rdx: 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/rdx - from package: nasm-rdoff

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

On Debian possible default full paths are:

/usr/bin/rdx - from package: nasm

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

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