Upgrading to Debian 11 Quick

2021.05.27 - Nat Tuck - ~3 Minutes

The Debian Wiki provides some instructions to upgrade to a new release, but for systems with a lot of packages installed the process can be really slow.

Here’s the process I use to upgrade to a new Debian release.

Step 1: Disable Non-Debian Repositories

sources in sources.list.d

Look for third-party repos and disable them:

$ sudo su -
# cd /etc/apt
# ls sources.list.d
source1.list
source2.list
...

For each one of those apt sources, we want to open it up with a text editor and comment out the source lines.

# ls sources.list.d
syncthing.list
# nano sources.list.d/syncthing.list

We want to comment out every line that specifies a “deb” source, so we go from this:

deb https://apt.syncthing.net/ syncthing stable

To this:

# deb https://apt.syncthing.net/ syncthing stable

Do this for for every file in sources.list.d

sources in sources.list

Once we’ve cleaned up that directory, next is the main sources.list file.

# pwd
/etc/apt
# nano sources.list

In this file, there are two kinds of sources: official Debian sources and more third-party sources.

# Official sources frequently are at debian.org, like this one:
deb http://ftp.us.debian.org/debian/ buster main

# Sometimes they're from official mirror servers like this one:
deb http://debian.csail.mit.edu/debian/ buster main

# This is definitely a third party repository:
deb http://emacs.ganneff.de/ buster main

# And this isn't even a real debian repo, it's an Ubuntu PPA
#  - it says "ppa"
#  - it's at "launchpad.net"
#  - it has an Ubuntu codename ("impish"), not a Debian one (like "buster")
deb http://ppa.launchpad.net/kdenlive/kdenlive-stable/ubuntu impish main

In sources.list.d, we want to comment out:

Things that aren’t official Debian repos.
All the lines that don’t start with “deb” (e.g. “deb-src”). They just slow things down for the update.

Step 2: Install current upgrades

$ sudo apt update -y
$ sudo apt upgrade  -y
$ sudo apt autoremove -y

Step 3: Switch your sources to the new Debian version

Back in sources.list.d, replace all instances of the old Debian version with the new one. To go to from Debian 10 to 11, this means replacing “buster” with “bullseye”.

$ sudo nano /etc/apt/sources.list.d

# Edit lines like this:
deb http://ftp.us.debian.org/debian/ buster main
deb http://debian.csail.mit.edu/debian/ buster main

# To be lines like this:
deb http://ftp.us.debian.org/debian/ bullseye main
deb http://debian.csail.mit.edu/debian/ bullseye main

Step 4: Do the upgrade

First, let’s install a tool to speed up the process:

$ sudo apt install eatmydata

The eatmydata command runs another command, but skips all the steps where that command tries to force data to really be written to disk. The Debian dpkg tool forces disk rights frequently to avoid creating an unbootable system if the machine crashes, but this is really slow with hundreds of packages.

Losing power in the middle of the next step would be bad - it might leave the computer unbootable - but that problem can be easily fixed by booting from a thumb drive and this doesn’t risk user data at all.

really do the upgrade

This step will take like an hour, and will occasionally stop to ask dumb questions.

$ sudo eatmydata apt update -y 
$ sudo eatmydata apt full-upgrade -y
$ sudo eatmydata apt autoremove -y

Handling dumb questions:

Do you want to restart services? Yes.
Do you want to install the package maintainer’s version of the config file? Yes, unless you recognize it.

Step 5: Reboot

$ sudo reboot

When the machine comes back up, you should be done.