u3-tool: 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/sbin/u3-tool - from package: u3-tool

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

Error in other languages:
u3-tool: bevel nie gevind nie
u3-tool: comandă negăsită
u3-tool: comando não encontrado
u3-tool: commande introuvable
u3-tool: command not found
u3-tool: käsku ei ole
u3-tool: không tìm thấy lệnh
u3-tool: komanda nerasta
u3-tool: Kommando nicht gefunden.
u3-tool: kommandot finns inte
u3-tool: komut yok
u3-tool: nie znaleziono polecenia
u3-tool: níor aimsíodh an t-ordú
u3-tool: no se encontró la orden
u3-tool: no s'ha trobat l'ordre
u3-tool: opdracht niet gevonden
u3-tool: parancs nem található
u3-tool: perintah tidak ditemukan
u3-tool: príkaz nenájdený
u3-tool: příkaz nenalezen
u3-tool: команда не найдена
u3-tool: командата не е открита
u3-tool: 命令找不到
u3-tool: コマンドが見つかりません