drbl-rm-user: 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/drbl-rm-user - from package: drbl

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

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