cleankrf: 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/cleankrf - from package: dnssec-tools

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

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