dnssec-signzone: 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/dnssec-signzone - from package: bind

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

On Debian possible default full paths are:

/usr/sbin/dnssec-signzone - from package: bind9utils

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

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