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Secure, Free, Incremental and Instant Backups for Linux

Written 6 years ago by Mike Cardwell

I use two different methods to backup the data on my laptop. The code that I am working on at any one time is backed up off-site as soon as it changes. Additionally, it sits under revision control. Along side this, my entire filesystem is incrementally backed up to network attached storage, on an hourly basis. Both solutions utilise encryption such that only I am able to recover data from those backups. Here follows a description of the technology and services that I use to achieve this.

Full System Backups

I like to backup the entire filesystem on my laptop. You might think that backing up folders like /sbin/ is a waste of time, but I prefer to err on the side of caution and keep everything. My backups are stored on a NAS which I mount on my laptop using CIFS. You can use the same method to backup to a USB attached hard drive, or to a machine with SSH/FTP access, or even to Amazon S3. To achieve this, I use some free software called Duplicity

I use full disk encryption on my laptop, so it would be silly to not use it for the backups as well. Duplicity will tar up your files, and then utilises GnuPGs symmetric option to encrypt the tarball with a passphrase. Only files which have been changed between the current time, and the previous backup, are backed up.

I make sure that NAS is automatically mounted on my laptop, and add the following to my crontab.

PASSPHRASE="theEncryptionPassphrase"
30 * * * * duplicity incr --full-if-older-than 4W --exclude-other-filesystems / file://backupdir
29 * * * * duplicity --force cleanup file://backupdir
28 * * * * duplicity --force remove-all-but-n-full 2 file://backupdir

If there is an environment variable named PASSPHRASE, then duplicity will use it for the encryption. In this example configuration, the first job runs an incremental backup once an hour. Every 4 weeks a new full system backup is performed. The second and third jobs clean up the backup directory. At any one time, I keep a minimum of two full system backups and their increments. The –exclude-other-filesystems option allows me to avoid other filesystems like /proc/ and /dev/ and the backup mount it’s self. You may want to create additional jobs for other partitions like /home/ depending on your partition scheme.

Say I wanted to restore a copy of /home/foo, exactly as it looked 10 days ago, I’d run a command similar to this:

duplicity -t 10D --file-to-restore home/foo file://backupdir /home/foo.restored

Instant Code Backups

I value the code that I write, more highly than the rest of the data on my laptop. I use Git for revision control, Dropbox for automatic synchronization of code off-site (to Amazon S3), and EncFS for encrypting the code before it leaves my system.

All of my development is done in project specific directories beneath /home/mike/git/. /home/mike/git/ is mounted from /home/mike/Dropbox/git.encfs/ using the encfs command:

encfs /home/mike/Dropbox/git.encfs /home/mike/git

Now, whenever I save anything in /home/mike/git/ an encrypted version in /home/mike/Dropbox/git.encfs is created/updated, and that change is immediately synced to the cloud. If Dropbox is compromised, I don’t have to worry about my code being compromised as it is encrypted.

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