checker: 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/checker - from package: spark

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

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