htpdate: 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/htpdate - from package: htpdate

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

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