volatility: 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/volatility - from package: volatility

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

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