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/sendfile - from package: sendfile

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

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