ntpsweep: 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/ntpsweep - from package: ntp

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

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