ipnadmin: 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/ipnadmin - from package: ion

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

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