xasy: 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/xasy - from package: asymptote

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