ffplugin: command not found

Have You tried accessing the binary with the full path?

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/ffplugin - from package: fawkes-core

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