xttitle: 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/xttitle - from package: xttitle

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

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