xcrysden: 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/xcrysden - from package: xcrysden

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

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