snapshot
also: snapshot volume, LVM snapshot
A point-in-time copy of a filesystem or volume that captures its state at a specific moment, allowing you to restore data or create backups without duplicating all storage space.
A snapshot is a read-only or read-write copy of a filesystem at a particular point in time. Modern filesystems like Btrfs and LVM (Logical Volume Manager) support snapshots through copy-on-write technology, where only changes after the snapshot are stored separately, making snapshots fast and space-efficient.
Snapshots are commonly used for backups, testing, and recovery. For example, you might create a snapshot before a risky system update, then quickly revert if something breaks. In containerized environments, snapshots preserve the state of images and running containers.
Example with LVM: lvcreate -L 1G -s -n backup /dev/vg0/data creates a 1GB snapshot named 'backup' of the logical volume 'data'. Unlike a full backup, only 1GB of new storage is needed, not a complete copy.