ggthumb: 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/ggthumb - from package: geogebra-gnome

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

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