keychecker: 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/keychecker - from package: keychecker

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

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