dfbscreen: 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/dfbscreen - from package: directfb

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

On Debian possible default full paths are:

/usr/bin/dfbscreen - from package: libdirectfb-bin

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

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