ng: 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/ng - from package: ng-common

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

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