hwloc-diff: 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/hwloc-diff - from package: hwloc-nox
/usr/bin/hwloc-diff - from package: hwloc

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

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