rvnamed-ng: 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 CentOS possible default full paths are:

/usr/sbin/rvnamed-ng - from package: iptraf-ng

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/rvnamed-ng - from package: iptraf-ng

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

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