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VM Snapshots

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19 hours ago, SimonF said:

Trying to reproduce, created a VM on UD, but work ok for me.

image.png

I will try again tonight. This time with all the VMs turned off and not only the one that had the snapshot.

Could you let me know what the "pivot" option does?

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  • I have a NVME cache drive I use to hold my VMs, very close to capacity. So when I go to create a snapshot I get a storage error as I no extra space on the NVME to store 'said' snapshot. Is there the a

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4 hours ago, impoftheperverse said:

I will try again tonight. This time with all the VMs turned off and not only the one that had the snapshot.

Could you let me know what the "pivot" option does?

pivot means that it will wait for the data be added into original file and when complete change the VM to that file and remove the overlay.

On 6/23/2025 at 6:13 PM, SimonF said:

pivot means that it will wait for the data be added into original file and when complete change the VM to that file and remove the overlay.

I tried again and it was successful. The only difference with the previous attempt was that this time all the VMs were turned off. The time it failed, the VM that was turned on was using the 2 USB devices attached to the VM that had the snapshot. Probably it did not have anything to do, but just in case someone has the same issue, it's worth trying.

Thanks a lot for your help, SimonF.

  • 2 months later...

Can't revert snapshot on Win11 or Ubuntu VMs. Trying to do so while the VMs are running kills them instantly, and trying to do the same while they are off ends up in a spinner that never resolves (does nothing). Trying this with memory dump enabled on Q35-9.2 + OVMF VMs. It looks like the post request to VMajax.php fails with 500 Internal Server Error.

Edited by realies

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1 hour ago, realies said:

Can't revert snapshot on Win11 or Ubuntu VMs. Trying to do so while the VMs are running kills them instantly, and trying to do the same while they are off ends up in a spinner that never resolves (does nothing). Trying this with memory dump enabled on Q35-9.2 + OVMF VMs. It looks like the post request to VMajax.php fails with 500 Internal Server Error.

Which OS version are you running and could you provide Diagnostics?

  • 1 month later...

I've been trying to clean up my snapshots. I understand that I need to "block commit" in most cases (sometimes I can simply delete).

I've got a handful of snapshots now on different VMs where I get the following error and I am stumped:

virsh blockcommit '[vm name]'
  --path '/mnt/user/virtualmachines/[vm name]/vdisk1.img'
  --verbose
  --pivot
  --delete

/mnt/user/virtualmachines/[vm name]/vdisk1.img: error: invalid argument: could not find base image in chain for 'hdc'. .

The command failed.

I saw the similar issue in the previous posts, but I don't have USB attached to any of these VMs. The only commonality is that these machines all had multiple snapshots - the first block commit will work, but subsequent fail with this error.

Edited by autumnwalker

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14 hours ago, autumnwalker said:

I've been trying to clean up my snapshots. I understand that I need to "block commit" in most cases (sometimes I can simply delete).

I've got a handful of snapshots now on different VMs where I get the following error and I am stumped:

virsh blockcommit '[vm name]'
  --path '/mnt/user/virtualmachines/[vm name]/vdisk1.img'
  --verbose
  --pivot
  --delete

/mnt/user/virtualmachines/[vm name]/vdisk1.img: error: invalid argument: could not find base image in chain for 'hdc'. .

The command failed.

I saw the similar issue in the previous posts, but I don't have USB attached to any of these VMs. The only commonality is that these machines all had multiple snapshots - the first block commit will work, but subsequent fail with this error.

Can you provide the following information for me.

Lets start with one VM.

cat /etc/libvirt/qemu/snapshotdb/VM Name/snapshots.db

ls /mnt/user/domain/VM Name

8 hours ago, SimonF said:

Can you provide the following information for me.

Lets start with one VM.

cat /etc/libvirt/qemu/snapshotdb/VM Name/snapshots.db

ls /mnt/user/domain/VM Name

cat /etc/libvirt/qemu/snapshotdb/Graylog/snapshots.db
{
    "updates-2025-05-30": {
        "name": "updates-2025-05-30",
        "parent": "Base",
        "state": "disk-snapshot",
        "desc": null,
        "memory": {
            "@attributes": {
                "snapshot": "no"
            }
        },
        "creationtime": "1748623874",
        "method": "QEMU",
        "backing": {
            "hdc": [
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.updates-2025-05-30qcow2",
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.img"
            ],
            "rhdc": [
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.img",
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.updates-2025-05-30qcow2"
            ]
        },
        "primarypath": "\/mnt\/cache\/virtualmachines\/Graylog",
        "disks": [
            {
                "@attributes": {
                    "name": "hdc",
                    "snapshot": "external",
                    "type": "file"
                },
                "driver": {
                    "@attributes": {
                        "type": "qcow2"
                    }
                },
                "source": {
                    "@attributes": {
                        "file": "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.updates-2025-05-30qcow2"
                    }
                }
            }
        ]
    },
    "graylog_upgrade_6.2": {
        "name": "graylog_upgrade_6.2",
        "parent": "updates-2025-05-30",
        "state": "disk-snapshot",
        "desc": null,
        "memory": {
            "@attributes": {
                "snapshot": "no"
            }
        },
        "creationtime": "1749133567",
        "method": "QEMU",
        "backing": {
            "hdc": [
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.graylog_upgrade_6.2qcow2",
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.updates-2025-05-30qcow2",
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.img"
            ],
            "rhdc": [
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.img",
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.updates-2025-05-30qcow2",
                "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.graylog_upgrade_6.2qcow2"
            ]
        },
        "primarypath": "\/mnt\/cache\/virtualmachines\/Graylog",
        "disks": [
            {
                "@attributes": {
                    "name": "hdc",
                    "snapshot": "external",
                    "type": "file"
                },
                "driver": {
                    "@attributes": {
                        "type": "qcow2"
                    }
                },
                "source": {
                    "@attributes": {
                        "file": "\/mnt\/user\/virtualmachines\/Graylog\/vdisk1.graylog_upgrade_6.2qcow2"
                    }
                }
            }
        ]
    }
}

ls /mnt/user/virtualmachines/Graylog
graylog_upgrade_6.2.running  remove\ landscape.running  updates-2025-05-30.running  vdisk1.img*
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13 minutes ago, autumnwalker said:
 remove\ 

What is this? is just a file?

4 minutes ago, SimonF said:

What is this? is just a file?

It's actually the name of that file "remove\ landscape.running".

"remove landscape" was the name of the snapshot. It is the one that I successfully commit before running into the issue with committing "upgrade" and "updates" snapshots.

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14 hours ago, autumnwalker said:

It's actually the name of that file "remove\ landscape.running".

"remove landscape" was the name of the snapshot. It is the one that I successfully commit before running into the issue with committing "upgrade" and "updates" snapshots.

Can you provide output of

virsh dumpxml Graylog | xmllint --xpath '//devices/disk' -

10 hours ago, SimonF said:

Can you provide output of

virsh dumpxml Graylog | xmllint --xpath '//devices/disk' -

virsh dumpxml Graylog | xmllint --xpath '//devices/disk' -
-:5: namespace warning : xmlns: URI unraid is not absolute
    <vmtemplate xmlns="unraid" name="Ubuntu" icon="graylog.png" os="ubuntu" icon
                              ^
<disk type="file" device="disk">
      <driver name="qemu" type="raw" cache="writeback" discard="ignore"/>
      <source file="/mnt/user/virtualmachines/Graylog/vdisk1.img" index="4"/>
      <backingStore/>
      <target dev="hdc" bus="virtio"/>
      <boot order="1"/>
      <alias name="virtio-disk2"/>
      <address type="pci" domain="0x0000" bus="0x03" slot="0x00" function="0x0"/>
    </disk>
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On 10/23/2025 at 6:37 PM, autumnwalker said:

virsh dumpxml Graylog | xmllint --xpath '//devices/disk' -
-:5: namespace warning : xmlns: URI unraid is not absolute
    <vmtemplate xmlns="unraid" name="Ubuntu" icon="graylog.png" os="ubuntu" icon
                              ^
<disk type="file" device="disk">
      <driver name="qemu" type="raw" cache="writeback" discard="ignore"/>
      <source file="/mnt/user/virtualmachines/Graylog/vdisk1.img" index="4"/>
      <backingStore/>
      <target dev="hdc" bus="virtio"/>
      <boot order="1"/>
      <alias name="virtio-disk2"/>
      <address type="pci" domain="0x0000" bus="0x03" slot="0x00" function="0x0"/>
    </disk>

So looks like the VM is using the vdisk1 image not sure why the snapshotdb has not been updated when you completed the actions.

.running files are backups of the config at the point of snapshots. You can delete these if required.

Also you should be able to remove the snapshotdb file to remove the entries from the gui.

I will look into reasons why this may not have actioned as expected.

2 hours ago, SimonF said:

So looks like the VM is using the vdisk1 image not sure why the snapshotdb has not been updated when you completed the actions.

.running files are backups of the config at the point of snapshots. You can delete these if required.

Also you should be able to remove the snapshotdb file to remove the entries from the gui.

I will look into reasons why this may not have actioned as expected.

So from terminal I can, for example, rm -r /etc/libvirt/qemu/snapshotdb/Graylog/snapshots.db while the VM is running and also remove the .running files?

  • 2 weeks later...
On 10/27/2025 at 1:00 PM, autumnwalker said:

So from terminal I can, for example, rm -r /etc/libvirt/qemu/snapshotdb/Graylog/snapshots.db while the VM is running and also remove the .running files?

Just to report back / confirm - I did a rm -r *.running in each of the virtual machine folders and I did rm -r snapshots.db under /etc/libvirt/qemu/snapshotdb/[machine name]and everything worked as expected.

Thank you!

  • 6 months later...

Can someone tell me what the status is of snapshots on 7.3? I have a VM we tried to take a snapshot of today and it offered me the FS Native snapshot using ZFS.

A snapshot was created and listed. We tried to revert it, and sure enough it disappeared. But the VM did not revert and no changes were rolled back.

What gives? The Domains share is on the ZFS pool. It's a VM using qcow2. Is this not supported and just...silently breaks?

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