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    Imaging Linux systems, UUID for swap not matching on deployed systems. Eh?

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    • I
      ianabc Testers
      last edited by

      Hi Jason, I use device names rather than UUIDs in all of my linux images but I’ve never actually had to use the instructions at the end - I gave it as a worst case scenario.

      For ext4 filesystems, they stash the UUID in the superblock so I think that i why they still work - you could probably continue to use UUIDs for ext filesystems, I just choose not to.

      The other thing is, swap is just swap. You can blow it away and recreate it with pretty much no system impact.

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      • J
        Jason Sauders
        last edited by

        The only question about that would be… is swap still usable by the system if the UUID of the swap partition did not match to ‘mount’ it? I look at it like this… if swap is just swap (which I believe), then why even bother fstab’ing it? Since the system automatically adds swap to fstab I can’t help but to think there’s a reason for that.

        Thanks for your response!

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        • I
          ianabc Testers
          last edited by

          Hi Jason, bear with me, I’m not really sure I understand the question. The system doesn’t add swap automatically, installers sometimes do, but it is a reversible or modifiable choice at your discretion. The swapon and swapoff commands will let you turn any of your swap files/partitions on and off.

          If the UUID of the swap partition doesn’t match the fstab it won’t be used. To get around that, you would either need to modify the fstab or modify the swap partition (swaplabel will let you change the UUID).

          What I was suggesting at the top of the thread was that if your client systems don’t vary too much, then the device names will not change (i.e. /dev/sda will always be /dev/sda) and you can put the device names in fstab instead of UUIDs - this avoids the need for editing the fstab or the swap uuid in the future.

          Does that help?

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          • J
            Jason Sauders
            last edited by

            Hey there. Yes - it does. More than anything I just wanted confirmation that the UUID did need to match in fstab in order for swap to be used, as I simply couldn’t wrap my brain around how swap WOULD work with mismatched UUIDs. So that clarifies things a bit.

            I could use the device ID, but I guess I’m just a believer in sticking to UUIDs due to their accuracy. The systems can vary wildly, I’m talking from a desktop made in the very early XP era to a two year old laptop, all running from the same image.

            I still can’t really understand how the UUID is changing, though. What I do is I built the image on a 40 GB HDD, the smallest HDD I deal with. I blast that to the drives and expand the EXT4 partition to utilize the entirety of the space on the disk. To give you a little feedback as to what I’m doing, this is the basic jist. I work for a large public school district in the IT department. While the vast majority of our systems are Ubuntu, we do indeed use FOG for imaging the handful of Windows systems that are in-house. I’ve used FOG at my last district I worked at (all Windows based) with flying success. It felt like a natural course of action since FOG is, well, pretty much awesome. Our district is quite large, and spans a huge geographical area. A decent portion of the district is of lesser income individuals. As a result, I accept older computers from the XP generation and newer from pretty much anybody who wants to get rid of them. After using DBAN on the drives, or FOG’s full disk wipe, I put Xubuntu fully loaded with a lot of software, including educational software, on the computers for these people. All in all, I basically repurpose old computers and donate them to families who can utilize them, all free of cost, all running free and open source software. The point is to ensure that no families are left out unable to have a computer for their kids to do homework on; something that’s growing increasingly common (do I dare say, important) given the level of dependency with technology that districts are growing towards. Point of this story is to highlight exactly why (and how much) the systems I deal with can vary in hardware.

            Given that Clonezilla does not change the UUID, it makes me wonder what process under the hood is operating differently versus FOG. I ‘thought’ FOG and Clonezilla were both built on a lot of the same core fundamental technologies. Since I am not imaging thousands of these systems at the same time, Clonezilla Live might be more suitable for a predictable image deployment, as I can simply house the image on my server and pull it over my gigabit LAN via SSH or SMB. I’d like to get FOG to work though in the event that we want to utilize it for our Linux systems, despite the fact we’re running our own imaging platform that was largely built by some of our HS tech interns (hosted on github, known as FLDT). But hey, options are nice, so it’d be nice to use FOG at home and know how to work around this in the event we ever want to put FOG to use at work.

            I do have to wonder if FOG is being a bit fussy with the UUIDs in regard to how I’m imaging the drives. I have a spare tower on my desk with multiple IDE and SATA ports, so I drop the drives in that tower and PXE boot that tower to handle the images via FOG, or USB boot via Clonezilla Live. So the system that is running with the drives is not the system that the drive sees when it’s 100% packaged up and ready to go. Perhaps this is where FOG is getting miffed? Hard to say, but given an image is an image is an image, it would confuse me if this was the culprit.

            At any rate, just some rambling thoughts and whatnot. Thanks again for your assistance - it’s appreciated!

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            • I
              ianabc Testers
              last edited by

              Hi Jason, the fog script fog.download does an “mkswap” on the partition during the restore. I think that will change the UUID. The alternative would be to just dd the entire swap space which is probably what Clonezilla is doing (though I’m guessing :)).

              Reading what you are doing (congratulations by the way - a very laudable project!) there are a couple of ways you could solve this. They all come in at the time you are expanding the ext4 filesystem. At the same time you would update either the fstab or the UUID in the swap partition. After the next reboot (or after a swapon/swapoff) your swap partition would show up.

              To edit the fstab I might do something like
              [CODE]
              #!/bin/sh

              OLDUID=grep swap /etc/fstab |cut -d' ' -f1
              NEWUID=blkid | grep swap | cut -d' ' -f2

              sed “s/$OLDUID/$NEWUID/” /etc/fstab
              [/CODE]
              before I expand the ext4fs.

              If you wanted to modify the swap UUID instead, then something like
              [CODE]
              #!/bin/sh

              TARGETUID=grep swap /etc/fstab |cut -d' ' -f1 | cut -d'=' -f2
              DEVICE=blkid | grep swap | cut -d':' -f1

              swaplabel -U “$TARGETUID” $DEVICE
              swapon -a
              [/CODE]

              A third alternative is to use labels rather than UUIDs or device names.

              K 1 Reply Last reply Reply Quote 0
              • H
                Hongyun
                last edited by

                I’m having the same problem with Mageia 4 system. Attached image is what’s show up after deployed a computer. It only complaints about the swap partition UUID.

                And before I upload the image, I’ve already changed the fstab file to use either the disk name /dev/sda5, or the label of the swap partition LABEL=SWAP, in both cases, I get the same result.

                Any idea how to fix this?

                Thanks,
                Hongyun

                [url=“/_imported_xf_attachments/1/1210_dracut_error.JPG?:”]dracut_error.JPG[/url]

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                • Tom ElliottT
                  Tom Elliott
                  last edited by

                  [quote=“Hongyun, post: 34056, member: 1117”]I’m having the same problem with Mageia 4 system. Attached image is what’s show up after deployed a computer. It only complaints about the swap partition UUID.

                  And before I upload the image, I’ve already changed the fstab file to use either the disk name /dev/sda5, or the label of the swap partition LABEL=SWAP, in both cases, I get the same result.

                  Any idea how to fix this?

                  Thanks,
                  Hongyun[/quote]

                  What version of FOG are you running?

                  Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG! Get in contact with me (chat bubble in the top right corner) if you want to join in.

                  Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

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                  • H
                    Hongyun
                    last edited by

                    The newest version 1.1.2

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                    • Tom ElliottT
                      Tom Elliott
                      last edited by

                      Chances are that’s the majority of the problem. I don’t think it did the correct things for the UUID.

                      Can you upgrade to 1.2.0 and reupload the original image and test again?

                      Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG! Get in contact with me (chat bubble in the top right corner) if you want to join in.

                      Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                      Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

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                      • H
                        Hongyun
                        last edited by

                        I just upgrade the FOG server, you have a 1.2.0 now? That was fast, I will try the new version. Thanks!

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                        • H
                          Hongyun
                          last edited by

                          I found each time after I upgrade FOG, the /etc/exports file got overwritten, I have to re-enter all my storage nodes again to make it work. Is it possible you can keep that file in your next version? Just some thoughts 🙂

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                          • H
                            Hongyun
                            last edited by

                            Hi Tom,
                            I tried the new version, result is the same 😞 any other suggestions?

                            Thanks,
                            Hongyun

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                            • Tom ElliottT
                              Tom Elliott
                              last edited by

                              Did you reupload the image or just try redeploying?

                              Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG! Get in contact with me (chat bubble in the top right corner) if you want to join in.

                              Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                              Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

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                              • H
                                Hongyun
                                last edited by

                                Yes, I reuploaded the image after the upgrade yesterday, and redeployed the computer today.

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                                • H
                                  Hongyun
                                  last edited by

                                  I think it has something to do with the OS. I tried reupload a working image and then download it again, it still works. But this Mageia 4.1 OS doesn’t work properly. I will try to reinstall it with ext3 partition to see if it works.

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                                  • I
                                    ianabc Testers
                                    last edited by

                                    [quote=“Hongyun, post: 34129, member: 1117”]I think it has something to do with the OS. I tried reupload a working image and then download it again, it still works. But this Mageia 4.1 OS doesn’t work properly. I will try to reinstall it with ext3 partition to see if it works.[/quote]

                                    UUIDs work for ext3 and ext4 filesystems because the UUID is part of the filesystem itself, it is written into the superblock. Since Fog 1.2.0 fog also seems to allow UUIDs in /etc/fstab for swap partitions. For other filesystems, I’m not sure, I haven’t noticed any problems with xfs, but I haven’t looked too close. Incidentally, there are some other reasons to use ext4 - fog 1.2.0 can resize ext4 filesystems automatically!

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                                    • H
                                      Hongyun
                                      last edited by

                                      [quote=“ianabc, post: 34153, member: 24548”]UUIDs work for ext3 and ext4 filesystems because the UUID is part of the filesystem itself, it is written into the superblock. Since Fog 1.2.0 fog also seems to allow UUIDs in /etc/fstab for swap partitions. For other filesystems, I’m not sure, I haven’t noticed any problems with xfs, but I haven’t looked too close. Incidentally, there are some other reasons to use ext4 - fog 1.2.0 can resize ext4 filesystems automatically![/quote]
                                      But I think the problem now is that after downloading the FOG image, the swap partition’s UUID got changed, even when I download the image to the same computer where I uploaded the image from. Our instructor prefer the Mageia 4.1, I’m still trying to make this work with FOG, a month left before the term starts, feeling the pressure now:(

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                                      • I
                                        ianabc Testers
                                        last edited by

                                        From the image you showed above, are you sure that swap is the problem? what filesystems are your other partitions on? swap problems shouldn’t stop a system from booting in general - as I might have said above, it’s just swap!

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                                        • I
                                          ianabc Testers
                                          last edited by

                                          Actually it looks like mageia (and some fedora) might have an issue with swap UUIDs. Somebody thought that putting UUIDs into initramfs was a good idea. There are some workarounds, but I don’t have any machines to work with to try them out.

                                          [LIST]
                                          [][url]https://forums.mageia.org/en/viewtopic.php?f=7&t=7093[/url]
                                          [
                                          ][url]http://forums.fedoraforum.org/showthread.php?t=292088[/url]
                                          [/LIST]
                                          Additionally, when an instructor - or anyone for that matter - asks for a specific distribution, it is a good idea to ask them what they are intending to do with it. Unless they are working with the package manager(s) day to day it generally doesn’t matter. Usually they have conflated a specific set of applications and versions with an distribution.

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                                          • I
                                            ianabc Testers
                                            last edited by

                                            Could you take a look in /images/NAMEOFYOURIMAGE and see if you can find a file similar to “d1.original.swapuuids”. Here is one of mine
                                            [CODE]
                                            $ cat /images/RHL7x64PIMS50GBResizeable/d1.original.swapuuids
                                            /dev/sda5 7f6a8920-bab3-444d-8e3f-acca4c76e3cd
                                            [/CODE]
                                            When I deploy that image to a machine the UUID of the swap partition matches
                                            [CODE]
                                            $ blkid /dev/sda5 UUID=“7f6a8920-bab3-444d-8e3f-acca4c76e3cd”
                                            [/CODE]
                                            Obviously, change /dev/sda5 to wherever your swap partition is.

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