#+TITLE: rsyncshot
#+AUTHOR: Craig Jennings

* About

rsyncshot creates space-efficient backups using rsync and hard links. Each snapshot looks like a full backup, but unchanged files share disk space across all snapshots.

Supports backing up to local drives (USB, NFS) or remote servers via SSH.

Inspired by [[http://www.mikerubel.org/computers/rsync_snapshots/][Mike Rubel's rsync snapshots]].

* Quick Start

#+begin_src sh
# Download and install
wget https://raw.githubusercontent.com/cjennings/rsyncshot/main/rsyncshot
sudo bash ./rsyncshot setup

# Or clone and install
git clone https://github.com/cjennings/rsyncshot
cd rsyncshot
make deps          # Install dependencies (auto-detects package manager)
sudo make install
#+end_src

After setup, edit =/etc/rsyncshot/config= to set your backup destination.

* Commands

| Command                    | Description                              |
|----------------------------+------------------------------------------|
| =rsyncshot backup=         | Run an immediate one-off backup          |
| =rsyncshot <name> <count>= | Create snapshot with name and retention  |
| =rsyncshot setup=          | Install script and configure cron jobs   |
| =rsyncshot status=         | Show installation and environment status |
| =rsyncshot list=           | Show existing snapshots with sizes       |
| =rsyncshot dryrun <n> <c>= | Preview backup without making changes    |
| =rsyncshot help=           | Show help message                        |

** Examples

#+begin_src sh
# Immediate backup (creates manual.0)
sudo rsyncshot backup

# Keep 24 hourly snapshots
sudo rsyncshot hourly 24

# Keep 7 daily snapshots
sudo rsyncshot daily 7

# Preview what would be backed up
sudo rsyncshot dryrun manual 1

# Check if everything is configured correctly
sudo rsyncshot status

# See existing snapshots
sudo rsyncshot list
#+end_src

* Configuration

All settings live in =/etc/rsyncshot/config=. Created automatically by =rsyncshot setup=.

** Backup Modes

*** Remote Mode (SSH)

Back up to a remote server over SSH:

#+begin_src sh
REMOTE_HOST="myserver"
REMOTE_PATH="/mnt/backups"
#+end_src

Backups go to =myserver:/mnt/backups/hostname/=.

If your SSH key isn't in root's =~/.ssh/=, specify the path:

#+begin_src sh
SSH_IDENTITY_FILE="/home/youruser/.ssh/id_ed25519"
#+end_src

*** Local Mode

Back up to a mounted drive (USB, NFS, etc.):

#+begin_src sh
REMOTE_HOST=""
MOUNTDIR="/media/backup"
#+end_src

Backups go to =/media/backup/hostname/=. If the drive isn't mounted, rsyncshot will try to mount it.

** What Gets Backed Up

Edit =/etc/rsyncshot/include.txt= - one directory per line (supports paths with spaces):

#+begin_src
/home
/etc
/usr/local/bin
# Comments start with #
#+end_src

** What Gets Excluded

Edit =/etc/rsyncshot/exclude.txt= - one pattern per line:

#+begin_src
# Caches and temp files
.cache
*.tmp
*.log

# Build artifacts
node_modules
__pycache__
*.pyc
#+end_src

** Lock File

rsyncshot takes an exclusive lock before each backup, so concurrent runs can't overlap (a slow backup overrunning the next cron tick fails fast instead of stacking up). Cron entries need no =flock= wrapper.

The lock defaults to =/run/lock/rsyncshot.lock= (a root-only directory), falling back to =/var/lock= then =/tmp=. Override it in the config if needed:

#+begin_src sh
LOCKFILE="/run/lock/rsyncshot.lock"
#+end_src

* Automatic Backups

Setup installs a default cron schedule:

| Type   | Schedule                    | Retention |
|--------+-----------------------------+-----------|
| Hourly | Every hour, 1am-11pm        | 22        |
| Daily  | Noon, Monday-Saturday       | 6         |
| Weekly | Noon, Sunday                | 51        |

The installed cron lines carry no =flock= wrapper - rsyncshot locks itself (see Lock File above).

Edit with =sudo crontab -e=.

* How It Works

1. rsync copies your directories to =destination/latest/=
2. Oldest snapshot beyond retention count is deleted
3. Existing snapshots rotate (=hourly.0= → =hourly.1= → =hourly.2=...)
4. =latest/= is hard-linked to =hourly.0= (or whatever type you specified)

Hard links mean unchanged files share disk space. A 100GB backup with 24 hourly snapshots might only use 110GB total if most files don't change.

Each source is stored under its full path (=/usr/local/bin= lands at =latest/usr/local/bin=), so sources never collide and restores are unambiguous. Ownership is preserved as numeric uid/gid, so a restore stays correct even when the destination has a different user/group database.

* Safeguards

- *Separate by hostname* - one drive can back up multiple machines
- *Internal lock* - prevents overlapping runs; no =flock= wrapper needed in cron
- *Validates sources* - checks directories exist before starting
- *Validates destination* - checks mount or SSH connectivity
- *Checks rsync exit code* - won't rotate if backup failed
- *Read-only snapshots* - prevents accidental deletion
- *Timestamped logging* - all runs logged to =/var/log/rsyncshot.log=

* Requirements

- bash
- rsync
- cron
- grep
- flock
- ssh (for remote mode)

The script checks for rsync and ssh at startup and shows install instructions if missing.

* Uninstalling

#+begin_src sh
# If you cloned the repo
sudo make uninstall

# Or manually
sudo rm /usr/local/bin/rsyncshot
sudo rm -rf /etc/rsyncshot
sudo rm /var/log/rsyncshot.log  # optional
sudo crontab -e  # remove rsyncshot entries
#+end_src

* Development

Run =make= to see all available targets:

| Target        | Description                                 |
|---------------+---------------------------------------------|
| help          | Show all targets (default)                  |
| install       | Install rsyncshot and configure cron        |
| uninstall     | Remove rsyncshot and config                 |
| deps          | Install dependencies (auto-detects distro)  |
| lint          | Run shellcheck static analysis              |
| check         | Run lint + full test suite                  |
| test          | Run full test suite                         |
| test-quick    | Run quick tests (skip backup/cron)          |
| test-verbose  | Run tests with verbose output               |

** Testing

An automated test suite is included in the =tests/= directory.

*** Running Tests

#+begin_src sh
# Run all tests (requires sudo)
sudo ./tests/test_rsyncshot.sh

# Skip slow backup/cron tests
sudo ./tests/test_rsyncshot.sh --quick

# Verbose output
sudo ./tests/test_rsyncshot.sh -v
#+end_src

*** Test Coverage

| Category    | Tests | Description                                                       |
|-------------+-------+------------------------------------------------------------------|
| Validation  |     9 | Input validation, help, arg checks, empty-path and zero-count guards |
| Functions   |     6 | is_mounted exact-match logic, derive_paths mode/path derivation   |
| Include     |     5 | Path parsing, comments, empty lines, spaces in paths             |
| Dry-run     |     4 | Preview mode doesn't modify anything                            |
| Rsync flags |     1 | rsync invoked with --numeric-ids and -R (relative paths)        |
| Backup      |     8 | Creation, copying, rotation, retention, exclusions, basename collisions |
| Cron        |     4 | Cron management, no duplicates, preserves jobs, no flock wrapper |
| Locking     |     3 | Refuses concurrent runs, dryrun not blocked, sequential runs     |
| Remote      | gated | Backup + rotation over SSH-to-localhost (skipped if unavailable) |
| Total       |    40 | (plus the gated remote suite when localhost SSH is available)    |

*** Test Structure

- =tests/test_rsyncshot.sh= - Main test runner
- =tests/lib/test_helpers.sh= - Assertion functions and test environment setup
- =tests/cases/test_validation.sh= - Input validation tests
- =tests/cases/test_functions.sh= - Unit tests for is_mounted and derive_paths
- =tests/cases/test_includes.sh= - Include file parsing tests
- =tests/cases/test_dryrun.sh= - Dry-run mode tests
- =tests/cases/test_rsync_flags.sh= - rsync invocation flag tests (command-capture shim)
- =tests/cases/test_backup.sh= - Backup and rotation tests
- =tests/cases/test_cron.sh= - Cron job management tests
- =tests/cases/test_locking.sh= - Concurrency lock tests
- =tests/cases/test_remote.sh= - Remote-mode (SSH) tests, gated on localhost SSH

* License

BSD 3-Clause. See [[file:LICENSE][LICENSE]] file.