nvcompress: 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/nvcompress - from package: libnvtt-bin

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

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