rtmpgw: 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/sbin/rtmpgw - from package: rtmpdump

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

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