average_images: 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/lib/cmtk/bin/average_images - from package: cmtk

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

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