bestfortress: 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:

/sbin/bestfortress - from package: nut

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

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