nm_mgr: 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_mgr - from package: ion

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

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