dtck: 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/bin/dtck - from package: dnssec-tools

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

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