freeDiameterd-1.1.2: 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 CentOS possible default full paths are:

/usr/bin/freeDiameterd-1.1.2 - from package: freeDiameter

You may install the required package with command yum install {package}
Error in other languages:
freeDiameterd-1.1.2: bevel nie gevind nie
freeDiameterd-1.1.2: comandă negăsită
freeDiameterd-1.1.2: comando não encontrado
freeDiameterd-1.1.2: commande introuvable
freeDiameterd-1.1.2: command not found
freeDiameterd-1.1.2: käsku ei ole
freeDiameterd-1.1.2: không tìm thấy lệnh
freeDiameterd-1.1.2: komanda nerasta
freeDiameterd-1.1.2: Kommando nicht gefunden.
freeDiameterd-1.1.2: kommandot finns inte
freeDiameterd-1.1.2: komut yok
freeDiameterd-1.1.2: nie znaleziono polecenia
freeDiameterd-1.1.2: níor aimsíodh an t-ordú
freeDiameterd-1.1.2: no se encontró la orden
freeDiameterd-1.1.2: no s'ha trobat l'ordre
freeDiameterd-1.1.2: opdracht niet gevonden
freeDiameterd-1.1.2: parancs nem található
freeDiameterd-1.1.2: perintah tidak ditemukan
freeDiameterd-1.1.2: príkaz nenájdený
freeDiameterd-1.1.2: příkaz nenalezen
freeDiameterd-1.1.2: команда не найдена
freeDiameterd-1.1.2: командата не е открита
freeDiameterd-1.1.2: 命令找不到
freeDiameterd-1.1.2: コマンドが見つかりません