pdns_control: 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/pdns_control - from package: pdns

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

On Debian possible default full paths are:

/usr/bin/pdns_control - from package: pdns-server

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

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