Upgrade your Raspbian install from Jessie to Stretch.

Prepare

Get up to date.

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

Verify nothing is wrong. Verify no errors are reported after each command. Fix as required (you’re on your own here!).

$ dpkg -C
$ apt-mark showhold

Optionally upgrade the firmware.

$ sudo rpi-update    

Prepare apt-get

Update the sources to apt-get. This replaces “jessie” with “stretch” in the repository locations giving apt-get access to the new version’s binaries.

$ sudo sed -i 's/jessie/stretch/g' /etc/apt/sources.list    
$ sudo sed -i 's/jessie/stretch/g' /etc/apt/sources.list.d/raspi.list    

Verify this caught them all. Run the following, expecting no output. If the command returns anything having previously run the sed commands above, it means more files may need tweaking. Run the sed command for each.

$ grep -lnr jessie /etc/apt    

Speed up subsequent steps by removing the list change package.

$ sudo apt-get remove apt-listchanges

Do the Upgrade

$ sudo apt-get update && sudo apt-get upgrade -y
$ sudo apt-get dist-upgrade -y

Cleanup old outdated packages.

$ sudo apt-get autoremove -y && sudo apt-get autoclean

Verify with cat /etc/os-release.

Update Firmware

You’ve come this far, might as well get the latest firmware.

$ sudo rpi-update