I'm on Fedora Linux 42.20250824.0 (Sway Atomic), running libvirt version 11.0.0, qemu-img version 9.2.4 (qemu-9.2.4-1.fc42) and virt-manager version 5.0.0, all installed as layered packages.
Using only virt-manager, I created a virtual machine and, at each step of my project, created a new external snapshot (which is the default type of snapshot for this version of virt-manager). Each snapshot was created with the VM completely shut down. At different times in the project, I had to revert to the current active snapshot. I ended up with 25 different snapshots.
Today, I tried running the VM and was presented with the following error:
# virsh start lab
error: Failed to start domain 'lab'
error: internal error: failed to parse JSON: nesting too deep
I searched on Google but wasn't able to find a solution for this particular problem. I then proceeded to investigate the possibility that 25 external snapshots was too much to handle for this version of libvirt.
Following this guide from libvirt, I tried to run the following command:
# virsh blockcommit lab vda --wait --verbose
error: invalid argument: could not find base image in chain for 'vda'
This error makes no sense to me, because from what I understand from the following commands, there is a base image in the chain for 'vda':
# virsh domblklist lab
Target Source
---------------------------------------------------------
vda /var/lib/libvirt/images/lab.1756116206
sda -
# qemu-img info --backing-chain /var/lib/libvirt/images/lab.1756116206
image: /var/lib/libvirt/images/lab.1756116206
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 216 KiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755873260
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1756116206
protocol type: file
file length: 216 KiB (220672 bytes)
disk size: 216 KiB
image: /var/lib/libvirt/images/lab.1755873260
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 20.4 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755867452
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755873260
protocol type: file
file length: 20.4 GiB (21891448832 bytes)
disk size: 20.4 GiB
image: /var/lib/libvirt/images/lab.1755867452
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 6.06 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.template-ready
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755867452
protocol type: file
file length: 6.06 GiB (6511656960 bytes)
disk size: 6.06 GiB
image: /var/lib/libvirt/images/lab.template-ready
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 16.5 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.prereqs
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.template-ready
protocol type: file
file length: 16.5 GiB (17696751616 bytes)
disk size: 16.5 GiB
image: /var/lib/libvirt/images/lab.prereqs
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 56.5 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755788922
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.prereqs
protocol type: file
file length: 56.5 GiB (60627877888 bytes)
disk size: 56.5 GiB
image: /var/lib/libvirt/images/lab.1755788922
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 3.68 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755720336
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755788922
protocol type: file
file length: 3.68 GiB (3950051328 bytes)
disk size: 3.68 GiB
image: /var/lib/libvirt/images/lab.1755720336
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 9.55 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755698841
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755720336
protocol type: file
file length: 9.55 GiB (10249568256 bytes)
disk size: 9.55 GiB
image: /var/lib/libvirt/images/lab.1755698841
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 26.4 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.websrv
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755698841
protocol type: file
file length: 26.4 GiB (28341895168 bytes)
disk size: 26.4 GiB
image: /var/lib/libvirt/images/lab.websrv
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 17.6 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.app1
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.websrv
protocol type: file
file length: 17.6 GiB (18863620096 bytes)
disk size: 17.6 GiB
image: /var/lib/libvirt/images/lab.app1
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 8.57 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.config
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.app1
protocol type: file
file length: 8.57 GiB (9205186560 bytes)
disk size: 8.57 GiB
image: /var/lib/libvirt/images/lab.config
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 25.6 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755527251
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.config
protocol type: file
file length: 25.6 GiB (27504672768 bytes)
disk size: 25.6 GiB
image: /var/lib/libvirt/images/lab.1755527251
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 27.3 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755513546
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755527251
protocol type: file
file length: 28.2 GiB (30260199424 bytes)
disk size: 27.3 GiB
image: /var/lib/libvirt/images/lab.1755513546
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 7.43 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755504820
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755513546
protocol type: file
file length: 7.43 GiB (7973240832 bytes)
disk size: 7.43 GiB
image: /var/lib/libvirt/images/lab.1755504820
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 25.3 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.extensions
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755504820
protocol type: file
file length: 25.3 GiB (27115257856 bytes)
disk size: 25.3 GiB
image: /var/lib/libvirt/images/lab.extensions
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 63.7 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1755111543
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.extensions
protocol type: file
file length: 63.7 GiB (68366303232 bytes)
disk size: 63.7 GiB
image: /var/lib/libvirt/images/lab.1755111543
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 307 MiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1754849159
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1755111543
protocol type: file
file length: 307 MiB (321650688 bytes)
disk size: 307 MiB
image: /var/lib/libvirt/images/lab.1754849159
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 13.8 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.packages
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1754849159
protocol type: file
file length: 13.8 GiB (14794686464 bytes)
disk size: 13.8 GiB
image: /var/lib/libvirt/images/lab.packages
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 15.5 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.pack03
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.packages
protocol type: file
file length: 15.5 GiB (16626810880 bytes)
disk size: 15.5 GiB
image: /var/lib/libvirt/images/lab.pack03
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 22.1 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.pack02
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.pack03
protocol type: file
file length: 22.1 GiB (23683596288 bytes)
disk size: 22.1 GiB
image: /var/lib/libvirt/images/lab.pack02
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 34.4 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.pack01
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.pack02
protocol type: file
file length: 34.4 GiB (36904042496 bytes)
disk size: 34.4 GiB
image: /var/lib/libvirt/images/lab.pack01
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 5.05 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.memory
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.pack01
protocol type: file
file length: 5.05 GiB (5422710784 bytes)
disk size: 5.05 GiB
image: /var/lib/libvirt/images/lab.memory
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 8.79 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.pre-inst
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.memory
protocol type: file
file length: 8.79 GiB (9437511680 bytes)
disk size: 8.79 GiB
image: /var/lib/libvirt/images/lab.pre-inst
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 19.7 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.1754779273
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.pre-inst
protocol type: file
file length: 19.7 GiB (21183266816 bytes)
disk size: 19.7 GiB
image: /var/lib/libvirt/images/lab.1754779273
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 135 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.stable
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.1754779273
protocol type: file
file length: 135 GiB (145155096576 bytes)
disk size: 135 GiB
image: /var/lib/libvirt/images/lab.stable
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 6.16 GiB
cluster_size: 65536
backing file: /var/lib/libvirt/images/lab.qcow2
backing file format: qcow2
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.stable
protocol type: file
file length: 6.16 GiB (6616383488 bytes)
disk size: 6.16 GiB
image: /var/lib/libvirt/images/lab.qcow2
file format: qcow2
virtual size: 1.46 TiB (1610612736000 bytes)
disk size: 3.55 GiB
cluster_size: 65536
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: true
refcount bits: 16
corrupt: false
extended l2: false
Child node '/file':
filename: /var/lib/libvirt/images/lab.qcow2
protocol type: file
file length: 1.47 TiB (1610858758144 bytes)
disk size: 3.55 GiB
Walking back the chain, it seems to me that there is a base image: /var/lib/libvirt/images/lab.qcow2
I also tried a different approach:
# virsh blockcommit --domain lab --path /var/lib/libvirt/images/lab.1756116206 --top /var/lib/libvirt/images/lab.1756116206 --base /var/lib/libvirt/images/lab.qcow2 --wait --verbose
error: invalid argument: could not find image '/var/lib/libvirt/images/lab.qcow2' beneath '/var/lib/libvirt/images/lab.1756116206' in chain for 'vda'
Each snapshot was an intermediate step, I don't really mind losing them to have a cleaner backing chain. However, I'd really like to be able to consolidate everything in a single image in order not to lose any of my work.
The situation now is less than ideal, I can start the VM if I revert to an older snapshot (for example /var/lib/libvirt/images/lab.1755720336), but:
- it makes me lose several day's worth of work
- since I don't know what caused the problem, there is no way for me to avoid it coming back
- I can't delete snapshots. When I try to do it:
# virsh snapshot-delete lab pack01
error: Failed to delete snapshot pack01
error: internal error: failed to parse JSON: nesting too deep
Can someone please guide me in further troubleshooting to better understand what happened and eventually find a way to save as much work as possible?
