rfddump: 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/rfddump - from package: mtd-utils

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

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