refdbsru: 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/refdbsru - from package: refdb-clients

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

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