Introduction to BorgBackup
By Kannan Ponnusamy
September 10, 2020
What is Borg?
BorgBackup (Borg for short) is a ‘deduplicating’ backup program that eliminates duplicate or redundant information. It optionally supports compression and authenticated encryption.
The main objective of Borg is to provide an efficient and secure way to backup data. The deduplication technique utilized to produce the backup process is very quick and effective.
Step 1: Install the Borg backups
On Ubuntu/Debian:
apt install borgbackup
On RHEL/CentOS/Fedora:
dnf install borgbackup
Step 2: Initialize Local Borg repository
Firstly, the system that is going to be backed up needs a new designated backup directory. Name the parent directory ‘backup’ and then create a child directory called ‘borgdemo’, which serves as the repository.
mkdir -p /mnt/backup
borg init --encryption=repokey /mnt/backup/borgdemo
Step 3: Let’s create the first backup (archive)
In Borg terms, each backup instance will be called an archive. The following demonstrates how to backup the ‘photos’ directory and designate the archive as ‘archive_1’.
borg create --stats --progress /mnt/backup/borgdemo::archive_1 /home/kannan/photos
Note: the archive label for each backup run needs to be specified.
Step 4: Next backup (Incremental)
In order to see if the run was successful, the same command will be executed again. However, this time, with the different unique archive label.
borg create --stats --progress /mnt/backup/borgdemo::archive_2 /home/kannan/photos
The following backup is mostly identical to the previous one. Because of deduplication, the process will not only run faster this time, it will be incremental as well. The --stats flag will provide statistics regarding the size of deduplication.
Step 5: List all the archives
The ‘borg list’ command lists all of the archives stored within the Borg repository.
borg list /mnt/backup/borgdemo
Step 6: Remote Borg Repository
Take the scenario where the backups of many servers need to be maintained in a separate server. In this instance, a directory needs to be created for each of the systems that will be backed up. For this backup repository, create a folder named ‘backup’, and then within ‘backup’ a folder called ‘linode_01’. This folder will be initialized as a Borg repository.
mkdir -p /mnt/backup/linode_01
borg init --encryption=repokey user@backup_server:/mnt/backup/linode_01
The username, backup_server, repo can of course all be customized at the user’s discretion.
While initialising the repo, a passphrase for each backup repository can be set for authentication.
Step 7: Create an initial backup to the remote Borg repository
borg create --stats ssh://user@backup_server/mnt/backup/linode_01::archive_1 /home/kannan/photos
To enable the remote backups, the following three environment variables can be used to simplify the automation process:
export BORG_REPO='ssh://user@backup_server/mnt/backup/linode_01'
export BORG_PASSPHRASE='set_your_passpharase'
export BORG_RSH='ssh -i /home/kannan/.ssh/id_rsa_backups'
With those environment variables set, the ‘borg create’ command can be shortened to the following:
borg create --stats ::archive_1 /home/kannan/photos
Step 8: Excluding certain directories or files
In order to exclude certain directories or files, the create command has an --exclude option or an exclude file/directory pattern can be generated. For example, the following command demonstrates how to exclude /dev and /opt:
borg create --stats ::archive_1 / --exclude /dev /opt
Step 9: Restoring an archive through extraction
The ‘borg extract’ command extracts the contents of an archive. As a preset default, the entire archive will be extracted. However, the extraction can be limited by passing the directory path or file path as arguments to the command. For example, this is how a single photo can be extracted from the Photos archive:
borg extract ::archive_1 /home/kannan/photos/sunrise.jpg
Step 10: Pruning older backups
Every backup solution should have a way to maintain the older backups. Borg offers us borg prune for this. It prunes a repository by deleting all archives not matching any of the specified retention options.
For example, retain the final 10 archives from the day, another 6 end-of-week archives, and 3 of the end-of-month archive for every month using the following syntax:
borg prune -v --list --keep-daily=10 --keep-weekly=6 --keep-monthly=3 ::
Note that the double colons :: are required in order to automatically use the environment variables that were set prior.
For more in-depth documentation on Borg backup, read the docs.
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