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Live snapshots with Virtual Machine Manager
Snapshots
Virtual machine snapshots are practically an indispensable part of the system administrator's everyday life. A snapshot freezes the state of a virtual machine and writes it to disk. Snapshots are useful for a variety of tasks, depending on the application and the type. For example, snapshots let you repeatedly restore the original state of a virtual machine without having to create multiple VMs. A recovery point generated via a snapshot thus retains the initial state, before a developer or admin makes further changes to the VM. This explains why developers really like using snapshots.
Snapshots are also a useful tool for patching applications or servers. Thus, administrators like to use snapshots when they suspect a configuration error or see signs of the imminent demise of a hardware component. If you suspect a break-in or need to secure proof in forensic investigations, a VM snapshot can be a useful tool. Admins also can, for example, use VM checkpointing to create as many snapshots of their VM – including multiple restore points – as needed.
Internal and External Snapshots
The different types of snapshots also differ in terms of whether the RAM state and the filesystem of the VM are frozen. All well-known virtualization solutions today support snapshots. In this article, I cover the kind of snapshots provided by the Linux libvirt abstraction layer, especially those that can be used in the graphical front end, Virtual Machine Manager (VMM) [1].
In general, Qemu [2] or libvirt [3] distinguish between internal and external snapshots. For internal snapshots, libvirt freezes the complete state of the current virtual machine and writes the snapshot directly to the image file of the virtual disk. This includes the
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