xtrlock: 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/xtrlock - from package: xtrlock

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

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