Up north
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    Ubuntu 10.04 Lucid Lynx

    Question 10.4 won't boot in presence of Gentoo drive

    I've taken the plunge and embarked on my very first install/congifuration of Ubuntu. I've successfully installed 10.04 from the LiveCD onto a brand-new 500 GB hard drive. It boots fine. At least, it did until I reconnected another hard drive that contains a Gentoo system. (I had unplugged the Gentoo drive during the installation so as not risk mucking it up).

    In the presence of the Gentoo drive, the Ubuntu system starts to boot, but then fails with an a error that it's unable to mount /var.
    Investigation (df -k) indicates that it's mounted one of the parititions on the Gentoo drive. If I unplug the Gentoo hard drive, the Ubuntu system agains boots properly.

    Being a Ubuntu neophyte, I have no idea why the 10.04 system even sees the other drive, much less mounts one of its partitions. My intent, once migrating to Ubuntu, was to copy needed user files and data from the old Gentoo system, then repartition the drive and use it for additional Ubuntu storage. Seems I can't get there from here.

    Is there some feature in Ubuntu that causes it to go looking for any other drives accessible on a system and then go about mounting random partitions?

  2. #2
    Join Date
    Apr 2009
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    Rawalpindi, Pakistan
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    5,666
    Distro
    Ubuntu Gnome Development Release

    Re: 10.4 won't boot in presence of Gentoo drive

    Is there some feature in Ubuntu that causes it to go looking for any other drives accessible on a system and then go about mounting random partitions?
    Not at all. Addition of 2nd HDD should not trouble Ubuntu. Its something weird.

    Did you look under /etc/fstab if any mount points for your 2nd hdd are defined there? By mistake...

    It would be better if you could post the output of,

    Code:
    cat /etc/fstab

  3. #3
    Join Date
    Nov 2010
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    Up north
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    Ubuntu 10.04 Lucid Lynx

    Re: 10.4 won't boot in presence of Gentoo drive

    @sikander,
    The error that appears at boot (overlaying the Mythbuntu splash screen, since I installed from the Mythbuntu LiveCD) says:
    " The disk drive for /var is not ready or not present".

    Here's what I get from cat /etc/fstab:
    Code:
    proc /proc  proc nodev,noexec,nosuid  0   0
    UUID=205b8a...  /          ext4 errors=remoun -ro  0  1
    /dev/sda1   /boot  ext2  defaults   0  2
    UUID=36dbae...  /home  ext4  defaults  0  2
    /dev/sda5   /var   ext4   defaults   0  2  
    UUID=b7fc8...  none   swap  sw  0  0
    Note that I had to copy this by hand from the display and then type it into this posting. The UUID strings are actually much longer; I've shortened them with the "..."

    The results of df -k are perhaps more revealing
    Code:
    /dev/sdc2   nn  nn  nn  7%  /
    none          nn  nn  nn  1% /dev
    none          nn  nn  nn  1% /dev
    none          nn  nn  nn  1% /dev
    none          nn  nn  nn  1% /dev
    none          nn  nn  nn  1% /dev
    /dev/sda1   nn  nn  nn  8% /boot
    /dev/sdc6   nn  nn  nn  2% /home
    Again, I've had to enter this all by hand. I've replaced the various block counts with "nn", as I didn't think the exact numbers were relevant.

    Note the /dev/sda1 mount point for /boot. It's a different drive than / and /home.
    The hard drive at /sda is my old Gentoo drive. The hard drive at sdc is my new Ubuntu drive.

    This seems really weird, and I am a real neophyte on this stuff, but it appears that Ubuntu has mounted the Gentoo drive for /boot.

    I have a theory on what's going on. The Ubuntu drive is presently plugged into a different controller than when I formatted it. I have two SATA controllers: one is on-board and one is an add-in PCI card. The former only supports 1.5 Gbps transfers, and I had a lot of problems getting my new drive (purchased for the Ubuntu install) to work. I didn't know about different SATA speeds, nor that some drives (not all) can be jumpered for backwards compatibility. So I was moving drives back and forth troubleshooting. I finally deduced that some drives HAD to be on the faster PCI controller.

    In any event, I surmise that the fstab has definitions relating to actual physical interfaces (the sda definitions in fstab) that are no longer correct. I don't understand why some of the fstab entires are sd** format and others are UUID. They were all done by the Ubuntu LiveCD. I made no manual edits to fstab (frankly, the entire fstab drives and partitions stuff is all black magic to me).

    On the assumption that my fstab config is bad, how can I fix it without starting all over from scratch? Note that if I unplug the Gentoo drive, the Ubuntu system boots up just fine.

    Thanks for the help.
    Dave

  4. #4
    Join Date
    Nov 2010
    Location
    Up north
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    79
    Distro
    Ubuntu 10.04 Lucid Lynx

    Re: 10.4 won't boot in presence of Gentoo drive

    @sikander,

    Problem solved!
    I edited fstab and changed the two references from /dev/sda* to the UUID references, pointing at the approriate partitions on my Ubuntu disk regardless of where it's plugged in or what other drives are connected.

    I discovered the proper UUID references to use with:
    Code:
    sudo blkid -o value -s UUID /dev/sda1
    sudo blkid -o value -s UUID /dev/sda5
    Through this exercise, I learned that:
    - when Ubuntu installer creates fstab, it uses a mix of device definitions and UUID definitions. That inconsistency probably has a good reason, but it can wreak havok if/when the underlying h/w environment changes.
    - if I have drives connected (and powered) to the internal SATA interface on my mobo, they are assigned sda and sdb. Drives on my PCI SATA interface are designated sdc and sdd. However, it there are no drives on the internal SATA, the PCI drives become sda and sdb, even though the internal controller is still present.

    Thanks so much for your suggestion. I now know that addition of new drives can throw Ubuntu into a tizzy.

    Dave

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