This guide will show you how to create compressed, deduplicated, and encrypted backups of your server's home directory automatically using Borg, storing them on an offsite location.
You can adapt this guide for other Linux distributions with slight modifications. Borg is compatible with many operating systems.
On both the primary server and offsite server, install BorgBackup.
$ sudo apt install borgbackup
Before creating a backup, ensure you have sufficient disk space on both machines. Borg requires a few gigabytes of free space on the primary server in order to function.
$ df -h
Log into the offsite server and create a directory for Borg to use as a repository for the backups. Borg stores backups in a repository as a collection of archives.
$ mkdir /home/user/backup
On the primary server initialize a repository at the directory just created, where
username is the remote user with read/write access to the backup directory, and
offsite_server is the IP address of the remote server. When prompted, enter a strong passphrase to encrypt the repository.
$ borg init --encryption=repokey username@offsite_server:/home/user/backup [...] IMPORTANT: you will need both KEY AND PASSPHRASE to access this repo! Use "borg key export" to export the key, optionally in printable format. Write down the passphrase. Store both at safe place(s).
Borg saves a key in the repository in the
config file that needs to be present in order to access the repository. Export this key in case the file ever becomes corrupted or lost. Both the key and passphrase are needed to access the repository.
Create a directory to store the key on the primary server.
$ mkdir -p /home/user/.config/borg/keys
Export the key to this directory.
$ borg key export username@offsite_server:/home/user/backup /home/user/.config/borg/keys/backup_repo_key
To import the key if the file ever becomes damaged, change
BORG_PASSPHRASE environment variables to prevent reentering these details in this session.
$ export BORG_REPO='username@offsite_server:/home/user/backup' $ export BORG_PASSPHRASE='your repository passphrase'
Before creating a backup, configure Borg to connect to the offsite server without a password.
On the primary server, create a key pair for Borg.
$ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/your_home/.ssh/id_rsa):
Save the key as
/home/user/.ssh/id_rsa_borg and do not enter a passphrase.
Add the new public key to the offsite server.
$ ssh-copy-id -i '/home/user/.ssh/id_rsa_borg' username@offsite_server
Once complete, ensure you are able to log in to the offsite server without a passphrase using the new keyfile.
$ ssh -i '/home/user/.ssh/id_rsa_borg' username@offsite_server
To increase security, limit the keyfile to be used for Borg only and dissallow remote logins.
On the offsite server, edit the
$ sudo nano /home/user/.ssh/authorized_keys
Find the public key you added earlier. For example:
ssh-rsa AAAAB3Nza[...]q34Pk= email@example.com
Insert the command directive below before ssh-rsa to limit the key to the
borg command and a specific path only. Be sure to change
/home/user/backup to the path of the backup repository created earlier. The line will look like this:
command="borg serve --restrict-to-path /home/user/backup",restrict,no-pty,no-agent-forwarding,no-port-forwarding ssh-rsa AAAAB3Nza[...]q34Pk= firstname.lastname@example.org
Save and exit the file and return to the primary server.
Attempt to log in using the keyfile and verify access is denied.
$ ssh -i '/home/user/.ssh/id_rsa_borg' username@offsite_server PTY allocation request failed on channel 0
Press ENTER to receive the second message.
$LOG ERROR borg.archiver Remote: Borg 1.1.11: Got unexpected RPC data format from client. Connection to <IP> closed.
Once verified, export the
BORG_RSH environment variable to tell Borg to use this keyfile in this session.
$ export BORG_RSH='ssh -i /home/user/.ssh/id_rsa_borg'
On the primary server, test a backup of a file or folder in the home directory. Name it something appropriate and ensure you are not prompted for a passphrase.
$ borg create ::backup_name /home/user/path/to/file
To exclude a file or directory from a backup use
--exclude=path/to/file/. For example, if you want to exclude the
.cache directory when creating a backup, use:
$ borg create --exclude='/home/user/.cache' ::backup_name /home/user/path/to/file
Note: Include the full path when specifying what to exclude. For instance, use
.cache. Use multiple --exclude=path/to/file/ directives when excluding multiple files and directories. You may also use an exclude file if you have many exclusion patterns.
List the backups created in the repository using the
list command, ensuring the backup archive just created is there.
$ borg list backup_name Wed, 2020-09-22 12:59:37 [f2cd0350f6cde7d58bb429fe67fg7f11h35f5bd6cdaz1b6d4d5e7b304gjjf81f]
Test a restore of the backup using
borg extract. By default, Borg restores the full path of the backup to the current directory. For example in this guide, Borg restores the directories
/home/user/path/to/file. To avoid writing any data, include
--dry-run in the command.
$ borg extract --dry-run ::backup_name
To extract a single file in an archive, use: $ borg extract ::backup_name /file/to/restore
When finished, you may delete the test backup archive.
$ borg delete ::backup_name
To automate a backup of the home directory, create a backup script to be run daily via
cron on the primary server.
$ nano borg-backup.sh
Enter the following, changing details where necessary. This script makes a backup of the
/home directory, excluding extraneous files, using the
prune command to keep a backup for each day of the week, one for each week and one for each month, automatically deleting extra backups to save space.
#!/bin/sh # Backup home directory to a remote location using Borg. # To restore: borg extract username@offsite_server:/path/to/backup_repo::backup_name export BORG_RSH='ssh -i /home/user/.ssh/id_rsa_borg' export BORG_REPO='username@offsite_server:/home/user/backup' export BORG_PASSPHRASE='your repository passphrase' # Backup /home excluding cache & downloads borg create -v --stats ::$(hostname)-$(date +"%d-%b-%Y") /home \ --exclude '/home/*/.cache' \ --exclude '/home/*/.ccache' \ --exclude '/home/$USER/Downloads' \ # Prune extra backups borg prune --prefix $(hostname)- --keep-daily=7 --keep-weekly=4 --keep-monthly=12 exit 0
Save and exit the file.
Make the script executable.
$ chmod +x borg-backup.sh
Test the script to ensure the backup completes successfully.
Move the script to
/etc/cron.daily to be executed automatically each day.
$ mv borg-backup.sh /etc/cron.daily
You have now successfully set up secure, automated backups of your server's home directory to an offsite location with BorgBackup.