rs6: 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/rs6 - from package: ipv6toolkit

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

Error in other languages:
rs6: bevel nie gevind nie
rs6: comandă negăsită
rs6: comando não encontrado
rs6: commande introuvable
rs6: command not found
rs6: käsku ei ole
rs6: không tìm thấy lệnh
rs6: komanda nerasta
rs6: Kommando nicht gefunden.
rs6: kommandot finns inte
rs6: komut yok
rs6: nie znaleziono polecenia
rs6: níor aimsíodh an t-ordú
rs6: no se encontró la orden
rs6: no s'ha trobat l'ordre
rs6: opdracht niet gevonden
rs6: parancs nem található
rs6: perintah tidak ditemukan
rs6: príkaz nenájdený
rs6: příkaz nenalezen
rs6: команда не найдена
rs6: командата не е открита
rs6: 命令找不到
rs6: コマンドが見つかりません