nm_agent: 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/nm_agent - from package: ion

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

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