canonical-certification-server: 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/canonical-certification-server - from package: checkbox-ng

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

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