gnupod_convert_RIFF: 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/gnupod_convert_RIFF - from package: gnupod-tools

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

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