mkxauth: 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/mkxauth - from package: xorg-x11-xauth

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

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