# 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