binwalk: 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/binwalk - from package: binwalk

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

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