Updated DOCKER.md to include info on checking versions for docker and docker-compose. People are getting tripped up by installs that aren't up to date

Author: mtesauro

DOCKER.md

@@ -9,6 +9,8 @@ use the [Helm and Kubernetes](KUBERNETES.md) approach.
 If you start your DefectDojo instance on Docker Compose for the first time, just
 run `docker-compose up`.
 
+**NOTE:** Installing with docker-compose requires the latest version of docker and docker-compose - at least docker 18.09.4 and docker-compose 1.24.0. See "Checking Docker versions" below for version errors during running docker-compose up.
+
 Navigate to <http://localhost:8080> where you can log in with username admin.
 To find out the admin user’s password, check the very beginning of the console
 output of the initializer container, typically name 'django-defectdojo_initializer_1', or run the following:
@@ -57,3 +59,82 @@ Removes all containers, networks and the database volume
 ```zsh
 docker-compose down --volumes
 ```
+
+## Checking Docker versions
+
+Run the following to determine the versions for docker and docker-compose:
+
+```zsh
+$ docker version
+Client:
+ Version:      17.09.0-ce
+ API version:  1.32
+ Go version:   go1.8.3
+ Git commit:   afdb6d4
+ Built:        Tue Sep 26 22:42:45 2017
+ OS/Arch:      linux/amd64
+
+Server:
+ Version:      17.09.0-ce
+ API version:  1.32 (minimum version 1.12)
+ Go version:   go1.8.3
+ Git commit:   afdb6d4
+ Built:        Tue Sep 26 22:41:24 2017
+ OS/Arch:      linux/amd64
+ Experimental: false
+
+$ docker-compose version
+docker-compose version 1.18.0, build 8dd22a9
+docker-py version: 2.6.1
+CPython version: 2.7.13
+OpenSSL version: OpenSSL 1.0.1t  3 May 2016
+```
+
+In this case, both docker (version 17.09.0-ce) and docker-compose (1.18.0) need to be updated.
+
+Follow [Dockers' documentation](https://docs.docker.com/install/) for your OS to get the lastest version of Docker. For the docker command, most OSes have a built-in update mechanism like "apt upgrade".
+
+Docker Compose isn't packaged like Docker and you'll need to manually update an existing install if using Linux. For Linux, either follow the instructions in the [Docker Compose documentation](https://docs.docker.com/compose/install/) or use the shell script below. The script below will update docker-compose to the latest version automatically. You will need to make the script executable and have sudo privileges to upgrade docker-compose:
+
+```zsh
+#!/bin/bash
+
+# Set location of docker-compose binary - shouldn't need to modify this
+DESTINATION=/usr/local/bin/docker-compose
+
+# Get latest docker-compose version
+VERSION=$(curl --silent https://api.github.com/repos/docker/compose/releases/latest | jq .name -r)
+
+# Output some info on what this is going to do
+echo "Note: docker-compose version $VERSION will be downloaded from:"
+echo "https://github.com/docker/compose/releases/download/${VERSION}/docker-compose-$(uname -s)-$(uname -m)"
+echo "Enter sudo password to install docker-compose"
+
+# Download and install lastest docker compose
+sudo curl -L https://github.com/docker/compose/releases/download/${VERSION}/docker-compose-$(uname -s)-$(uname -m) -o $DESTINATION
+sudo chmod +x $DESTINATION
+
+# Output new docker-compose version info
+echo ""
+docker-compose version
+```
+
+Running the script above will look like:
+
+```zsh
+$ vi update-docker-compose
+$ chmod u+x update-docker-compose
+$ ./update-docker-compose
+Note: docker-compose version 1.24.0 will be downloaded from:
+https://github.com/docker/compose/releases/download/1.24.0/docker-compose-Linux-x86_64
+Enter sudo password to install docker-compose
+  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
+                                 Dload  Upload   Total   Spent    Left  Speed
+100   617    0   617    0     0   1778      0 --:--:-- --:--:-- --:--:--  1778
+100 15.4M  100 15.4M    0     0  2478k      0  0:00:06  0:00:06 --:--:-- 2910k
+
+docker-compose version 1.24.0, build 0aa59064
+docker-py version: 3.7.2
+CPython version: 3.6.8
+OpenSSL version: OpenSSL 1.1.0j  20 Nov 2018
+```