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Thread: Beta does not recognize existing partitions

  1. #11
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    Re: Beta does not recognize existing partitions

    Oh, one more point: This isn't really an Ubuntu 10.10 beta-specific issue. I've seen reports of the exact same problem cropping up in earlier versions of Ubuntu and/or other distributions and/or in GParted. (I don't recall the exact circumstances offhand, but I've definitely seem reports of this exact same problem.) The fundamental cause is that the disk partitioning is at least a little bit ambiguous. Of course, a good case could be made that the installer should be better able to detect this sort of condition and offer the user intelligent options for how to proceed, like the ones I outlined in my first post in this thread. Looked at from this perspective, the developers might want to examine the issue in more detail. Unfortunately, I don't think that libparted, upon which the Ubuntu installer relies, really offers very good diagnostic or recovery options for this sort of problem. A script that uses a variety of text-mode tools, like fdisk, sgdisk, and perhaps parted, might be able to do some useful pre-screening and recovery, though....

  2. #12
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    Exclamation Re: Beta does not recognize existing partitions

    UPDATE: So I rebuilt the partition table using TestDisk (Thanks 23dornot23d!)which I already tried before this. (but i did it again for good measure)

    So when I rebooted into the live cd the installer saw a partition but no type or used space, so i tried to make 2 ext4 partitions, it failed.

    So I rebooted into the live cd once again, the installer found the partition and found the type and used space, so once again i tried to install , made two ext4 partition and both worked and everything installed fine

    But.... What the funk happened?

    THANK YOU ALL

  3. #13
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    Re: Beta does not recognize existing partitions

    Quote Originally Posted by Mooney10 View Post
    But.... What the funk happened?
    Please see my first post in this thread (#8).
    Last edited by srs5694; September 20th, 2010 at 03:41 PM. Reason: Fixing overzealous emoticon interpretation

  4. #14
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    Re: Beta does not recognize existing partitions

    Quote Originally Posted by Mooney10 View Post
    UPDATE: So I rebuilt the partition table using TestDisk (Thanks 23dornot23d!)which I already tried before this. (but i did it again for good measure)

    So when I rebooted into the live cd the installer saw a partition but no type or used space, so i tried to make 2 ext4 partitions, it failed.

    So I rebooted into the live cd once again, the installer found the partition and found the type and used space, so once again i tried to install , made two ext4 partition and both worked and everything installed fine

    But.... What the funk happened?

    THANK YOU ALL
    Same thing here ....
    I had a similar situation with my main drive in my laptop and I had a good idea that it would work - but how well testdisk works everytime I am not sure ..... my main problems seem to be with NTFS partitions though .......

    I did a webpage of the steps I took while recovering a disk and it got more complex than I was prepared for LINK it managed to get it 99% sorted

    Then I did the rest here .... Link

    The latest was my USB Terra Hard Drive .... problems seem to always be with NTFS partitions too ...... no idea why ..... the only programs on this new computer that I used to repartition have been the Linux installers ...... so it does leave me wondering if they are
    working 100% .......

    Overlaps and partitions extending beyond the end of the drive should not happen and yet they have ...... This was where mine happened in the testing so it maybe was to be expected in a way best there with the best help available ...... LINKhttp://ubuntuforums.org/showthread.p...37#post9582637

    Since this report I had no problems with repartitioning ..... until the other day when I used a old Distro to set up one OS ...... and then I had big problems again ..... luckily it was my backup drive ...... so deletiing and adding new partitions sorted the problem.

    I would love to know though if having all the different formats that are available now on one disk is a good idea , and as time goes on how do you avoid doing this ......

    Yet another format is coming out now ...... and I was quite happy with the old formats as
    nothing ever appeared to go wrong .....

    This to me is the foundation that everything sits on ..... and if this goes wrong then everything goes wrong ...... it needs to be 100% correct everytime .....

    Glad you got sorted though .....

    I would love to go deeper into this subject, but this is not my aim when using my computer ..... others that set these systems up are the ones we rely on to do all the hard work of making sure that they (the formatting tools) work for all the different situations ......

    (ext2 ext3 reiserfs jfs NTFS ext4 GPT ...... plus many more and so it continues ..... each new format getting better ..... but leaving all the legacy behind ........ to me the less formats we have in the future the better for all ...... we probably have to change at some point .....
    but if they are so much better ..... maybe the old formats need to be upgraded ..... when we are changing to later releases otherwise the legacy just keeps growing)

    Obviously this may be impractical for massive drives .... but say below 20Gig .... on older systems ...... it would possibly take an hour or so to make a new partition and move the data over - this of course would have to be given as a choice to the USER if they want to take the risk - depending on what Data they have.
    Last edited by 23dornot23d; September 20th, 2010 at 07:24 PM.

  5. #15
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    Re: Beta does not recognize existing partitions

    Quote Originally Posted by 23dornot23d View Post
    Same thing here ....
    I had a similar situation with my main drive in my laptop and I had a good idea that it would work - but how well testdisk works everytime I am not sure ..... my main problems seem to be with NTFS partitions though .......

    I did a webpage of the steps I took while recovering a disk and it got more complex than I was prepared for LINK it managed to get it 99% sorted
    Actually, it appears from your links (which I admit to only skimming, not reading in depth) that your problem and Mooney10's problems have fundamentally different causes. They're both partitioning troubles, but beyond that they're entirely different.

    The latest was my USB Terra Hard Drive .... problems seem to always be with NTFS partitions too ...... no idea why ..... the only programs on this new computer that I used to repartition have been the Linux installers ...... so it does leave me wondering if they are
    working 100% .......
    I've been trying to spot a commonality in the problem reports of mis-sized partitions but I've not found one. I've also never encountered it myself, aside from deliberately re-creating of the problem by hacking at the MBR with a hex editor. Thus, I'm not sure what tool is creating it. In fact, it's entirely possible that multiple tools are to blame; there could be similar bugs in different tools.

    Overlaps and partitions extending beyond the end of the drive should not happen and yet they have ......
    One common problem is an extended partition that ends a few sectors after the end of the hard disk. I haven't checked the numbers, but this could easily be caused by a rounding error when converting from cylinder values to sector values. Most disks end "mid-cylinder," since the cylinder values these days are entirely meaningless. Thus, if the software counts the last partial cylinder as a whole cylinder, it'll compute a sector value for the end of that cylinder that's beyond the end of the disk.

    I would love to know though if having all the different formats that are available now on one disk is a good idea , and as time goes on how do you avoid doing this ......

    Yet another format is coming out now ...... and I was quite happy with the old formats as
    nothing ever appeared to go wrong .....

    (ext2 ext3 reiserfs jfs NTFS ext4 GPT ...... plus many more and so it continues ..... each new format getting better ..... but leaving all the legacy behind ........ to me the less formats we have in the future the better for all ...... we probably have to change at some point .....
    It's unclear to me what you mean by "format," since your list mixes two entirely different types of data structures:


    • The Master Boot Record (MBR; which you don't mention) and the GUID Partition Table (GPT) are partitioning systems. They define where partitions begin and end on the disk, as well as some metadata (partition type code, boot flags, etc.) associated with each partition. It's impossible to mix both of them on one disk and be 100% legal; however, a technically illegal mixture known as a hybrid MBR does exist. As described on the page to which I linked, hybrid MBRs are not a "good idea," as you say, but they are sadly necessary for certain types of multi-booting.
    • Ext2fs, ext3fs, ext4fs, ReiserFS, JFS, and NTFS are all filesystems. These are much more complex data structures that enable named access to individual files. Filesystems are typically stored inside partitions. You can safely put as many different filesystems as you like on a single disk, so long as each resides in its own partition (or in different image files or other container data structures).



    So from the start, you need at least one from each category to use a computer. (Well, technically, you could get by without a partition table, but that would be very awkward, particularly if you want to multi-boot the system.)

    On the partitioning system side, MBR was created in the 1980s, at a time when hard disks were 5 MB (megabytes, not GB or TB) in size. MBR's designers didn't think anybody could possibly want more than four partitions, so that was the limit. It's been updated through the years to overcome this and several other limitations. Each time, it's gotten uglier, more ungainly, and more likely to cause compatibility problems because old and new OSes and utilities might treat it a bit differently. For these reasons, MBR has been well-hated for at least two decades. Today, though, it's coming up on a brick wall: It uses 32-bit pointers to identify sector values. Given a 512-byte sector size (the current standard in hard disks), this means that MBR cannot handle disks more than 2 TiB in size -- or at least, it can't handle partitions more than 2 TiB in size, and no partition may begin beyond the 2 TiB point on the disk, so even stretching things, it maxes out at 4 TiB. Given that RAID arrays routinely exceed this size and at least one 3 TiB disk is now available, this is a huge problem. It can be pushed back by increasing the sector size (as is done with the one 3 TiB disk I know of), but that'll only buy another 2-5 years life for MBR, at most. Note that it's not possible to just "tweak" MBR to use 64-bit pointers; there simply isn't enough unallocated space in the data structures to cram in more bits for the pointers.

    GPT is designed, in part, to overcome MBR's limitations. It uses 64-bit pointers and abandons all the ugly hacks that have worked their way into MBR over the years. In theory, it should be more reliable than MBR. Thus, the transition to GPT is inevitable, unless something else comes along. (I'm not aware of any other partitioning system that could possibly compete with GPT for dominance in the next few years.)

    As to filesystems, some of the differences are due to the different needs of OSes. FAT and NTFS lack features that Linux needs, and all Linux-native filesystems lack features that modern versions of Windows need. OS vendors also often have a "not-invented-here" mentality that can make it hard to standardize on just one filesystem, even when the OSes' needs are similar. Linux has accumulated an embarrassing wealth of filesystems for a variety of reasons, including filesystem donations (XFS and JFS) from other OSes and a progression of new features. For instance, ext3fs added a journal to ext2fs, which greatly speeds up system startup time after system crashes. Ext4fs extends file and filesystem size limits in ext2fs/ext3fs and improves performance. The next-generation filesystem for Linux, Btrfs, adds a number of features that are important for advanced users, and it looks like it may perform better than most of its predecessors, too. Early filesystems had filesystem size limits that have long since been exceeded, and even ext2fs and ext3fs have limits that will become issues before too long (and already are issues for some users). Thus, filesystems have proliferated.

    but if they are so much better ..... maybe the old formats need to be upgraded ..... when we are changing to later releases otherwise the legacy just keeps growing)

    Obviously this may be impractical for massive drives .... but say below 20Gig .... on older systems ...... it would possibly take an hour or so to make a new partition and move the data over - this of course would have to be given as a choice to the USER if they want to take the risk - depending on what Data they have.
    The absolute number of filesystems, partition table formats, drivers, etc. will almost certainly continue to increase over the years. At some point, some may be retired. A few already have been, such as Xiafs.

    For the most part, the effort involved in creating conversion utilities is too great to justify; the benefits of converting a filesystem in place are usually pretty small. There are exceptions to this rule, of course. It's possible to convert ext2fs to ext3fs and to convert ext3fs to ext4fs, for instance. My GPT fdisk utility can convert MBR to GPT. As a general rule, in-place conversions like this are at least a little bit risky, so forcing users to convert so that the developers can retire an obsolete filesystem or partitioning scheme would be unwise at best. Better to just wait until the old filesystem is no longer being used and then drop support for it.

    Furthermore, sometimes there are reasons to keep using an old system. Ext2fs is preferred to ext3fs on small disks, such as Linux /boot partitions, because the overhead of the ext3fs journal is too great on small disks. MBR is preferable to GPT if you're dual-booting or exchanging removable disks with an older OS that doesn't understand GPT.

  6. #16
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    Re: Beta does not recognize existing partitions

    Thanks for taking the time to go through all of that .... that makes it a lot clearer to me now .....

    I have only got involved with the filesystems due to problems that I encountered .... and found that it gets really complicated ..... your explanation clears a lot of things up especially between GPT and MBR .....

    I mistook it as another filesystem .... its a 64 bit partition table then for bigger drives in the future ....

    Actually, it appears from your links (which I admit to only skimming, not reading in depth) that your problem and Mooney10's problems have fundamentally different causes. They're both partitioning troubles, but beyond that they're entirely different.
    You are right .... but I did make sure that testdisk did handle GPT ..... that was why I posted the help page link .... its then for the person to check that this will do what they want ..... my advise was to analyse the structure first before doing anything .... and testdisk
    seems a good tool for doing that ...... and also for repairing the Boot Records ...... you obviously know the full story of how all this works in depth ...... therefore I am happy to learn from you ......

    ______________________________________________

    Also the new filesystem .....
    I was wondering why this too was coming ..... again I guess its the future sizes of drives and speed at accessing information on them.

    Btrfs, adds a number of features that are important for advanced users, and it looks like it may perform better than most of its predecessors, too. Early filesystems had filesystem size limits that have long since been exceeded,
    I keep reading reports on it and have no idea how it will be implimented ..... my worry was that like with Ext4 ..... the older OS's I had running could not identify the Ext4 partitions .... therefore I worried that using gparted frome these with Ext4 being present could cause problems ...... but you have cleared that up too , as it seems as long as the boundaries are in place set either by MBR or GPT then ..... it matters not what type of filesystem lies between these boundaries .......

    I was told a load of rubbish then when I was younger ..... because .....

    I used to mix them all the time and was told it was a bad thing to do ........... NTFS .... FAT ...... and Linux partitions .... all on the same drive ...... but I knew from trying and succeeding that they all worked ok together ..... thanks for the clarification.

    I tend to be a suck it and see person ..... if I have tried something out and it is good and works then I will advise it to others .....
    but I will always have tried it out on my own system first ...... never have I lost a piece of hardware through the things I have tried
    and have always recovered disks from bad formats ...... but I trust in the people that write these programs ......

    Would I gain anything from a change from MBR to GPT ..... my biggest hard drive is a Terrabyte ...... my guess is untill I get a bigger drive than 4 terra than its best to stay as I am .... especially if the installers are not picking it up properly yet.
    but I have been having problems with the terra drive ..... mainly due to it being slow to get recognised at boot up ........ seems I have to cold boot and then do a warm reboot to get it to pick up properly once the system sees it ok then alls fine ...... but if it does not pick it up properly things go to a crawl and I get fsync problems ...... it can also cause problems when I have all 3 USB drive plugged in at the same time as the order of them can end up set up differently .......
    ( I have a routine now for plugging them in and setting the order the same each time .... but that took some figuring out what was going on ...... as with all 3 plugged in a warm boot and a cold boot would give different results - for the order of the drives .... sda sdb sdc sdd )

    I always set it 250 Gig internal as sda ..... 300 Gig USB as sdb ...... 500 Gig USB as sdc and the
    (Terrabyte as sdd ..... but often this is only plugged in occassionally and used for backups ......)

    Cheers for the info .....
    Last edited by 23dornot23d; September 21st, 2010 at 07:09 AM.

  7. #17
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    Re: Beta does not recognize existing partitions

    Quote Originally Posted by 23dornot23d View Post
    I keep reading reports on it and have no idea how it will be implimented ..... my worry was that like with Ext4 ..... the older OS's I had running could not identify the Ext4 partitions .... therefore I worried that using gparted frome these with Ext4 being present could cause problems ...... but you have cleared that up too , as it seems as long as the boundaries are in place set either by MBR or GPT then ..... it matters not what type of filesystem lies between these boundaries .......
    Correct, but there is a caveat: There are always buggy programs (even including OSes) that go blundering in where they shouldn't. If a utility or OS doesn't understand Filesystem X but decides to go ahead and write to the partition on which it's stored, there will be problems. This sort of issue is quite rare today, but if you were to try out (say) every partitioning tool in existence, along with a dozen exotic filesystems, one of the partitioners is bound to have a bug that will cause problems.

    Would I gain anything from a change from MBR to GPT ..... my biggest hard drive is a Terrabyte ...... my guess is untill I get a bigger drive than 4 terra than its best to stay as I am .... especially if the installers are not picking it up properly yet.
    GPT has advantages on smaller drives, but they're fairly modest: GPT includes a backup of all its data structures, which protects it against accidental erasure; data structures are given CRC codes, which helps the OS or disk utility detect corruption; partitions have names that can help you tell what specific partitions are for; there's no distinction between primary, extended, and logical partitions, which simplifies partition layout; cylinder/head/sector (CHS) addressing is completely eliminated, except for the protective MBR partition; and boot loaders (particularly GRUB 2) don't rely on code being stored in unallocated space, which is a dangerous but common practice in MBR boot loaders. IMHO, these advantages are great enough, considered together, to recommend GPT for Linux-only installations or for data-only (non-boot) disks when all the OSes are capable of reading GPT. That said, there are problems with GPT, mostly because of utilities that are still a little rough around the edges with GPT. The worst (and thankfully rare) of these problems are some buggy BIOSes that give booting headaches.

    Of course, all this is aside from the big issue, which is the 2 TiB limit of MBR. Note that although it's possible to create an MBR partition layout that reaches just shy of 4 TiB, that's stretching things and imposes unusual restraints on partition sizes and locations; 2 TiB is the practical limit, at least with 512-byte sectors.

    but I have been having problems with the terra drive ..... mainly due to it being slow to get recognised at boot up ........ seems I have to cold boot and then do a warm reboot to get it to pick up properly once the system sees it ok then alls fine ......
    It sounds like your drive is slow to get warmed up. You might check your BIOS settings to see if there's an option to delay the boot process a bit longer for drive startup. If not, it's conceivable that disabling the "fast boot" option in the BIOS would help. That option normally disables a lengthy RAM check. If the BIOS activates the hard disk before the RAM check, then this would give it time to spin up. I'm not positive this would work, though.

    If the problem is in the Linux drivers, perhaps there's a driver option that would cause the driver to wait longer for new drives to spin up. I haven't looked into this, though.

    but if it does not pick it up properly things go to a crawl and I get fsync problems ...... it can also cause problems when I have all 3 USB drive plugged in at the same time as the order of them can end up set up differently .......
    This shouldn't be a problem if you use UUIDs or labels to identify drives in /etc/fstab, as in:

    Code:
    UUID=3631a288-673e-40f5-9e96-6539fec468e9  /home  reiserfs  defaults  0 0
    If that filesystem is on /dev/sdb one time and /dev/sdc another, it won't matter. It's also possible to use UUIDs in GRUB, if the naming issues cause boot problems.

  8. #18
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    Re: Beta does not recognize existing partitions

    A quick update and thanks again for the in depth reply .....

    __________________________________________________ _____________

    Just to clarify the last statement and situation .... the uuids are not a problem its something to do with it recognozing one
    USB Drive ...
    ( You do not need to reply to this but I thought I would clarify what the situation is
    as it boots ok with the other two smaller USB drives ...... and it may just be a drive compatibility problem or the BIOS or the slow boot time )

    From a cold boot even with the memory test enabled and also as the CD as first drive to slow the boot even more ...
    I try to give it as much time as possible now to pick up the SLOW USB drive .... and it still has a problem.

    On the very first boot with the Terra USB drive plugged in - it will leave a flashing cursor top left on a black screen and sits there flashing forever .....

    It could be a BIOS issue ..... but is there a way of testing for it ?
    ( I doubt it very much - and even if there is its not that big a problem as the other USB drives are fine )
    It does not seem to recognise the drive other than giving it power and spinning it up ......

    BUT ......

    If I plug the Terra USB drive in at the point the internal drive menu pops up ......
    sda (internal drive) BOOT MENU pops up
    from a complete cold start ........ it seems then to be able to recognise the drive properly .... this is an IOMEGA TERRA DRIVE
    ( I do not know of any issues with it ....... but maybe others have similar problems.
    if so feel free to comment here if you happen to read this )

    Then I press CTRL + ALT + DEL ..... doing a warm re-boot it will then correctly boot to the Terra Drive ....
    sdb (external Terra USB) BOOT MENU

    Then the computer runs fine for the continuing session allowing as many warm boots as I want and runs perfectly well.


    But ..... if I switch it off and come back to it ..... then I have to do this same procedure above again to get it to work properly.

    Its a small inconvenience .... but not a major problem .... and

    I have a work around now so its not really too much of an issue ..... but it would be interesting to know for sure what is happening ..... but we have now digressed from the original problem and I am sure that your time is valuable ..... so this is just for information really ...... it may be useful to someone at sometime ..... but probably not the OP ......

    But I am glad that he got his problem sorted and I hope that it is still running ok .....
    Ok all for now and thank you very much for all the useful information.
    Last edited by 23dornot23d; September 22nd, 2010 at 05:06 AM.

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