Packrat

Packrat is an automated, modular backup system written in Bash. It has the ability to do encrypted, incremental backups of your filesystem and can store them somewhere offsite via FTP, SSH, or S3.

It can also backup MySQL and PostgreSQL databases, though these will not be incremental backups, always a full dump.

Packrat has no ability to perform a restore process. You'll have to do this yourself. See the Filesystem Restores section for a quick tutorial on how to perform a restore with the dar utility.

Before trusting a backup system, a conscientious operator should always test it by performing a restore. Don't wait until you need it!

Installation

• Copy packrat.conf to /etc/packrat.conf
• Copy the modules directory /usr/share/packrat/modules
• Copy the packrat and aws scripts to somewhere in your PATH (eg: /usr/bin)
  • The aws script is only required if you're using the S3 upload module.
• Install the dar utility. It's probably included your distro's package set somewhere.

Setup

All global- and module-level configuration is done in packrat.conf. Since this file will likely contain encryption keys or other sensitive data, you should probably make it readable only by root (chmod 600 /etc/packrat.conf).

The configuration file is heavily-commented and should be reasonably self-explanatory.

Filesystem Backups

Though Packrat is modular, its main focus is backing up parts of your filesystem. This functionality is contained in the filesystem module, and it is the first section in the packrat.conf configuration file.

Packrat uses the dar utility to perform file-based backup and restore. It supports slicing, encryption, and incremental backups, so it's well-suited to the task.

Provided the configuration variables are set correctly, Packrat should handle the backups for you just fine.

But it doesn't do restores. That's your job.

Filesystem Restores

Since dar is an incremental backup utility, you will need multiple backup files to get back to your last backup point.

For example, let's say it's 2016-02-16, and you experience a catastrophic loss of data. A hard drive gained sentience and decided that it couldn't live without new episodes of Seinfeld, so it self-terminated. These things happen.

You go into your backups directory to restore your /home/sites directory, and you see these files:

myserver-home-sites-20160211.1.dar
myserver-home-sites-20160212.1.dar
myserver-home-sites-20160213.1.dar
myserver-home-sites-20160214.master.1.dar
myserver-home-sites-20160214.master.2.dar
myserver-home-sites-20160215.1.dar
myserver-home-sites-20160216.1.dar

Good, we have backups right up to the current day. The files with a master string in them are exactly that, masters -- these are full backups, containing every file as it existed on that date. You'll note that there are two master files for 2016-02-14. That's because we're using slices in order to cap the maximum file size of any one backup file. The .2.dar file continues the archive where the .1.dar file left off.

The other files, the ones with dates following the last master, are the incrementals. These archives only store the files that have changed since the last master was taken.

Because of this, we need the master files in order to restore. An incremental file is not enough.

Let's also assume we used encryption on our backup files, and that we want to restore the content of this archive to a different directory so we can verify the contents before moving them into their original location.

To accomplish this, we'll have to restore each file from the most recent master archive onwards, and in the order they were taken. We'll also omit the slice and extension from the filenames, as dar will attach that part itself.

# dar -x myserver-home-sites-20160214.master -R /restore_test -K costanza
# dar -x myserver-home-sites-20160215 -R /restore_test -K costanza
# dar -x myserver-home-sites-20160216 -R /restore_test -K costanza

At this point, we should should have our files fully restored in the /restore_test directory. Huzzah!

For more nitty-gritty details, check out the dar tutorial.

Creating New Modules

At present, Packrat only has a handful of included modules. If you need some new functionality, then it's likely that you'll have to write your own. You can use some of the modules in the modules/ subdirectory for your inspiration.

There are two types of modules: backup modules and upload modules.

Backup Modules

A backup module understands how to backup a given resource (eg: a filesystem, a database, a Redis store, etc).

Backup modules need to implement a single function called mod_<name>, where <name> is the name of the module. The function does not receive any arguments.

Upload Modules

An upload module understands how to store this backup archive somewhere, and how to remove old, outdated archives.

Upload modules need to implement three functions:

• mod_<name>: Uploads new archives to the remote. Accepts no arguments.
• list_<name>: Generates a list of files on the remote. Accepts no arguments.
• purge_<name>: Deletes a file from the remote. Accepts one argument, the filename to remove.

Tips

• If using the same remote location (FTP, S3, whatever) for backing up multiple servers, you should use a different directory/bucket for each server. Otherwise some upload modules can get confused when they're counting file archives to determine how many old ones to remove.