usrp_x3xx_fpga_burner: 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 Debian possible default full paths are:

/usr/bin/usrp_x3xx_fpga_burner - from package: uhd-host

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

Error in other languages:
usrp_x3xx_fpga_burner: bevel nie gevind nie
usrp_x3xx_fpga_burner: comandă negăsită
usrp_x3xx_fpga_burner: comando não encontrado
usrp_x3xx_fpga_burner: commande introuvable
usrp_x3xx_fpga_burner: command not found
usrp_x3xx_fpga_burner: käsku ei ole
usrp_x3xx_fpga_burner: không tìm thấy lệnh
usrp_x3xx_fpga_burner: komanda nerasta
usrp_x3xx_fpga_burner: Kommando nicht gefunden.
usrp_x3xx_fpga_burner: kommandot finns inte
usrp_x3xx_fpga_burner: komut yok
usrp_x3xx_fpga_burner: nie znaleziono polecenia
usrp_x3xx_fpga_burner: níor aimsíodh an t-ordú
usrp_x3xx_fpga_burner: no se encontró la orden
usrp_x3xx_fpga_burner: no s'ha trobat l'ordre
usrp_x3xx_fpga_burner: opdracht niet gevonden
usrp_x3xx_fpga_burner: parancs nem található
usrp_x3xx_fpga_burner: perintah tidak ditemukan
usrp_x3xx_fpga_burner: príkaz nenájdený
usrp_x3xx_fpga_burner: příkaz nenalezen
usrp_x3xx_fpga_burner: команда не найдена
usrp_x3xx_fpga_burner: командата не е открита
usrp_x3xx_fpga_burner: 命令找不到
usrp_x3xx_fpga_burner: コマンドが見つかりません