dumpexfat: 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

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:

/sbin/dumpexfat - from package: exfat-utils

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