operon: 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/operon - from package: exfalso

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

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