check_forensic: 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/sbin/check_forensic - from package: apache2-utils

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

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