night_flats: 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/night_flats - from package: nightview-cli

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

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