xtitle: 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/xtitle - from package: xtitle

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

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