checkbox: 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/checkbox - from package: checkbox-ng

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

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