snntpd: 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

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/snntpd - from package: sn

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