Install Redis on old distributions

GitLab requires at least Redis 2.8. The following guide is for Debian 7 and Ubuntu 12.04. If you are using Debian 8 or Ubuntu 14.04 and up, follow the installation guide.

Install Redis 2.8 in Debian 7

Redis 2.8 is included in the Debian Wheezy backports repository.

Edit /etc/apt/sources.list and add the following line:

deb http://http.debian.net/debian wheezy-backports main

Update the repositories:
```
sudo apt-get update
```

Install redis-server:

sudo apt-get -t wheezy-backports install redis-server

Follow the rest of the installation guide.

Install Redis 2.8 in Ubuntu 12.04

We will use a PPA to install a recent version of Redis.

Install the PPA repository:
```
sudo add-apt-repository ppa:chris-lea/redis-server
```
Your system will now fetch the PPA's key. This enables your Ubuntu system to verify that the packages in the PPA have not been interfered with since they were built.
Update the repositories:
```
sudo apt-get update
```
Install redis-server:
```
sudo apt-get install redis-server
```
Follow the rest of the installation guide.