radvdump: 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/radvdump - from package: radvd

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

On Debian possible default full paths are:

/usr/sbin/radvdump - from package: radvd

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

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