njb-sendfile: 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/bin/njb-sendfile - from package: libnjb-tools

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

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