optical_detect: 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

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/lib/plainbox-providers-1/checkbox/bin/optical_detect - from package: plainbox-provider-checkbox

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