ctn_version: 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/ctn_version - from package: ctn

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

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