gcrystal: 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/gcrystal - from package: gcrystal

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

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