rtmpsrv: 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/rtmpsrv - from package: rtmpdump

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

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