Duplicity Charm

Overview

The Duplicity charm provides functionality for both manual and automatic backups for a deployed application. As the name suggests, it utilizes the Duplicity tool and acts as an easy-to-use-and-configure interface for operators to set up backups.

After relating the Duplicity charm to another charm, you can backup a directory to either the local unit, a remote host, or even an AWS S3 bucket. All it takes is a bit of configuration and remote destination preparation.

The following backends are currently supported:

• File (local)
• S3
• SCP
• Rsync
• FTP/SFTP

Usage

Simple deployment

This will get duplicity deployed on whatever deployed charm you want. Here, we see it being related to the ubuntu charm.

juju deploy ubuntu
juju deploy duplicity
juju add-relation duplicity ubuntu

However, we will need to fill out various other, required configs, depending on the backend type selected.

Local file backups

This will backup a selected directory to the local unit.

juju config duplicity \
    backend=file \
    remote_backup_url=file:///home/me/backups
    aux_backup_dir=/path/to/back/up

SCP/Rsync/SFTP Backups

Using the backends scp, rsync, and sftp require, at minimum, the following options to be set.

juju config duplicity \
    backend=scp \
    remote_backup_url=my.host:22/my_backups
    known_host_key='my.host,10.10.10.2 ssh-rsa AAABBBCCC' \
    private_ssh_key="$(base64 my_priv_id)"

Alternatively, you can use remote_password=password instead of the private_ssh_key option if you prefer password authentication.

S3 Backups

The following will backup to S3 buckets. This configuration requires an IAM account access and secret key to be passed into the config.

juju config duplicity \
    backend=s3 \
    remote_backup_url=s3:my.aws.com/bucket_name/prefix \
    aws_access_key_id=my_aws_key \
    aws_secret_access_key=my_aws_secret

Encryption

To encrypt your backups, you can use symmetric encryption using a passed in password or encrypt the backup with a GPG key. Alternative to these methods, you can ignore encryption entirely.

# Symmetric password encryption
juju config duplicity encryption_passphrase=my_passphrase

# Asymmetric GPG encryption
juju config duplicity gpg_public_key=MY_GPG_KEY

# Disable encryption (not recommended)
juju config duplicity disable_encryption=True

Setting Periodic Backups

The big draw of this charm is being able to periodically backup a directory. By default, the charm will only backup manually, i.e. through the do-backup action. To enable periodic backups, set backup_frequency to any of the following:

• hourly
• daily
• weekly
• monthly
• any valid cron schedule string

Setting Retention

The charm supports periodically cleaning up stale backups. A retention period can be set with retention_period and the charm will periodically delete backups older than this time period. By default, the charm's retention policy is set to manual and can be set as follows:

• manual (default)
• h (number of hour(s) eg. 3h, 60h, 10000h)
• d (number of day(s) eg. 1d, 7d, 30d, 100000d)

How frequently old backups are deleted can be set with deletion_frequency which by default is set to daily.

• daily (runs at 23:00) (default)
• hourly (runs at the 40th minute)
• any valid cron schedule string

Adding NRPE Checks for alerting

Adding NRPE checks allows for alerting when a periodic backup or deletion fails to complete.

juju deploy nrpe
juju add-relation nrpe ubuntu       # required on host
juju add-relation nrpe duplicity

Cleaning up backups

Deletion commands such as remove-older-than, remove-all-but-n-full and remove-all-inc-of-but-n-full can be used with run action and a specified parameter. For example: juju run-action duplicity/0 remove-older-than time=2022-10-02T19:44:00+00:00 where time follows the same w3 standard as duplicity and yaml juju run-action duplicity/0 remove-all-but-n-full count=1

Known Limitations and Future Features

This charm is currently still under development. The only supported Duplicity actions right now is full backups (through both an action and periodic backups) and removal of backups. The following is the list of future Duplicity functionality:

• incremental backups
• restoring backups
• verifying backups
• listing backed-up files
• additional supported backends

Upstream and Bugs

The repository can be found here.

Please report bugs or feature requests on Launchpad.