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+++ This bug was initially created as a clone of Bug #1402581 +++
Description of problem:
For historical reasons, 'virsh snapshot-create' defaults to internal snapshots, because external snapshots were not implemented for several years. However, these days the qemu team recommends the use of external snapshots, and upper levels like RHEV prefer external snapshots. It would be nice if there were a way to set up configuration defaults for virsh, so that typing 'virsh snapshot-create' could consult the configuration file on whether to default to internal or external, instead of forcing the user to remember to pass extra flags to get an external snapshot.
Version-Release number of selected component (if applicable):
libvirt-2.5.0-1.el7
How reproducible:
100%
Steps to Reproduce:
1.
2.
3.
Actual results:
Expected results:
Additional info:
--- Additional comment from Laszlo Ersek on 2017-02-24 20:50:15 BRT ---
When designing this feature for virsh (and virt-manager), please don't forget about the UEFI varstore files (under /var/lib/libvirt/qemu/nvram), which are technically raw drives, but have very different storage properties from normal drives. They don't live in storage pools, they are not on shared storage, and also not subject to storage migration. QEMU automatically writes them out fully on the target host after migration finishes.
I'm unsure how this interacts with external snapshots, but I figure I'd better raise it. Thanks.
There are multiple options how to create an external snapshot:
1) using virsh snapshot-create-as (see man page for further explanation):
1.1) if the VM is active, but the user doesn't want to take a snapshot of the memory
virsh snapshot-create-as $VMNAME --disk-only
1.2) if the vm is active and memory snapshot is required
virsh snapshot-create-as $VMNAME --memspec file=/path/to/memory-image,snapshot=external
1.3) if disks which take part of the snapshot need to be controlled:
virsh snapshot-create-as $VMNAME --memspec file=/path/to/memory-image,snapshot=external --diskspec vda,snapshot=no --diskspec vdb,file=/path/to/overlay-img
1.4) any additional options such as snapshot name, description etc can be controlled using additional parameters. Please refer to the man page:
https://libvirt.org/manpages/virsh.html#snapshot-create-as
2) using virsh snapshot create
This option requires an XML document describing the snapshot as argument. Please refer to the documentation.
For inspiration, a sample XML can be obtained using the '--print-xml' argument for 'virsh snapshot-create-as' which prints the XML the command generates.
snapshot XML documentation:
https://libvirt.org/formatsnapshot.html
Please note, that while creating external snapshots works, we don't yet have implementation for reverting or deleting external snapshots, thus internal snapshots must be supported until then.
Regarding customer's question, rhel-7.6 already supports external snapshots to the extent above.
If required there are manual steps which allow reversion or deletion of external snapshots.
Comment 29RHEL Program Management
2023-09-22 17:50:43 UTC
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.
Comment 30RHEL Program Management
2023-09-22 17:51:33 UTC
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