lxrandr: 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/lxrandr - from package: lxrandr

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

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