mightyctl: 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/mightyctl - from package: mighttpd2

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