ctnnetwork: 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/ctnnetwork - from package: ctn

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

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