pamstack: 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/pamstack - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pamstack - from package: netpbm

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

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