authconfig-tui: 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/authconfig-tui - from package: authconfig-gtk
/usr/sbin/authconfig-tui - from package: authconfig

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

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