mk-show-grants: 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/mk-show-grants - from package: maatkit

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

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