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Thread: Installing Kubuntu 7.10 on Software RAID5

  1. #21
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    Re: Installing Kubuntu 7.10 on Software RAID5

    I try to change the boot sequence, and it does not work, i also try disconecting a diferent hard drive at tha same time (always two connected) and the same thing happen. Any other ideas??

    rgotten

  2. #22
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    Re: Installing Kubuntu 7.10 on Software RAID5

    Rgotten,

    I'm afraid I'm out of great ideas. I tested my system to see that I could boot for other drives by changing the drive in the boot menu. I don't think I tried all five of my drives, but I did boot from at least three with no problems at all. But that was done with all five running. I never tried to disconnect one and then boot. I also did RAID testing by "failing" drives with the mdadm command. Everything worked fine doing that.

    It appears from the error output you posted that it is actually finding and loading the kernel but then doesn't correctly mount the root filesystem. That's why it can't find /etc/fstab and it can't mount the in-memory filesystems like /proc (the root filesystem isn't there).

    When you get the busybox prompt, run dmesg and look at the output to see where the initial error is. I suspect that there is an error that has scrolled off the screen and you're just seeing the end result.

    When you boot, bring up the boot menu and check what the "root" filesystem is. There should be a line similar to "kernel /vmlinuz-2.6.22-14-generic root=/dev/md2 ro quiet splash". What is "root=???"? Is it the root RAID partition, or something else?

    These are some things to check. I'll see if I come up with more. Basically, we need to determine where it is failing first.

    --Lloyd

  3. #23
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    Re: Installing Kubuntu 7.10 on Software RAID5

    root file system is /dev/md2. root is (hd0,0). Also when i was trying to change (hd0,0) to (hd1,0), i click on "e" and was able to change it but how do i save it, when i go out, it stays as (hd0,0).
    In the past when i was researching before i came to your thread, i look at this http://users.piuha.net/martti/comp/ubuntu/en/raid.html, there is a warning at the end with some bugs reported for version 7.10 like this one: https://bugs.launchpad.net/ubuntu/+bug/120375 and this one: https://bugs.launchpad.net/ubuntu/+bug/157648, what do you think about this, and do you think this could be the problem?

    Also how do i run dmesg on the busybox??

    Evidently, i removed a hard drive, since in my opinion if one of them fails wound't this be a similar situation for a hard drive failure and that is when you want the system to work until you replace the hard drive?

    Also, what do you think about version 8.04 should i try that, do you think that this can make a difference??

  4. #24
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    Re: Installing Kubuntu 7.10 on Software RAID5

    Rgotten,

    This (https://bugs.launchpad.net/ubuntu/+bug/120375) looks like it is exactly the problem you are having. At the end of this very long thread are some workarounds that show a lot of promise. But I'd guess you'll need to read the entire thread to understand all of it. Now you have me thinking that I have a vulnerability to address! Yes, a disconnected drive definitely simulates one potential error situation. And I should probably try that myself and work through this issue.

    I could be wrong, but I thought dmesg was included in the busybox command set. If so, you can just enter dmesg and hit ENTER. Of course, there will be lots of stuff that scrolls by. You might need to redirect output to a file and then look at the file in an editor.

    I have no opinion on using 8.04, except if I were installing today that's what I'd use. You should look at the change logs and see if the bug has been addressed. If you want to restart from scratch with 8.04, you could give it a try. I did find that after I'd run the installation a few times, I could do the whole thing fairly quickly, other than waiting for it to sync large RAID arrays.

    I am going to take a look at this issue with my own system and implement the work around if I need to. But I don't know when I'll get to it.

    --Lloyd

  5. #25
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    Re: Installing Kubuntu 7.10 on Software RAID5

    Let me ask you another question, i learned how to check the partitions and found the following with the fdsik -l command: each one of the disk says: Dsik /dev/md6 doesn't coantain a valid partition table...the same thing with 1 or 2 or 3 or 4 or 5..Why

    Thanks one more time for your help

  6. #26
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    Re: Installing Kubuntu 7.10 on Software RAID5

    Rgotten,

    When you "partition" a drive, you slice up the drive into different segments/partitions. For example, when you partition /dev/hda, you end up with /dev/hda1, /dev/hda2, /dev/hda3, and so on. The partition table is stored on /dev/hda, the base "drive", not on each partition. When you run "fdisk -l /dev/hda2", for example, it actually reads the partition table from /dev/hda. Make sense? At least that is my understanding.

    So, where is /dev/md? Well, there isn't one. So when you run "fdisk -l /dev/md2", it can't find /dev/md and thus can't find the partition table. The raid devices are "software devices" and the actual configuration is in mdadm.conf, not on the drives themselves. The drives themselves have the "hard" partitions, like hda1, hda2, etc.

    Generally, the primary reason for the partition table is so various tools can read it and use it to manage partition sizes. Since the actual size of the RAID array is based on the size of the constituent partitions on the drives, it really can't be "managed", i.e. grown, shrunken, etc. To do that, you have to actually manage the size of the constituent partitions. Thus, having a partition table for the RAID device isn't particularly useful.

    I don't know of any issue with not having a partition table for the RAID devices.

    --Lloyd

  7. #27
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    Re: Installing Kubuntu 7.10 on Software RAID5

    how do i check then were / /var /usr and home are located..let say i want to go to my root or my home folder

    rgotten

  8. #28
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    Re: Installing Kubuntu 7.10 on Software RAID5

    I'm not sure I understand your question. But I think this is pretty simple, basic Linux/Unix stuff. The root filesystem is mounted as "/". So if you want to go to the root, cd to /. The root filesystem has empty directories for usr, tmp, var and home (and potentially others). These are the mount points for those filesystems. The usr filesystem is mounted on /usr, the var filesystem on /var, etc. If you want to go to the usr filesystem, you simple cd to somewhere in /usr. Once a filesystem is mounted, the mount point will no longer appear to be empty. For example, if you look at /usr before it is mounted it will be empty. After it's mounted, it will appear full of lots of things, like /usr/bin, /usr/local, etc. All this is a little difficult to see because all these filesystems need to be mounted for a working system. But if you put a CD in your CD drive it should mount on /media/cdrom0 (I believe). If you look at /media/cdrom0 before putting the CD in, it will be empty. After you put the CD in, it will show all the files on the CD.

    You can see all the mounted devices by simply enter the "mount" command (no parameters) at a command prompt. If you're not the superuser, you'll only see the ones accessible to you. To see everything, do "sudo mount". An entry will look something like "/dev/md6 on /home type ext3 (rw)", which tells you /dev/md6 is mounted on the mount point /home, it has an ext3 filesystem and it's mounted read-write (rw). Using the mount command is the quick way to see all that's mounted.

    Being new to all this, you might want to pick up a basic Linux book. There are some specific to Ubuntu. Play around a bit with basic commands to learn. The GUI is always nice, but to do many admin tasks on any Linux distro you have to get comfortable with the shell and a text editor. You will frequently need to use those for admin work.

    --Lloyd

  9. #29
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    Feb 2008
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    Re: Installing Kubuntu 7.10 on Software RAID5

    When install version 8.04, and i disconect either of the hard drive it appears to boot and i get a message that says: start the raid in degrade (or somethng similar), with the command mdadm -R /dev/mdx ( in version 7.10, i have to install the boot insruction in each one of the hard drive). Since i am getting this message, does this mean that the newer version has the bug fixed in regards to the instruction on how to boot in each one of the hard drive??

    How can i check each hard drive to be sure they have this instruction and that i have installed grub also on the second disk's (/dev/sdb) master boot record (MBR), as well as the third. ??

    thanks one more time

    rgotten
    Last edited by rgotten; April 29th, 2008 at 03:41 PM.

  10. #30
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    Re: Installing Kubuntu 7.10 on Software RAID5

    Rgotten,

    I don't think I can help you with this latest question. There were some hints in this: https://bugs.launchpad.net/ubuntu/+bug/120375. But I didn't read it well enough to be able to tell you where to look for changes. You may want to post your question in the Installation & Upgrades forum. There should be some experts in the community watching that forum and perhaps they can answer your question. You should refer to the URL above and ask specifically about that bug.

    Sorry I can't be of more help on this one. I'd have to reinstall and play with it to be able to answer your question.

    --Lloyd

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