KVM Tools

Utilities for operating local KVM/libvirt virtual machines.

scripts/automatic-kvm-snapshots.sh creates timestamped libvirt snapshots for a fixed whitelist of VMs and prunes old snapshots after a new snapshot has been created and verified.

The script is intended for unattended runs from cron or systemd timers. It is defensive by default:

• runs with strict Bash settings
• uses flock to prevent overlapping runs
• validates required commands before touching VMs
• quotes all virsh arguments
• creates and verifies the new snapshot before pruning old cron snapshots
• keeps processing other whitelisted VMs when one VM fails
• exits nonzero when any VM snapshot operation fails

• Bash
• virsh from libvirt
• flock
• permissions to list VMs and manage snapshots for the target libvirt connection

The VM whitelist is currently defined in the script:

readonly -a VM_BACKUP_WHITELIST=("AlmaLinux-VM1" "AlmaLinux-VM2")

Runtime behavior can be adjusted with environment variables:

Snapshot names use the UTC format:

cronjob_YYYY_MM_DD_HHMMSSZ

Run the script directly:

./scripts/automatic-kvm-snapshots.sh

Example cron entry for hourly snapshots:

0 * * * * /path/to/kvm-tools/scripts/automatic-kvm-snapshots.sh

Example with a custom retention count:

0 2 * * * RETENTION=7 /path/to/kvm-tools/scripts/automatic-kvm-snapshots.sh

The test harness uses fake virsh and date commands, so it can run without libvirt installed:

bash tests/automatic-kvm-snapshots-test.sh

Static checks:

shellcheck scripts/automatic-kvm-snapshots.sh tests/automatic-kvm-snapshots-test.sh
bash -n scripts/automatic-kvm-snapshots.sh tests/automatic-kvm-snapshots-test.sh