ksflatten: 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/ksflatten - from package: pykickstart

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

On Debian possible default full paths are:

/usr/bin/ksflatten - from package: python-pykickstart

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

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