rename: 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/rename - from package: util-linux-ng

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

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