cdfnan: 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/cdfnan - from package: cdftools

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

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