lights: 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/lights - from package: dnssec-tools

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

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