nxauth: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/nxauth - from package: nxauth
/usr/lib64/nx/bin/nxauth - from package: nxauth

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