cvt: 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/cvt - 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/cvt - from package: xserver-xorg-core

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

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