dmxrmscreen: 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/dmxrmscreen - 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/dmxrmscreen - from package: xdmx-tools

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

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