Raspberry Pi Upgrade from wheezy to jessie to stretch

RPi-Upgrade

# In-place upghrade from wheezy to jessie
# https://raspberrypi.stackexchange.com/questions/27858/upgrade-to-raspbian-jessie
# https://raspberrypi.stackexchange.com/questions/80029/how-to-complete-upgrade-from-wheezy-to-stretch

# Backup any files which are important to you.
# Ensure there is plenty of disk space free df -h

# With your new or existing install:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

# to make sure wheezy is fully up to date.

# Edit /etc/apt/sources.list and change wheezy to jessie.

sudo nano /etc/apt/sources.list

# Then update and upgrade again. Repeat for each major release (not recommended to skip any)

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

# repeat for In-place upghrade from wheezy to stretch

This takes a LONG time to run, even with high bandwidth internet. To make matters worse, there will likely be occasional prompts to overwrite config files. Probably should say yes unless you explicitly know otherwise; even then - probably best to save changes and apply to new config file. ymmv

This part in particular may take a VERY long time to run:

Starting dphys-swapfile swapfile setup ...
computing size, want /var/swap=1966MByte, checking existing: deleting wrong size file (104857600), generating swapfile ...