dmxaddinput: 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/dmxaddinput - from package: xorg-x11-server-Xdmx

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

On Debian possible default full paths are:

/usr/bin/dmxaddinput - from package: xdmx-tools

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

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