mkntfs: 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:

/sbin/mkntfs - from package: ntfsprogs
/usr/sbin/mkntfs - from package: ntfsprogs

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

On Debian possible default full paths are:

/sbin/mkntfs - from package: ntfs-3g

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

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