locker: 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/locker - from package: flowscan

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

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