Encrypted off-site backup of Proxmox VE vzdump images for $5/month/TB

This plugin to vzdump will hook into after a single VM backup is done. It will

split the .vma.lzo file that vzdump wrote to chunks of configurable size (default is 2 GB, B2 allows up to 5 GB=5*10^9 byte)
encrypt them using a symmetric key (password - no GPG keys used),
upload them to Backblaze B2 to a configurable path (default: hostname) under a configurable bucket,
delete the local copy of the backup and
remove all remote backups at B2 for the VM/LXC except the one it just uploaded.

Every step is checksummed and the checksum file is uploaded as well.

After all chunk uploads are finished, the local copy of the backup is deleted. Therefore you only need twice the size of the largest VM's backup file on the host. The backup is read and written multiple times, so using different storage devices for VMs and backup is a good idea.

Preparation

Get a Backblaze account and generate an application key along with a bucket.

Install git and download this repository:

apt-get install -y git
git clone https://github.com/TrueWinter/vzdump-plugin-b2.git /usr/local/bin/vzdump-plugin-b2

Alternatively transfer it manually to the server.

Install jq:
```
apt-get install -y jq
```
Make a copy of upload-b2.config.template and edit it to your parameters. If you put it anywhere else than the filename upload-b2.config in the same directory as vzdump-plugin-upload-b2.sh, also edit that script and make CONFIG_FILE point to it.
In that config file, note GPG_PASSPHRASE_FILE. That should point to a file containing your long, random and secret passphrase. You can use this do generate one:
```
test -r /root/vzdump-passphrase.txt || dd if=/dev/random bs=1 count=48 2>/dev/null | hexdump -v -e '"%02X"' > /root/vzdump-passphrase.txt
```
Remember and save that string - your backups are unusable without it!

Make vzdump aware of the script by adding a line to /etc/vzdump.conf:

echo "script: /usr/local/bin/vzdump-plugin-b2/vzdump-plugin-upload-b2.sh" >> /etc/vzdump.conf

Download the b2 command-line utility as documented here:

wget -O /usr/local/bin/b2 https://github.com/Backblaze/B2_Command_Line_Tool/releases/latest/download/b2-linux
chmod +x /usr/local/bin/b2

Note that container backups are only a few hundred MB, while VM backups are at least 2.5GB (at least for Ubuntu). For this reason, it is recommended that you use containers wherever possible.

Testing

A manual backup of a small VM is a good idea to test general functionality. Look at the log output for hints what may have gone wrong.

Restoring backups

To restore backups, run the vzdump-b2-verify.sh script. You will need to pass three parameters:

The directory inside the bucket, e.g. hostname/rpool/backup/dump
The name of the (compressed) backup file, e.g. 'vzdump-qemu-100-2016_02_11-12_15_02'
A directory where the script can work. This directory must be empty

This script will download the files from Backblaze B2, decrypt them, verify the checksums, and join the split files together.