ntpdc: 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 CentOS possible default full paths are:

/usr/sbin/ntpdc - from package: ntp

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ntpdc - from package: ntp

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

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