sdf2fps: 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/sdf2fps - from package: python-chemfp

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

Error in other languages:
sdf2fps: bevel nie gevind nie
sdf2fps: comandă negăsită
sdf2fps: comando não encontrado
sdf2fps: commande introuvable
sdf2fps: command not found
sdf2fps: käsku ei ole
sdf2fps: không tìm thấy lệnh
sdf2fps: komanda nerasta
sdf2fps: Kommando nicht gefunden.
sdf2fps: kommandot finns inte
sdf2fps: komut yok
sdf2fps: nie znaleziono polecenia
sdf2fps: níor aimsíodh an t-ordú
sdf2fps: no se encontró la orden
sdf2fps: no s'ha trobat l'ordre
sdf2fps: opdracht niet gevonden
sdf2fps: parancs nem található
sdf2fps: perintah tidak ditemukan
sdf2fps: príkaz nenájdený
sdf2fps: příkaz nenalezen
sdf2fps: команда не найдена
sdf2fps: командата не е открита
sdf2fps: 命令找不到
sdf2fps: コマンドが見つかりません