What is a backup snapshot?
A snapshot is a frozen picture of a disk or system at one moment that you can roll back to if something goes wrong.
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A snapshot captures the exact state of a disk, volume or virtual machine at a point in time. It is like pressing pause and taking a photograph: the system keeps running, but you can always return to that photo. Most storage systems make snapshots almost instantly by recording only what changes afterwards, so they are cheap to take.
You take one before a risky upgrade, a database migration or a configuration change, and roll back in seconds if it fails. Proxmox, ZFS, Btrfs, LVM and every cloud provider offer them. A snapshot is not a full backup: it lives on the same storage as the original, so a dead disk takes both. Real backups copy data to a different place.
zfs snapshot tank/data@before-upgrade
qm snapshot 100 pre-upgradeSee also: What is RAID? and What is a virtual machine?
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See also
- 0362 The 3-2-1 backup rule, and why a backup you never restored is not a backup Three copies, two kinds of media, one off-site: what the rule really protects against, how it maps to real tools, and why… Beginner · Explains an idea · Any system Article Strategy & restore drills 15 Oct 2026
- 0363 Restore drill: prove your backup works in 15 minutes A repeatable procedure to restore one file and one database from your newest backup into a scratch location, compare the result with… Intermediate · Step by step · Linux, macOS Article Backup tools · Strategy & restore drills 15 Oct 2026
- 0367 verify-latest-backup: alert when the newest dump is too old or too small A read-only bash check that finds the newest file in a backup directory, compares its age and size against limits, optionally tests… Beginner · Step by step · Linux Script Backups & syncing · Strategy & restore drills 15 Oct 2026
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