NoiseFilterGaussian: 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/NoiseFilterGaussian - from package: topp

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

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