drat: 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/drat - from package: drat-tools

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

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