While having a great Latin America coffee from Ecuador I came to realize that I did not remember how to check Linux OS version using the command line.
Below are some examples for finding your Linux OS version. Open your command line:
/etc/os-release file
Type the following command using cat in Debian based distros:
cat /etc/os-release
I got the below result in my terminal:

/proc/version file
Using cat /proc/version worked for me for both Debian and Red Hat distros. Simply run:
cat /proc/version
And you should get the below result:
Linux version 4.4.0-198-generic (buildd@lgw01-amd64-051) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.12) )
Other commands to find Linux OS version
Try running in your terminal the below commands and experiment to see what output you get. If your Linux distro does not support it you should get a “command not found” error.
cat /etc/issue
hostnamectl
uname -a
lsb_release -a (mainly for Debian distros)