Zaloha.sh

Zaloha is a small and simple directory synchronizer:

Zaloha is a BASH script that uses only FIND, SORT and AWK.
All you need is the Zaloha.sh file (contains ~76 kB of program code and ~78 kB of documentation).
No compilation, installation and configuration is required.
Cyber-secure: No new binary code, no new open ports, easily reviewable.
Both directories must be available locally (local HDD/SSD, flash drive, mounted Samba or NFS volume).
Zaloha does not lock files while copying them. No writing on either directory may occur while Zaloha runs.
Zaloha always copies whole files via the operating system's CP command (= no delta-transfer like in RSYNC).
Zaloha is not limited by memory (metadata is processed as CSV files, no limits for huge directory trees).
Zaloha has optional reverse-synchronization features.
Zaloha can optionally compare files byte by byte.
Zaloha prepares scripts for case of eventual restore.

Full documentation is available both online as well as inside of Zaloha.sh.

On Linux/Unics, Zaloha runs natively. On Windows, Cygwin is needed.

What are synchronization programs good for ?

Read article here.

How does Zaloha.sh work ?

Explained in five sentences

FIND is executed to scan both directories to obtain CSV metadata about files and subdirectories.
The CSV metadata is compared by a sequence of sorts and AWK processing steps.
The results (= prepared synchronization actions) are presented to the user for confirmation.
If the user confirms, the synchronization actions are executed.
A non-interactive regime is available as well.

Explained by an Interactive Flowchart

Open Interactive JavaScript Flowchart here.

Explained in full detail

Read the relevant sections in the Documentation.

Obtain Zaloha.sh

The simplest way: Under the green button "Code" above, choose "Download ZIP". From the downloaded ZIP archive, extract Zaloha.sh and make it executable (chmod u+x Zaloha.sh).

For running the Simple Demo, extract also the scripts Simple_Demo_step1/2/3/4/5/6/7.sh and make them executable.

Usage Example

Zaloha.sh --sourceDir="test_source" --backupDir="test_backup" [other options, see docu]

Usage Screenshot

Performance data

Performance was measured on following system and data:

Standard commodity PC with Intel i3, 3.3GHz, 4GB RAM
Source directory: local Seagate HDD 500GB, 7200rpm, SATA III
Backup directory: a second local Seagate HDD 500GB, 7200rpm, SATA III
Filesystem: ext4 on both HDDs
Data synchronized: 110 GB, 88.000 files
Operating system: Linux (Fedora 30)
Binary utilities used by Zaloha: GNU find, GNU sort, mawk
Zaloha options: --noRestore YES, --mawk YES, --hLinks NO, --byteByByte NO

Measured performance of the analysis phase:

first run: 25 seconds (filesystem data not cached in the OS: the FINDs 2 x 12 secs, the sorts and AWKs 1 sec)
second run: 5 seconds (filesystem data cached in the OS: the FINDs 2 x 2 secs, the sorts and AWKs 1 sec)

Performance of the execution phase:

depends on how many files need synchronization: zero to several minutes

Development status

From the perspective of my own requirements and ideas, Zaloha is a completed work.
Zaloha successfully passes all my test cases.
Eventual (conclusive) Problem Reports are welcome (via Issues).
Enhancement Requests so far they won't contradict the "small and simple synchronizer" idea (= no program code inflation, no new processing steps, no increase in runtime etc).

Add-on script Zaloha_Snapshot.sh

An add-on script to create hardlink-based snapshots of the backup directory exists: Zaloha_Snapshot. This allows to create Time Machine-like backup solutions.

License

MIT License

Norcoen/Zaloha.sh