pam-auth-update: 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 Debian possible default full paths are:

/usr/sbin/pam-auth-update - from package: libpam-runtime

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

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