lokkit: 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/sbin/lokkit - from package: system-config-firewall-base

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

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