Attic is a secure backup program for Linux, FreeBSD and Mac OS X. Attic is designed for efficient data storage where only new or modified data is stored.


Space efficient storage
Variable block size deduplication is used to reduce the number of bytes stored by detecting redundant data. Each file is split into a number of variable length chunks and only chunks that have never been seen before are compressed and added to the repository.
Optional data encryption
All data can be protected using 256-bit AES encryption and data integrity and authenticity is verified using HMAC-SHA256.
Off-site backups
Attic can store data on any remote host accessible over SSH as long as Attic is installed.
Backups mountable as filesystems
Backup archives are mountable as userspace filesystems for easy backup verification and restores.


Deduplication is a technique for improving storage utilization by eliminating redundant data.
An archive is a collection of files along with metadata that include file permissions, directory structure and various file attributes. Since each archive in a repository must have a unique name a good naming convention is hostname-YYYY-MM-DD.
A repository is a filesystem directory storing data from zero or more archives. The data in a repository is both deduplicated and optionally encrypted making it both efficient and safe. Repositories are created using attic init and the contents can be listed using attic list.
Key file
When a repository is initialized a key file containing a password protected encryption key is created. It is vital to keep this file safe since the repository data is totally inaccessible without it.