arandr: 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 Debian possible default full paths are:

/usr/bin/arandr - from package: arandr

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

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