unbound-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/sbin/unbound-control - from package: unbound

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

On Debian possible default full paths are:

/usr/sbin/unbound-control - from package: unbound

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

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