owexternal: 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/owexternal - from package: owserver

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

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