dnstrace: 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/dnstrace - from package: ndjbdns

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

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