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    VM failed and won't start. Displaying "An emulator required to run this VM failed to start"

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    • R Offline
      rustylh
      last edited by olivierlambert

      AlmaLinux 8.10. VM failed and won't start. Displaying "An emulator required to run this VM failed to start".
      I have restarted the toolstack on the Host Server. I have attempted to create snapshot and revert. Any help is appreciated.

      I just tried to migrate a test VM to the same host. No getting.

      "Failed","Migrating VM 'AlmaLinux8-Testing' from 'iahost-xcpng-server3' to 'iahost-xcpng-server1'
      Internal error: xenopsd internal error: Xenops_interface.Xenopsd_error([S(Storage_backend_error);[S(SR_BACKEND_FAILURE_46);[S();S(The VDI is not available [opterr=Command ['/sbin/lvs', '--noheadings', '--units', 'b', '-o', '+lv_tags', '/dev/VG_XenStorage-88d7607c-f807-3b06-6f70-2dcb319d97ea'] failed (5): /dev/sdb: open failed: No such device or address
        Volume group "VG_XenStorage-88d7607c-f807-3b06-6f70-2dcb319d97ea" not found
        Cannot process volume group VG_XenStorage-88d7607c-f807-3b06-6f70-2dcb319d97ea]);S()]]])
      Time: 00:09:43","iahost-xcpng-server1","Jun 9, 2025 10:41 AM"
      

      And now attempting to force a reboot on same vm

      "Failed","Rebooting VM 'AlmaLinux8-Testing' on 'iahost-xcpng-server3'
      Internal error: Object with type VM and id dfcdcce6-b6e1-d865-6f2b-472a35b1fae7/config does not exist in xenopsd
      Time: 00:00:01","iahost-xcpng-server3","Jun 9, 2025 11:03 AM"
      
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      • olivierlambertO Online
        olivierlambert Vates 🪐 Co-Founder CEO
        last edited by olivierlambert

        /dev/sdb: open failed

        That's your issue. Can you check if your SR is correctly connected? Are you using Qcow alpha?

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        • R Offline
          rustylh @olivierlambert
          last edited by

          @olivierlambert said in VM failed and won't start. Displaying "An emulator required to run this VM failed to start":

          Qcow alpha

          No Qcow alpha. I do have three other host with no issues that I know of (Hopfully) attached is the Storage Screenshot on that host.SR Image.png

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          • olivierlambertO Online
            olivierlambert Vates 🪐 Co-Founder CEO
            last edited by

            Check the SR view in XO, hosts tab to see if they are all connected.

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            • R Offline
              rustylh @olivierlambert
              last edited by

              @olivierlambert SR View.png

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              • olivierlambertO Online
                olivierlambert Vates 🪐 Co-Founder CEO
                last edited by

                Do a lsblk on the problematic host, let's see what's /dev/sdb

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                • R Offline
                  rustylh @olivierlambert
                  last edited by

                  @olivierlambert lsblk.png

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                  • olivierlambertO Online
                    olivierlambert Vates 🪐 Co-Founder CEO
                    last edited by

                    So first, how does "AlmaLinux8-Testing" appear in XO? Like started? If it's the case, you might do a state power reset to it. Then, check the dmesg on the host, I have a feeling there's a connection issue with it.

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                    • R Offline
                      rustylh @olivierlambert
                      last edited by

                      @olivierlambert "Failed","Shutting down VM 'AlmaLinux8-Testing' on 'iahost-xcpng-server3'
                      Internal error: Object with type VM and id dfcdcce6-b6e1-d865-6f2b-472a35b1fae7/config does not exist in xenopsd","iahost-xcpng-server3","Jun 9, 2025 12:28 PM"

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                      • olivierlambertO Online
                        olivierlambert Vates 🪐 Co-Founder CEO
                        last edited by

                        That's why you need to power reset it first.

                        Also please check the host dmesg

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                        • R Offline
                          rustylh @olivierlambert
                          last edited by

                          @olivierlambert Oh, I'm sorry. You mean power restart the host server?

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                          • R Offline
                            rustylh @rustylh
                            last edited by

                            [12:52 iahost-xcpng-server3 ~]# xe vm-reset-powerstate vm=dfcdcce6-b6e1-d865-6f2b-472a35b1fae7 --force
                            This operation cannot be completed because the server is still live.
                            host: 6985c3a2-091d-488b-8de6-4bf40985987b (iahost-xcpng-server3)

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                            • olivierlambertO Online
                              olivierlambert Vates 🪐 Co-Founder CEO
                              last edited by

                              On the pool master:

                              1. Restart the toolstack
                              2. Immediately after, run the vm reset powerstate command.
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                              • R Offline
                                rustylh @olivierlambert
                                last edited by

                                @olivierlambert Ok. I was able to get that VM started on another Host. Now, I need to figure out what is going on with server1. I appreciate all your help! If you have any suggestions please let me know.

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                                • olivierlambertO Online
                                  olivierlambert Vates 🪐 Co-Founder CEO
                                  last edited by

                                  My suggestion stands from previous messages, check the dmesg output from the problematic host 🙂

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                                  • R Offline
                                    rustylh @olivierlambert
                                    last edited by

                                    @olivierlambert It is full of these:
                                    43342477.643853] sd 7:0:0:1: rejecting I/O to offline device
                                    [43342477.643861] print_req_error: I/O error, dev sdb, sector 0

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                                    • olivierlambertO Online
                                      olivierlambert Vates 🪐 Co-Founder CEO
                                      last edited by

                                      That's exactly what I suspected. You have a connectivity issue with your shared storage.

                                      The device is considered offline because it cannot do any I/O on sector 0

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                                      • R Offline
                                        rustylh
                                        last edited by

                                        said in VM failed and won't start. Displaying "An emulator required to run this VM failed to start":

                                        rejecting I/O to offline device

                                        I was able to reboot the host. Now things seam fine. Does that make sense? I mean have you seen this happen then a reboot of the host takes care of it?

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                                        • R Offline
                                          rustylh @olivierlambert
                                          last edited by

                                          @olivierlambert I had the same issue this morning on one of the hosts I rebooted and was working fine. An emulator required to run this VM Failed to start. sd 7:0:0:1: rejecting I/O to offline device. I am not sure what to check next.

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                                          • R Offline
                                            rustylh
                                            last edited by

                                            xcp-ng iscsiadm -m session -P 3 Attached scsi disk sdb State: offline

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