rtmpsuck: 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/rtmpsuck - from package: rtmpdump

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

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