cmk: 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/cmk - from package: check-mk

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

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