please verify unrar installation instructions

I'm looking to see if the instructions are still correct for OMV 4.0, if something need to be change please let me know. Do i need to replace Jessie and wheezy to strech?

Backup your sources.list file
cp /etc/apt/sources.list /etc/apt/sources.list.bak Add a source to the sources.list
echo deb ftp.us.debian.org/debian/ jessie main >> /etc/apt/sources.list Add another source
echo deb ftp.us.debian.org/debian/ wheezy non-free >> /etc/apt/sources.list Update your package lists
apt-get update Install the required programs...Type y when asked if you would like to proceed with the installation and hit enter
apt-get install par2 unrarAnd finally let's revert the changes made to sources list
mv -f /etc/apt/sources.list.bak /etc/apt/sources.listYou should have unrar version 4.10

looks like it's available just not installed? so just apt-get install par2 unrar

root@openmediavault:~# apt-get install par2 unrar
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package unrar is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'unrar' has no installation candidate
root@openmediavault:~#

I did the following

echo deb http://ftp.us.debian.org/debian/ stretch non-free >> /etc/apt/sources.list

Then updated

apt-get update

tried to install using and it stil failed.

apt-get install par2 unrar

Found the mistake I forgot to add >>

Let me check into that. I have never seen that option before.

Now to figure out my unrar cron command again that i lost when i reformatted. Thanks for the assist