radsecproxy: command not found

Have You tried accessing the binary with the full path?

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/sbin/radsecproxy - from package: radsecproxy

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