fdnsip: 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/fdnsip - from package: firedns

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

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