drbd-overview: 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/sbin/drbd-overview - from package: drbd-utils

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

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