nvramtool: 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/nvramtool - from package: nvramtool

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

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