kflux.kss: 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/kflux.kss - from package: kdeartwork-screensavers

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

On Debian possible default full paths are:

/usr/bin/kflux.kss - from package: kscreensaver

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

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