pyro-ns: 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/pyro-ns - from package: pyro

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

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