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Thread: Hard drives changed sdx designations... should I be worried?

  1. #1
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    Hard drives changed sdx designations... should I be worried?

    Previously my hard drive setup was like this:

    /dev/sda - Windows partition, has sda1 and sda2
    /dev/sdb - Ubuntu partition, has sdb1, sdb2, sdb5, sdb6, sdb7; no idea why they skipped sdb3 and sdb4

    /dev/sdc - External drive. Backups and files and stuff. Has sdc1 only.

    But now, I found that the computer didn't recognize the External drive.

    sudo fdisk -l revealed that:

    /dev/sda (Windows) was now /dev/sdf (with sdf1 and sdf2)
    /dev/sdb (Ubuntu) was now /dev/sdg (with sdg1, sdg2, sdg5, sdg6, sdg7)

    The partition numbers are the same; the new partition numbers for the Ubuntu drive still skipped 3 and 4.

    ... and once I got the external drive recognized again, my external drive /dev/sdc was now /dev/sda, with the partition being /dev/sda1.

    Is this a cause for alarm? Might my computer write over data in /dev/sda1? I will disconnect my external hard drive before I shut down this computer just in case but... it's kind of weird.
    Last edited by akiratheoni; December 31st, 2012 at 03:44 AM.

  2. #2
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    Re: Hard drives changed sdx designations... should I be worried?

    Unless you have a non-standard setup, sda/sdb etc are no longer used, at least not when the system is running.

    If you run cat /etc/fstab, you will see that partitions are mounted by UUID and not by device; UUIDs are unique for each partition.
    Code:
    wim@aa0:~$ cat /etc/fstab
    # /etc/fstab: static file system information.
    #
    # Use 'blkid' to print the universally unique identifier for a
    # device; this may be used with UUID= as a more robust way to name devices
    # that works even if disks are added and removed. See fstab(5).
    #
    # <file system> <mount point>   <type>  <options>       <dump>  <pass>
    proc            /proc           proc    defaults        0       0
    # / was on /dev/sda1 during installation
    UUID=4e8c9e38-845f-435a-b24a-ef8c37cba4a2 /               ext4    noatime,errors=remount-ro 0       1
    # swap was on /dev/sda5 during installation
    UUID=ef260aa3-f22f-4730-8517-8546c15cba30 none            swap    sw              0       0
    #/dev/sdb1       /media/cdrom0   udf,iso9660 user,noauto     0       0
    wim@aa0:~$
    The same applies when you insert a memory stick or pendrive. If they have a label, that will be used, else the UUID will be used. You can see it when it's connected by running ls /media in a terminal; you will see e.g. /media/pendrive (label of the memory stick is 'pendrive') or /media/longnumber (UUID).
    So under Linux, I would not be worried. If you manually (or using your own scripts) mount by device, the story will be different!

    I'm not sure what Windows does but if you can still see everything as expected, there is no reason for concern.
    If you don't make backups of your important data, your data is obviously not important to you.

  3. #3
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    Re: Hard drives changed sdx designations... should I be worried?

    I have a mix of pata, sata drives in one of my rigs and get this changing behavior.
    I also see this if I have a card reader or USB hub attached.
    Yes it's disconcerting at times, I try to not boot with them attached and to mount later to avoid drives getting skewed.

    I had big problems with grub before uuid's was implemented for booting, but I always check what my system is seeing as drive designations before I do any command line operations re: writing to drives and partitions.
    Pay attention and you should be okay.
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  4. #4
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    Re: Hard drives changed sdx designations... should I be worried?

    Quote Originally Posted by Wim Sturkenboom View Post
    Unless you have a non-standard setup, sda/sdb etc are no longer used, at least not when the system is running.

    If you run cat /etc/fstab, you will see that partitions are mounted by UUID and not by device; UUIDs are unique for each partition.
    Code:
    wim@aa0:~$ cat /etc/fstab
    # /etc/fstab: static file system information.
    #
    # Use 'blkid' to print the universally unique identifier for a
    # device; this may be used with UUID= as a more robust way to name devices
    # that works even if disks are added and removed. See fstab(5).
    #
    # <file system> <mount point>   <type>  <options>       <dump>  <pass>
    proc            /proc           proc    defaults        0       0
    # / was on /dev/sda1 during installation
    UUID=4e8c9e38-845f-435a-b24a-ef8c37cba4a2 /               ext4    noatime,errors=remount-ro 0       1
    # swap was on /dev/sda5 during installation
    UUID=ef260aa3-f22f-4730-8517-8546c15cba30 none            swap    sw              0       0
    #/dev/sdb1       /media/cdrom0   udf,iso9660 user,noauto     0       0
    wim@aa0:~$
    The same applies when you insert a memory stick or pendrive. If they have a label, that will be used, else the UUID will be used. You can see it when it's connected by running ls /media in a terminal; you will see e.g. /media/pendrive (label of the memory stick is 'pendrive') or /media/longnumber (UUID).
    So under Linux, I would not be worried. If you manually (or using your own scripts) mount by device, the story will be different!

    I'm not sure what Windows does but if you can still see everything as expected, there is no reason for concern.
    Thanks so much for the answer. I haven't used Ubuntu lately, so it's my first time using Ubuntu in a long time, and I wasn't aware of the UUID change. It looks like that my /etc/fstab all mount though UUID and not the /dev/sdx way, so I think I'll be OK. Thanks!

  5. #5
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    Re: Hard drives changed sdx designations... should I be worried?

    /dev/sdb - Ubuntu partition, has sdb1, sdb2, sdb5, sdb6, sdb7; no idea why they skipped sdb3 and sdb4
    From the looks it seems you have one primary partition and one extended partition(sdb1 and sdb2).
    Typically, 1,2,3,4 are designated for primary partitions(extended are primary) and 5 and up for logical partitions.
    It's normal to set it up like this and see the 3rd, and 4th not listed.
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  6. #6
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    Re: Hard drives changed sdx designations... should I be worried?

    Quote Originally Posted by deadflowr View Post
    From the looks it seems you have one primary partition and one extended partition(sdb1 and sdb2).
    Typically, 1,2,3,4 are designated for primary partitions(extended are primary) and 5 and up for logical partitions.
    It's normal to set it up like this and see the 3rd, and 4th not listed.
    OK now that you mention the primary and logical partitions, I'm pretty sure that's what it did. As I said earlier I haven't used Ubuntu in awhile (I installed this Ubuntu 12.04 back in May and haven't really used it since) so I forgot about the primary/logical thing. So that explains it! Thanks.

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