drbl-swapfile: 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-swapfile - from package: drbl

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

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