gamera_gui: command not found

Have You tried accessing the binary with the full path?

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/gamera_gui - from package: gamera-gui

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