Monday, August 25, 2014

Backing up using git

Over the years I've found that as I move from machine to machine, whether adding a new machine to my collection or replacing an old one, it's a pain to constantly copy files from one place to the next. I've also found that the backup process tends to be error prone as I either forget to back something up, don't backup often enough because of having to plug in the extra drive, needing to retrieve something that I've deleted, or I accidentally overwrite something in the backup.

There have been several projects, both open source and commercial, that help solve these problems by doing incremental backup. But I've found that they tend to be platform specific or not supported on the wide variety of machines I have in my mix. Most of them also still require you to use an external drive in order to protect against harddrive failure.

A few years ago I switched to using git as my backup mechanism. It doesn't require me to hassle with an external drive while still solving the problem of protecting against disk failure. It's supported on all major platforms. There are cloud hosting options as well as options to host locally. It provides incremental backup. I can easily exclude things from backup as well as retrieve deleted items.

Initial creation (one-time steps)

Create repository to back up to on backup machine

$ ssh your.backup.machine
$ mkdir -p /path/to/backup/location/my_backup_repository.git
$ cd /path/to/backup/location/my_backup_repository.git
$ git --bare init
$ exit

Add repository location on machine to backup

$ cd /path/to/backup
$ git init
$ git remote add origin USER@your.backup.machine:/path/to/backup/location/my_backup_repository.git
$ echo "backup using git" > README
$ git add README
$ git commit -m "Initial Commit"
$ git push origin master

Performing the backup

It's important that BEFORE you back anything up, you encrypt anything that you don't want backed up in the clear. I like to encrypt things using openssl because of it's wide range of platform availability.

Make sure that you .gitignore anything you don't want backed up. Often I backup my OS X ~/Documents folder. But this is the default location for some application configuration that I don't want backed up. It's important that you add these folders to your .gitignore so you don't unnecessarily back them up and use up unwanted space.

On backup machine

$ cd /path/to/backup
$ # encrypt any files you want encrypted
$ git status
$ git add .
$ git commit -m "backup $(date +'%Y-%m-%d_%H%M')"
$ git push

You now have a secondary backup of your important files. But even better you have a simple way to restore from a backup.

Restoring a backup

$ cd /path/to/restore/to
$ git clone USER@your.backup.machine:/path/to/backup/location/my_backup_repository.git ./


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