f3write: 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/f3write - from package: f3

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

On Debian possible default full paths are:

/usr/bin/f3write - from package: f3

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

Error in other languages:
f3write: bevel nie gevind nie
f3write: comandă negăsită
f3write: comando não encontrado
f3write: commande introuvable
f3write: command not found
f3write: käsku ei ole
f3write: không tìm thấy lệnh
f3write: komanda nerasta
f3write: Kommando nicht gefunden.
f3write: kommandot finns inte
f3write: komut yok
f3write: nie znaleziono polecenia
f3write: níor aimsíodh an t-ordú
f3write: no se encontró la orden
f3write: no s'ha trobat l'ordre
f3write: opdracht niet gevonden
f3write: parancs nem található
f3write: perintah tidak ditemukan
f3write: príkaz nenájdený
f3write: příkaz nenalezen
f3write: команда не найдена
f3write: командата не е открита
f3write: 命令找不到
f3write: コマンドが見つかりません