bart

bart - backup and restore tool

Overview

bart is a simple backup/restore tool for data stored in a local file system. Currently bart only supports backing up to Azure Storage blobs or to a file system.

bart supports the following:

• backup of local files
• restore of files missing locally but available in the archive
• password based AES encryption for the archive index and archived files
• concealing original file paths in backup archives by hashing them

Disclaimer: Use at your own risk!

Usage

bart has a few sub-commands:

• backup to run in backup mode, in which bart looks for files that are present locally, but not in the backup archive.
• restore to run in restore mode, where bart goes through all files found in the backup archive and checks if they're present locally too.
• cleanup to remove files in the backup archive or locally depending on the -l (location) flag.

Each of the sub-commands supports the -whatif flag. When the flag is specified, bart lists (on stdout) the files that would be affected, but does not actually back them up, restore them, or clean them up. Thus, the -whatif flag can be used to determine what would be done if it was done for real.

You can get more information on the flags available for each sub-command by running

bart <sub-command> --help

After parsing command line arguments and making sure everything is in order, bart will ask you for a password. This password is used together with a salt (randomly generated the first time a backup archive in a target store is touched) to derive a symmetric encryption key. This key is used to encrypt each file before it is uploaded in backup mode to the target store, or to decrypt each file before it is downloaded in restore mode from the target store.

The password can either be entered by the user after the program has started, or it can be piped into bart as follows. Any other means to pipe the password works too, of course.

$ cat .password
my-password
$ cat .password | bart <sub-command>

Target Azure Storage blobs

To use a backup archive stored in Azure Storage blobs, you must provide bart with two pieces of information:

1. The blob service endpoint URL for an Azure Storage account, through the -azep flag on the command line. The value typically looks like https://your-storage-account-name.blob.core.windows.net/ where your-storage-account-name is the name of the storage account you want to use in Azure. The blob service endpoint URL can be found in the Azure portal under Endpoints for the storage account in question. The DNS suffix may look different depending on the cloud (Public vs Government vs China etc.) you're using.

2. A credential to access the Azure Storage account. There are not command line switches to provide the credential, instead they must be passed in a way supported by the Azure Identity Client module. The module will try to look for a credential using the following order:

   1. Environment variables
   2. Azure Workload identity
   3. Managed identities
   4. Azure CLI credential

   When running bart in an Azure workload itself, #2 and #3 above are best/easiest to use. When running in a shell where you're already logged in to Azure CLI, #4 is probably best. Otherwise, using the environment variables, typically in combination with a service principal may be easiest.

Target the file system

To use a backup archive stored in the file system itself, you must provide bart with one additional piece of information:

1. The root directory where the backup files should be added, through the -t (target) flag on the command line.

Build

To build bart by yourself you can take advantage of the makefile in the repo.

# build for your default OS and architecture for Azurite (Azure Storage emulator) target
make bart

# or, to build for Azure backup target
make bart TAGS=azure

# or, to also create the x86 and x64 binaries for Windows
make all

Alternatively, you can just use go build -tags <TAGS> yourself. The go build tags used are described in the table below.