gtf: 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 CentOS possible default full paths are:

/usr/bin/gtf - from package: xorg-x11-server-Xorg

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/gtf - from package: xserver-xorg-core

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

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