wlock: 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/wlock - from package: sendfile

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

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