castor: 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/castor - from package: castor

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

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