unbound: 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 - from package: unbound

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

On Debian possible default full paths are:

/usr/sbin/unbound - from package: unbound

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

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