mckey: 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/mckey - from package: librdmacm-utils

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

On Debian possible default full paths are:

/usr/bin/mckey - from package: rdmacm-utils

You may install the required package with command apt-get install {package}

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