How to upgrade Debian 7 to Debian 8

ref: https://www.debian.org/releases/stable/i386/release-notes/ch-upgrading

checking system status:
1. make it full update
# apt-get update
# apt-get upgrade
2. disabling apt pinning /etc/apt/preferences.d or /etc/apt/preferences to allow new stable
3. check package status
# dpkg --audit
for aptitude
# aptitude search "~ahold"
for apt
# dpkg --get-selections | grep 'hold$'

remove unofficial source and add jessie repository in /etc/apt/sources.list

-------------------------
#

# deb cdrom:[Debian GNU/Linux 7.1.0 _Wheezy_ - Official amd64 CD Binary-1 20130615-23:06]/ wheezy main

#deb cdrom:[Debian GNU/Linux 7.1.0 _Wheezy_ - Official amd64 CD Binary-1 20130615-23:06]/ wheezy main

#deb http://security.debian.org/ wheezy/updates main
#deb-src http://security.debian.org/ wheezy/updates main
deb http://security.debian.org/ jessie/updates main
deb-src http://security.debian.org/ jessie/updates main

#deb http://kambing.ui.ac.id/debian/ wheezy main
#deb-src http://kambing.ui.ac.id/debian/ wheezy main
deb http://kambing.ui.ac.id/debian/ jessie main
deb-src http://kambing.ui.ac.id/debian/ jessie main

# wheezy-updates, previously known as 'volatile'
#deb http://kambing.ui.ac.id/debian/ wheezy-updates main
#deb-src http://kambing.ui.ac.id/debian/ wheezy-updates main

#deb http://http.debian.net/debian wheezy main
#deb-src http://http.debian.net/debian wheezy main

#deb http://http.debian.net/debian wheezy-updates main
#deb-src http://http.debian.net/debian wheezy-updates main

# Debian 7 (flash player adobe)
#deb http://ftp.de.debian.org/debian wheezy main contrib
#deb http://ftp.de.debian.org/debian wheezy main # duplicate

# Non Free Repository
#deb http://ftp.de.debian.org/debian wheezy main non-free
deb http://ftp.de.debian.org/debian jessie main non-free
-------------------------

add cd/dvd
1. verify cd/dvd
# mount /media/cdrom # this will mount the CD to the mount point
# ls -alF /media/cdrom # this should show the CD's root directory
# umount /media/cdrom # this will unmount the CD
2. add cd/dvd into apt
# apt-cdrom add

!MAKE SURE YOUR /etc/apt/sources.list refer either to “jessie”, no more wheezy

Start your upgrade
1. run
# apt-get update
if error appear "E: You don't have enough free space in /var/cache/apt/archives/."
# apt-get clean
# apt-get autoremove
2. minimal system upgrade
# apt-get upgrade
Must upgrade libc6 glibc
3. upgrade system
# apt-get dist-upgrade
4. use Package Updater to fix application update
5. add 3rd party repository

to fix and resume upgrade
# apt-get -f install

final repository /etc/apt/sources.list
#deb cdrom:[Debian GNU/Linux 8.0.0 _Jessie_ - Official amd64 CD Binary-1 2015042
5-12:54]/ jessie main

deb http://security.debian.org/ jessie/updates main
deb-src http://security.debian.org/ jessie/updates main

deb http://kambing.ui.ac.id/debian/ jessie main
deb-src http://kambing.ui.ac.id/debian/ jessie main

# Non Free Repository
deb http://ftp.de.debian.org/debian jessie main non-free

deb http://ftp.de.debian.org/debian jessie-backports main