owl: 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/owl - from package: owl

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

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