oggSilence: 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/oggSilence - from package: oggvideotools

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

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