align_image_stack: 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/bin/align_image_stack - from package: hugin-tools

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

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