sunxi-fexc: 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/sunxi-fexc - from package: sunxi-tools

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

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