Snapm

Snapshot manager (snapm) manages named snapshot sets on Linux systems. Each snapshot set captures coordinated snapshots across multiple volumes, representing a consistent point-in-time system state that can be referenced and managed as a single unit.

Features

• Coordinated snapshot sets: Create coordinated snapshots across multiple volumes
• Bootable snapshots: Generate boot entries for snapshot boot and failsafe revert
• Multiple backends: Support for LVM2 (Copy-on-Write and Thin) and Stratis
• Flexible scheduling: Integration with systemd timers for automated snapshot creation with retention policies
• Size policies: Flexible snapshot sizing with multiple strategies
• Difference engine: Compare snapshot sets to identify added, removed, moved, and modified files with multiple output formats
• Plugin architecture: Extensible design for additional storage backends

Screenshots

Difference Engine Tree Output

Compare a snapshot set to the running system with a hierarchical tree view:

Difference Report

Generate tabular reports of changes between snapshot sets:

Quick Start

Installation

From RPM (Fedora/CentOS/RHEL)

Install from distribution repositories (when available):

dnf install snapm boom-boot

Manual Installation

1. Create and activate a virtual environment:

python3 -m venv --system-site-packages .venv && source .venv/bin/activate

2. If boom-boot is not installed from your distribution's packages, clone and install it with pip:

git clone https://github.com/snapshotmanager/boom-boot.git
cd boom-boot
python3 -m pip install .

3. Repeat the process with the snapm repository:

git clone https://github.com/snapshotmanager/snapm.git
cd snapm
python3 -m pip install .

Basic Usage

Create a bootable snapshot set

Create a snapshot set named "before-upgrade" of root and home, with snapshot boot and revert boot entries:

snapm snapset create --bootable --revert before-upgrade / /home

List snapshot sets

snapm snapset list

Show detailed information:

snapm snapset show before-upgrade

Boot into a snapshot

• Reboot and select the snapshot boot entry from the GRUB menu
• Entry will be named: "Snapshot before-upgrade YYYY-MM-DD HH:MM:SS (version)"
• Optionally run grub2-reboot <title> to pre-select snapshot boot entry, e.g.:

grub2-reboot "Snapshot before-upgrade YYYY-MM-DD HH:MM:SS (version)"

• Use grub-reboot instead of grub2-reboot on Debian and Ubuntu systems.

Revert to snapshot state

snapm snapset revert before-upgrade

Then reboot into the Revert boot entry.

Note: Reverting destroys the snapshot set (snapshots are merged back into the origin volumes).

Clean up

Delete snapshot set when no longer needed:

snapm snapset delete before-upgrade

Common Workflows

System Updates

Before major system updates:

snapm snapset create --bootable --revert pre-update / /var

If update goes wrong, revert:

snapm snapset revert pre-update

When satisfied with update, clean up:

snapm snapset delete pre-update

Development Snapshots

Quick development checkpoint:

snapm snapset create dev-checkpoint /home /var

Continue working...

If needed, revert specific volumes by splitting them into a dedicated snapshot set first:

snapm snapset split dev-checkpoint dev-checkpoint-home /home

Example output:

SnapsetName:      dev-checkpoint-home
Sources:          /home
NrSnapshots:      1
Time:             2025-08-30 12:44:00
UUID:             ee82269f-8c78-5814-b47a-b9be31bcebb5
Status:           Inactive
Autoactivate:     no
Bootable:         no

snapm snapset revert dev-checkpoint-home

Alternatively revert the entire snapshot set:

snapm snapset revert dev-checkpoint

Understanding Changes

Compare a snapshot set to the current system to see what changed:

snapm snapset diff pre-update .

View changes as a hierarchical tree (default):

snapm snapset diff --output-format tree pre-update .

Generate a unified diff of modified file contents:

snapm snapset diff --output-format diff pre-update .

Get a summary of change counts:

snapm snapset diff --output-format summary pre-update .

Export changed paths for use with other tools:

snapm snapset diff --output-format paths pre-update . | xargs tar cvf changes.tar

Generate a tabular report of differences:

snapm snapset diffreport -o path,type,size_delta pre-update .

Documentation

• User Guide - Comprehensive usage documentation
• API Documentation - Auto-generated API docs
• Manual Pages - System manual pages

Requirements

• Linux system with LVM2 or Stratis volumes
• boom-boot
• Root privileges for performing storage operations
• Python 3.9+

Supported Storage Backends

Backend	Type	Snapshots	Thin Provisioning	Status
LVM2	Copy-on-Write	✓	✗	Stable
LVM2 Thin	Thin Pools	✓	✓	Stable
Stratis	Thin Pools	✓	✓	Stable

Contributing

We welcome contributions! Please see CONTRIBUTING.md for guidelines.

Support

• GitHub Issue Tracker
• User Guide
• API Docs

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

The Snapshot Manager logo incorporates an image of Tux, the Linux mascot originally conceived and designed by Larry Ewing.

Related Projects

• boom - Boot manager for Linux snapshot boot
• stratis-cli - Command-line tool for Stratis storage
• lvm2 - The LVM2 logical volume manager