drbl-get-netmask: 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/share/drbl/bin/drbl-get-netmask - from package: drbl

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

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