====== Upgrading Wheezy to Jessie ======

procedure to upgrade Debian from Wheezy to Jessie in a few simple steps.

Before you start with the upgrade, backup all critical data. Thats especially the config data in the /etc directory and the user data in /home. When you run a server then you should include the databases (MySQL, Postgresql, etc), web and email data in the backup as well. The backup should be stored on a external harddisk, on an external server e.g. by FTP or on a cloud drive. Here are a few examples on how to create backups with tar.
Backup the configuration and data

Configuration files in the /etc directory.

tar -pczf etc.tar.gz /etc

Backup of the /var/www website directory.

tar -pczf www.tar.gz /var/www

Backup of the /home directories.

tar -pczf home.tar.gz /home

For ISPConfig 3 users: Backup of your email server files.

tar -pczf vmail.tar.gz /var/vmail

Backup MySQL databases

mysqldump --defaults-file=/etc/mysql/debian.cnf -cCeQ --hex-blob --quote-names --routines --events --triggers --all-databases -r all_databases.sql

Then move the tar.gz and .sql files for safe storage on a backup drive.

 
Check the apt sources.list file

We will install all available Wheezy updates first before we upgrade to Jessie. On some systems the package source is defined as "stable" in the sources.list file instead of "wheezy" or "jessie". To avoid an accidential early upgrade to Jessie, please check the sources.list now and ensure that it contains "wheezy" and not "stable" as source:

Use a commandline editor like nano or vi to open /etc/apt/sources.list, the lines should be similar to the ones below:

nano /etc/apt/sources.list

deb http://ftp.de.debian.org/debian wheezy main contrib non-free
deb-src http://ftp.de.debian.org/debian wheezy main contrib non-free
deb http://ftp.de.debian.org/debian wheezy-updates main contrib non-free
deb http://ftp.de.debian.org/debian-security wheezy/updates main contrib non-free

Your country code is most likely not "de", you should use the code of your country here. Using your country code in the file will speed up the package download.

 
Update the packages for Wheezy

The following commands will install all pending Wheezy updates. This ensures that your system is in a good shape for the update to Jessie.

apt-get update

Ready for first upgrade:

apt-get upgrade

Follow this with:

apt-get dist-upgrade

 
Check the package state to ensure that no packages are on hold or in half installed state

This test is important, we will check the package state to ensure that no packages are on hold or in half installed state. Your system and apt database must be in a good shape before we proceed with the dist upgrade. If there are any broken or "on hold" packages, then fix these issues before the upgrade.

Check that no packages are on hold by querying the package database with the dpkg command:

dpkg --audit
dpkg --get-selections | grep hold

When both commands did not return any packages, then proceed with the upgrade.

 
Update the sources.list for Jessie

Edit the /etc/apt/sources.list file again:

nano /etc/apt/sources.list

and replace its content with the following lines:

deb http://ftp.de.debian.org/debian/ jessie main contrib non-free
deb-src http://ftp.de.debian.org/debian/ jessie main contrib non-free


deb http://httpredir.debian.org/debian jessie-updates main contrib non-free
deb-src http://httpredir.debian.org/debian jessie-updates main contrib non-free


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

Choose your nearest locale by replacing "de" with e.g. "us" or your country code. Then save the file and run the following command to update the sources database:

apt-get update

 
Jessie Upgrade in two steps

It is recommended to do the upgrade in two steps, first run "apt-get upgrade" to install the base packages and then run "apt-get dist-upgrade" to do the actual distribution upgrade,

Start with the update by running this command:

apt-get upgrade

Next we will do the distribution upgrade by running:

apt-get dist-upgrade

A reboot is required to finish the upgrade and load the new kernel:

reboot
Check the update

To check which Debian version is currently installed on the system, take a look at the file /etc/os-release.

cat /etc/os-release

The result on an Debian Jessie system is: