buildrealms: 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/buildrealms - from package: dnssec-tools

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

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