Re: [libvirt-users] virsh uses internally qemu-img ?

On Mon, Nov 30, 2015 at 01:57:24AM +0100, Lentes, Bernd wrote: Functionally, it is the same. However: Snapshotting of guests using `virsh` will let libvirt track the life-cycle of the snapshot and management/revert/clean-up of snapshots is easier. The `qemu-img` command: $ qemu-img snapshot -c snap1 f23vm.qcow2 [And, to your question: "Will the above command harm the running VMs filesystem ?", it depends on what is running inside your guest. To ensure you have a consistent guest disk state, use the qemu-guest-agent inside the guest, and supply the '--quiesce' flag to `virsh-snapshot-create-as` command. See [1] Maps to `virsh`: $ virsh snapshot-create-as f23vm snap1 "Clean F23" This results in: - The original and the delta (the snaphot) will be stored in the same qcow2 file (f23vm.qcow2). These type of snapshots are called 'internal snapshots' -- these are possible only with qcow2 format. - The guest _will_ be paused briefly. - Libvirt tracking the snapshot status of the guest. If you want to have snapshots without any guest downtime, you can use the more robust 'external snapshots', which operates differently: when a snapshot is taken, a _new_ qcow2 file is created, which will track the new guest writes from there on. And, the old image will become read-only backing file. Some more context on it here[2]. These type of snapshots can be performed using the 'qemu-kvm-ev' packages, which you can obtain from the oVirt repositories http://resources.ovirt.org/pub/ovirt-master-snapshot/rpm/el7/x86_64/ Or from the CentOS build system: http://cbs.centos.org/koji/packageinfo?packageID=539 Ideally these should be available in a repository, but I can't find one at the moment. [1] http://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit [2] http://wiki.libvirt.org/page/I_created_an_external_snapshot%2C_but_libvir... -- /kashyap