optirun: 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/optirun - from package: bumblebee

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

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