Linux Kernel Module Cheat

23.5.1. Snapshot internals

Snapshots are stored inside the .qcow2 images themselves.

They can be observed with:

"$(./getvar buildroot_host_dir)/bin/qemu-img" info "$(./getvar qcow2_file)"

which after savevm my_snap_id and savevm asdf contains an output of type:

image: out/x86_64/buildroot/images/rootfs.ext2.qcow2
file format: qcow2
virtual size: 512M (536870912 bytes)
disk size: 180M
cluster_size: 65536
Snapshot list:
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         my_snap_id              47M 2018-04-27 21:17:50   00:00:15.251
2         asdf                    47M 2018-04-27 21:20:39   00:00:18.583
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

As a consequence:

it is possible to restore snapshots across boots, since they stay on the same image the entire time
it is not possible to use snapshots with initrd in our setup, since we don’t pass -drive at all when initrd is enabled