radwatch: 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/radwatch - from package: freeradius

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

On Debian possible default full paths are:

/usr/sbin/radwatch - from package: freeradius

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

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