zonesigner: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/zonesigner - from package: dnssec-tools

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