apt-get install duplicity
Download Duply. Extract and copy duply into /usr/bin. Make sure it has execute permissions for the user you plan to run your backups with (e.g. root).
Make a directory for the configuration files.
mkdir /etc/duply
Create a new profile.
duply offsite create
Make sure Duply created a conf file in /etc/duply/offsite.
Create a GPG key.
gpg --gen-key
While logged in via SSH, key generation could fail (Not enough random bytes available). To remedy this, open another shell and install rngtools:
apt-get install rng-tools
And run:
rngd -r /dev/urandom
If successful, you should see an output like the following:
gpg: /root/.gnupg/trustdb.gpg: trustdb created
gpg: key 525D8AF3 marked as ultimately trusted
public and secret key created and signed.
Make a note of the key number (here: 525D8AF3).
Make sure the key was added to the keystore:
gpg --list-keys
Edit the config file:
vim /etc/duply/offsite/conf
Fill in the GPG key number and the passphrase.
Set up cronjob:
27 4 1 * * root /usr/bin/duply offsite backup_verify_purge --force
23 3 * * * root /usr/bin/duply offsite backup
This guide was largely lifted from a tutorial found on trick77.com and a couple of other places.