nghttpd: 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 Debian possible default full paths are:

/usr/sbin/nghttpd - from package: nghttp2

You may install the required package with command apt-get install {package}

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