July 2025 - Users - Libvirt List Archives

Re: Clarification Needed: virsh snapshot-delete Behavior with External Snapshots (--disk-only)

by Peter Krempa

On Wed, Jul 23, 2025 at 04:57:57 +0000, P, Rajasekar via Users wrote: > Hello libvirt community, > > I am seeking clarification on the behavior of `virsh snapshot-delete` when used with external snapshots (created with the `--disk-only` option). > > **Environment:** > - libvirt version: 10.5.0 Note that this was released almost a year ago. > - Kernel version: 5.14.0-503.22.1.el9_5.x86_64 > - Disk image format: qcow2 > - Host OS: RHEL 9.5 > > **Steps to reproduce:** > 1. Create an external snapshot: > virsh snapshot-create-as --domain <vm> --name snap1 --disk-only --atomic > 2. Delete the snapshot: > virsh snapshot-delete <vm> --snapshotname snap1 > > **Observed behavior:** > - Changes from the overlay (snapshot) file are merged into the base image. > - The snapshot metadata is removed from libvirt. > - The snapshot file remains on disk (appears orphaned). You mean that the original overlay images remained on disk? e.g. /path/to/originalimage.snap1 ? > **Questions:** > - Is the observed automatic merge of the overlay file into the base image during `snapshot-delete` the intended behavior for external snapshots in recent libvirt versions? Or we need separate `blockcommit` step. Yes it is intended, because deleting a snapshot is effectively meaning "I don't want to return to this point any more" so the extra overlay makes no sense. > - Should the snapshot file be deleted automatically, or is manual cleanup required? If you mean the overlay, then yes it should have been deleted. > - Is there any official documentation that clarifies this behavior for external snapshots, as most documentation seems to focus on internal snapshots? The semantics of external and internal snapshots are supposed to be indentical. I don't think we document to a deep extent the actual behaviour WRT to the disk files.

2 weeks, 5 days

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Clarification Needed: virsh snapshot-delete Behavior with External Snapshots (--disk-only)

by P, Rajasekar

Hello libvirt community, I am seeking clarification on the behavior of `virsh snapshot-delete` when used with external snapshots (created with the `--disk-only` option). **Environment:** - libvirt version: 10.5.0 - Kernel version: 5.14.0-503.22.1.el9_5.x86_64 - Disk image format: qcow2 - Host OS: RHEL 9.5 **Steps to reproduce:** 1. Create an external snapshot: virsh snapshot-create-as --domain <vm> --name snap1 --disk-only --atomic 2. Delete the snapshot: virsh snapshot-delete <vm> --snapshotname snap1 **Observed behavior:** - Changes from the overlay (snapshot) file are merged into the base image. - The snapshot metadata is removed from libvirt. - The snapshot file remains on disk (appears orphaned). **Questions:** - Is the observed automatic merge of the overlay file into the base image during `snapshot-delete` the intended behavior for external snapshots in recent libvirt versions? Or we need separate `blockcommit` step. - Should the snapshot file be deleted automatically, or is manual cleanup required? - Is there any official documentation that clarifies this behavior for external snapshots, as most documentation seems to focus on internal snapshots? Thank you for your help and clarification! Best regards, Raj.

3 weeks

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Hanging migration leaving domain in paused state

by Yangchen Ye

Hi, We are running libvirt 8.0.0, and sometimes live migration could not finish (because the guest is dirtying the memory too fast). We implemented a monitor that increases max downtime when it observed that "Data Remaining" bumps up. But we found a strange sequence of events from the monitor, which leads to a paused domain on the destination hypervisor: The monitor sees Data Remaining bumping up and increases max downtime up to 20 seconds, but weird thing is that after a period of time, it started reporting "Data Remaining" and "Data Total" is both 0, but the migration job is still unfinished: "Migration in progress - DataTotal: 85 904728064, DataRemaining: 22201458688, TimeElapsed: 20005, MaxDowntime: 500, DirtyRate: 0" "Migration in progress - DataTotal: 85904728064, DataRemaining: 43801825280, TimeElapsed: 10005, MaxDowntime: 500, DirtyRate: 0" "Migration in progress - DataTotal: 85904728064, DataRemaining: 52382912512, TimeElapsed: 10004, MaxDowntime: 500, DirtyRate: 0" (DataRemaining bumps up, we start increasing max downtime) "Migration in progress - DataTotal: 85904728064, DataRemaining: 4219596800, TimeElapsed: 40004, MaxDowntime: 1500, DirtyRate: 0" (Last poll where we see the job info) After which monitor logs "Migration in progress - DataTotal: 0, DataRemaining: 0, TimeElapsed: 40004, MaxDowntime: 13500, DirtyRate: 0" The domain is always running on the source hypervisor but there is a paused domain on the destination hypervisor which is paused at start up. Trying to understand what might have happened: - Is this a known issue for live migrating high memory activity guests and the way we interact with libvirt? - What is the recommended way to ensure that a started live migration always run to completion if we don't care about downtime? Appreciate any help here Yangchen Ye

3 weeks, 1 day

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How to recover from "Display output is not active"

by Jeffrey Walton

Hi Everyone, I'm working on Ubuntu 22.04.5, amd64, fully patched. It provides QEMU 1:6.2+dfsg-2ubuntu6.26 and libvirt 8.0.0-1ubuntu7.11. The problem I am experiencing is, when the host machine blanks the monitor, I lose the display on the guest when I sit back down at the computer and wake the monitor. The error message (?) in the guest window is, "Display output is not active." The condition happens with both VIRTIO and VGA models. Also see <https://imgur.com/a/tEp73k2>. I have not found a workaround to stop it from happening or recover after it happens. I have to Force Off the VM and then restart the VM to the display back. My host power configuration is: disable sleep, suspend, hibernate and hybrid-sleep via systemd's systemctl. However, I allow the monitor to be turned off after 15 minutes of inactivity. My guest power configuration is whatever the distro provides. Based on my searching, others have experienced the problem. And one fellow says switching to the VGA model fixed it for him. (But no joy for me). Does anyone have any suggestions for a work around? Thanks in advance. (And my apologies if this is the wrong list). Jeff

4 weeks, 1 day

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How to disable sysctl calls performed by libvirt?

by Chimmie Firefly

Hello, I have an issue whenever using `/proc/sys/ipv6/conf` as read-only mountpoint. While the libvirt by itself is running fine, I'm unable to create NAT network interfaces because of the following error: ``` 2025-07-05 19:33:32.821+0000: 100: error : networkSetIPv6Sysctl:1847 : cannot write to '/proc/sys/net/ipv6/conf/virbr0/disable_ipv6' on bridge 'virbr0': Read-only file system 2025-07-05 19:33:32.841+0000: 100: error : virNetDevSetIFFlag:601 : Cannot get interface flags on 'virbr0': No such device 2025-07-05 19:33:32.947+0000: 100: error : virNetlinkDelLink:688 : error destroying network device virbr0: No such device ``` While using iproute2 and bridge utils, I'm able to create and configure new bridge device, along with attaching the VM to the interface. I've used the following commands: ``` sysctl -w net.ipv4.ip_forward=1 brctl addbr br0 ip link set br0 up ip addr add 192.168.100.1/24 dev br0 iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE iptables -A FORWARD -i br0 -o eth0 -j ACCEPT iptables -A FORWARD -i eth0 -o br0 -m state --state RELATED,ESTABLISHED -j ACCEPT ``` Is libvirt allowing to disable sysctl calls in the configuration files? If so, what should I set in the config?

1 month

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List checkpoints

by francisco.garcia＠baculasystems.com

Hello, I'm using checkpoints to back up Libvirt domains. I'm using the "virsh backup-begin" tool and specifying the dombackup and checkpoint XML files. Everything works correctly (I perform full and incremental backups) without any issues. When I list the checkpoints using the "virsh checkpoint-list DOMAIN --parent --topological" tool, it correctly shows me the entire chain of full and incremental backups. However, when I perform a differential backup, setting the parent of that checkpoint to the last full checkpoint, I have problems when listing them. It tells me that the parent of the differential checkpoint is the last incremental checkpoint, instead of the full checkpoint. And I don't understand why, because when I perform the backup-begin, I specify the full checkpoint in the "incremental" label, and the bitmap generated from the disk is all the data from the full checkpoint on. I put the xmls that I used: FULL BACKUP: dombackup.xml: ``` <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <domainbackup mode="pull"> <server name="localhost" port="10809"/> <disks> <disk name="vda" type="file"> <scratch file="/tmp/libvirt-full-30-vda-debian12.scratch"/> </disk> <disk name="vdb" type="file"> <scratch file="/tmp/libvirt-full-30-vdb-debian12.scratch"/> </disk> </disks> </domainbackup> ``` checkpoint.xml ``` <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <domaincheckpoint> <name>Full-30-Debian12</name> <disks> <disk name="vda" bitmap="Full-30-Debian12" checkpoint="bitmap"/> <disk name="vdb" bitmap="Full-30-Debian12" checkpoint="bitmap"/> <disk name="sda" checkpoint="no"/> </disks> </domaincheckpoint> ``` -------------------------------------------------------- INCREMENTAL BACKUP: dombackup.xml ``` <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <domainbackup mode="pull"> <server name="localhost" port="10809"/> <incremental>Full-30-Debian12</incremental> <disks> <disk name="vda" type="file"> <scratch file="/tmp/libvirt-incremental-35-vda-debian12.scratch"/> </disk> <disk name="vdb" type="file"> <scratch file="/tmp/libvirt-incremental-35-vdb-debian12.scratch"/> </disk> </disks> </domainbackup> ``` checkpoint.xml ``` <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <domaincheckpoint> <name>Incremental-31-Debian12</name> <parent> <name>Full-30-Debian12</name> </parent> <disks> <disk name="vda" bitmap="Incremental-31-Debian12" checkpoint="bitmap"/> <disk name="vdb" bitmap="Incremental-31-Debian12" checkpoint="bitmap"/> <disk name="sda" checkpoint="no"/> </disks> </domaincheckpoint> ``` ----------------------------------------------------------------- DIFFERENTIAL BACKUP: dombackup.xml ``` <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <domainbackup mode="pull"> <server name="localhost" port="10809"/> <incremental>Full-30-Debian12</incremental> <disks> <disk name="vda" type="file"> <scratch file="/tmp/libvirt-differential-36-vda-debian12.scratch"/> </disk> <disk name="vdb" type="file"> <scratch file="/tmp/libvirt-differential-36-vdb-debian12.scratch"/> </disk> </disks> </domainbackup> ``` checkpoint.xml ``` <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <domaincheckpoint> <name>Differential-32-Debian12</name> <parent> <name>Full-30-Debian12</name> </parent> <disks> <disk name="vda" bitmap="Differential-32-Debian12" checkpoint="bitmap"/> <disk name="vdb" bitmap="Differential-32-Debian12" checkpoint="bitmap"/> <disk name="sda" checkpoint="no"/> </disks> </domaincheckpoint> ``` ----------------------------------------------------------------------- After apply several "virsh backup-begin" with these files: ``` virsh checkpoint-list debian12 --topological --parent Name Creation Time Parent -------------------------------------------------------------------------------------------------------------------------------- Full-30-Debian12 2025-07-09 17:08:31 +0200 Incremental-31-Debian12 2025-07-09 17:34:56 +0200 Full-30-Debian12 Differential-32-Debian12 2025-07-09 17:37:51 +0200 Incremental-31-Debian12 ``` I do not know why the parent of "Differential-32-Debian12" is "Incremental-31-Debian12" instead of "Full-30-Debian12". Any ideas?

1 month

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fsck unable to fix fs issue

by ola .

I am able to boot VMs by using rbd as the root disk. When I restart and stop the VM everything works fine however, anytime the host goes down say due to a power outage, when next I try to boot the VM, I run into a situation where the root disk gets corrupted and get stuck at "initramfs". I have tried to fix this but to no avail. Here are the errors I get when I try yo use fix the fs issue with fsck manually. done. Begin: Running /scripts/init-premount ... done. Begin: Mounting root file system ... Begin: Running /scripts/local-top ... done. Begin: Running /scripts/local-premount ... [ 7.760625] Btrfs loaded, crc32c=crc32c-intel, zoned=yes, fsverity=yes Scanning for Btrfs filesystems done. Begin: Will now check root file system ... fsck from util-linux 2.37.2 [/usr/sbin/fsck.ext4 (1) -- /dev/vda1] fsck.ext4 -a -C0 /dev/vda1 [ 7.866954] blk_update_request: I/O error, dev vda, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0 cloudimg-rootfs: recovering journal [ 8.164279] blk_update_request: I/O error, dev vda, sector 227328 op 0x1:(WRITE) flags 0x800 phys_seg 24 prio class 0 [ 8.168272] Buffer I/O error on dev vda1, logical block 0, lost async page write [ 8.170413] Buffer I/O error on dev vda1, logical block 1, lost async page write [ 8.172545] Buffer I/O error on dev vda1, logical block 2, lost async page write [ 8.174601] Buffer I/O error on dev vda1, logical block 3, lost async page write [ 8.176651] Buffer I/O error on dev vda1, logical block 4, lost async page write [ 8.178694] Buffer I/O error on dev vda1, logical block 5, lost async page write [ 8.180601] Buffer I/O error on dev vda1, logical block 6, lost async page write [ 8.182641] Buffer I/O error on dev vda1, logical block 7, lost async page write [ 8.184710] Buffer I/O error on dev vda1, logical block 8, lost async page write [ 8.186744] Buffer I/O error on dev vda1, logical block 9, lost async page write [ 8.188748] blk_update_request: I/O error, dev vda, sector 229392 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 8.191433] blk_update_request: I/O error, dev vda, sector 229440 op 0x1:(WRITE) flags 0x800 phys_seg 32 prio class 0 [ 8.194204] blk_update_request: I/O error, dev vda, sector 229480 op 0x1:(WRITE) flags 0x800 phys_seg 16 prio class 0 [ 8.196976] blk_update_request: I/O error, dev vda, sector 229512 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 8.243612] blk_update_request: I/O error, dev vda, sector 229544 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 8.246068] blk_update_request: I/O error, dev vda, sector 229640 op 0x1:(WRITE) flags 0x800 phys_seg 32 prio class 0 [ 8.248668] blk_update_request: I/O error, dev vda, sector 229688 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 8.251174] blk_update_request: I/O error, dev vda, sector 229704 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 fsck.ext4: Input/output error while recovering journal of cloudimg-rootfs fsck.ext4: unable to set superblock flags on cloudimg-rootfs cloudimg-rootfs: ********** WARNING: Filesystem still has errors ********** fsck exited with status code 12 done. Failure: File system check of the root filesystem failed The root filesystem on /dev/vda1 requires a manual fsck BusyBox v1.30.1 (Ubuntu 1:1.30.1-7ubuntu3.1) built-in shell (ash) Enter 'help' for a list of built-in commands. (initramfs) fsck.ext4 -f -y /dev/vda1 e2fsck 1.46.5 (30-Dec-2021) [ 24.286341] print_req_error: 174 callbacks suppressed [ 24.286358] blk_update_request: I/O error, dev vda, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0 cloudimg-rootfs: recovering journal [ 24.552343] blk_update_request: I/O error, dev vda, sector 227328 op 0x1:(WRITE) flags 0x800 phys_seg 24 prio class 0 [ 24.556674] buffer_io_error: 5222 callbacks suppressed [ 24.558925] Buffer I/O error on dev vda1, logical block 0, lost async page write [ 24.562116] Buffer I/O error on dev vda1, logical block 1, lost async page write [ 24.565161] Buffer I/O error on dev vda1, logical block 2, lost async page write [ 24.567872] Buffer I/O error on dev vda1, logical block 3, lost async page write [ 24.570586] Buffer I/O error on dev vda1, logical block 4, lost async page write [ 24.573418] Buffer I/O error on dev vda1, logical block 5, lost async page write [ 24.575940] Buffer I/O error on dev vda1, logical block 6, lost async page write [ 24.578622] Buffer I/O error on dev vda1, logical block 7, lost async page write [ 24.581386] Buffer I/O error on dev vda1, logical block 8, lost async page write [ 24.583873] Buffer I/O error on dev vda1, logical block 9, lost async page write [ 24.586410] blk_update_request: I/O error, dev vda, sector 229392 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 24.589821] blk_update_request: I/O error, dev vda, sector 229440 op 0x1:(WRITE) flags 0x800 phys_seg 32 prio class 0 [ 24.593380] blk_update_request: I/O error, dev vda, sector 229480 op 0x1:(WRITE) flags 0x800 phys_seg 16 prio class 0 [ 24.596615] blk_update_request: I/O error, dev vda, sector 229512 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 24.643829] blk_update_request: I/O error, dev vda, sector 229544 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 24.646924] blk_update_request: I/O error, dev vda, sector 229640 op 0x1:(WRITE) flags 0x800 phys_seg 32 prio class 0 [ 24.650051] blk_update_request: I/O error, dev vda, sector 229688 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 [ 24.653128] blk_update_request: I/O error, dev vda, sector 229704 op 0x1:(WRITE) flags 0x800 phys_seg 8 prio class 0 fsck.ext4: Input/output error while recovering journal of cloudimg-rootfs fsck.ext4: unable to set superblock flags on cloudimg-rootfs cloudimg-rootfs: ********** WARNING: Filesystem still has errors ********** This is what my rbd disk looks like <disk type='network' device='disk'> <driver name='qemu' type='raw' cache='none' io='native'/> <auth username='dove'> <secret type='ceph' uuid='b608caae-5eb4-45cc-bfd4-0b4ac11c7613'/> </auth> <source protocol='rbd' name='vms/wing-64700f1d-8c469a54-3f50-4d1e-9db2-2b6ea5f3d14a'> <host name='x.168.1.x' port='6789'/> </source> <target dev='vda' bus='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </disk> So, my questions are; - How do I prevent this from happening as i have tried different options like changing the "cache" value for the disk template? - How can this be fixed? Thanks

1 month

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