mpathconf: 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:

/sbin/mpathconf - from package: device-mapper-multipath

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

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