dvd-ram-control: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/dvd-ram-control - from package: dvd+rw-tools

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/dvd-ram-control - from package: dvd+rw-tools

You may install the required package with command apt-get install {package}

Error in other languages:
dvd-ram-control: bevel nie gevind nie
dvd-ram-control: comandă negăsită
dvd-ram-control: comando não encontrado
dvd-ram-control: commande introuvable
dvd-ram-control: command not found
dvd-ram-control: käsku ei ole
dvd-ram-control: không tìm thấy lệnh
dvd-ram-control: komanda nerasta
dvd-ram-control: Kommando nicht gefunden.
dvd-ram-control: kommandot finns inte
dvd-ram-control: komut yok
dvd-ram-control: nie znaleziono polecenia
dvd-ram-control: níor aimsíodh an t-ordú
dvd-ram-control: no se encontró la orden
dvd-ram-control: no s'ha trobat l'ordre
dvd-ram-control: opdracht niet gevonden
dvd-ram-control: parancs nem található
dvd-ram-control: perintah tidak ditemukan
dvd-ram-control: príkaz nenájdený
dvd-ram-control: příkaz nenalezen
dvd-ram-control: команда не найдена
dvd-ram-control: командата не е открита
dvd-ram-control: 命令找不到
dvd-ram-control: コマンドが見つかりません