nef.x: 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/nef.x - from package: palp

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

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