gphoto2: 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/gphoto2 - from package: gphoto2

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

Error in other languages:
gphoto2: bevel nie gevind nie
gphoto2: comandă negăsită
gphoto2: comando não encontrado
gphoto2: commande introuvable
gphoto2: command not found
gphoto2: käsku ei ole
gphoto2: không tìm thấy lệnh
gphoto2: komanda nerasta
gphoto2: Kommando nicht gefunden.
gphoto2: kommandot finns inte
gphoto2: komut yok
gphoto2: nie znaleziono polecenia
gphoto2: níor aimsíodh an t-ordú
gphoto2: no se encontró la orden
gphoto2: no s'ha trobat l'ordre
gphoto2: opdracht niet gevonden
gphoto2: parancs nem található
gphoto2: perintah tidak ditemukan
gphoto2: príkaz nenájdený
gphoto2: příkaz nenalezen
gphoto2: команда не найдена
gphoto2: командата не е открита
gphoto2: 命令找不到
gphoto2: コマンドが見つかりません