beep: 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/beep - from package: beep

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

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