realmset: 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/realmset - from package: dnssec-tools

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

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