Question: I'm trying to install OpenCV for use with [Pastec](http://www.pastec.io) on an Amazon Linux instance. This is my first time using an Amazon service, and I don't have much experience using linux...

How would I install OpenCV and it's dependencies on Amazon Linux?

I have tried adding the EPEL repository using this command:

```
$ sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

```

... which works but it still won't install OpenCV...

```
$ sudo yum --enablerepo=epel install opencv-core
Loaded plugins: priorities, update-motd, upgrade-helper
948 packages excluded due to repository priority protections
Nothing to do

```

Answer: 
It seems that default `yum` repo for **Amazon AMI** doesn't contain **OpenCV** packages.

You can compile it from sources by yourself with the following simple steps:

* install necessary packages:

`sudo yum install git cmake gcc-c++`

* clone **OpenCV** from repository:

`git clone https://github.com/Itseez/opencv.git`

* (optionally) choose required version:

`git checkout <required version>`

* compile and install - create folder in which you want to build it, enter there and type:

`cmake <path to sources>
 make
 sudo make install`

It's basic steps - after this you will have **OpenCV** with some default modules. You can read **cmake** output and adjust your installation before actual build. Possibly you should install additional packages for your needs (like *libpng*, *libjpg*, *python* etc.).
cmake should be higher than 3.5 in latest linux versions for the purpose of installing opencv and other packages. To install in Fedora or similar flavour use 
`sudo yum install cmake3`