create local ubuntu update repository with apt-mirror package

1. install apt-mirror package
# apt-get update
# apt-get install apt-mirror

2. modify apt-mirror configuration file (example for 12.04)
# vim /etc/apt/mirror.list

############# config ##################
#
set base_path    /var/spool/apt-mirror
#
set mirror_path  $base_path/mirror
set skel_path    $base_path/skel
set var_path     $base_path/var
# set cleanscript $var_path/clean.sh
# set defaultarch  
# set postmirror_script $var_path/postmirror.sh
# set run_postmirror 0
set nthreads     20
set _tilde 0
#
############# end config ##############

deb http://archive.ubuntu.com/ubuntu precise main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu precise-updates main restricted universe multiverse

deb-amd64 http://archive.ubuntu.com/ubuntu precise main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu precise-updates main restricted universe multiverse

deb-i386 http://archive.ubuntu.com/ubuntu precise main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu precise-updates main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu precise-proposed main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu precise-backports main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu precise-proposed main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu precise-backports main restricted universe multiverse

deb-src http://archive.ubuntu.com/ubuntu precise main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu precise-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu precise-proposed main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu precise-backports main restricted universe multiverse

clean http://archive.ubuntu.com/

3. initial apt-mirror

# /etc/init.d/apt-mirror

4. mkdir softlink in apache root directory
# ln -s /var/spool/apt-mirror/mirror/archive.ubuntu.com/ubuntu/ /var/www/ubuntu

5. modify client or server source.list direct to this server
# vim /etc/apt/source.list
change all hostname to this url

deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted

deb http://update.csp.com/ubuntu/ precise main restricted
deb-src http://update.csp.com/ubuntu/ precise main restricted