radtest: 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/bin/radtest - from package: freeradius-utils

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

On Debian possible default full paths are:

/usr/bin/radtest - from package: freeradius-utils
/usr/bin/radtest - from package: radiusd-livingston

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

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