ltpclock: 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/ltpclock - from package: ion

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

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