lunar: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/lunar - from package: lunar

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