I am having the same issue and have not found any solution yet.
HASS.IO is currently running in my house on a Debian 9.5 VM hosted in Win10 HyperV. Just got my hands on a better PC and was trying to bypass Win10 and dedicate a Debian OS for HASS.IO. May need to go down to 9.5 Stretch.
Thanks for the info.
I am just playing with this at the moment so if I don’t get any better ideas I may just try things and see what happens. Worst case is I break it and have to reinstall with 9.5 which is no great loss as I am using it on an old laptop which is dedicated for this experiment 
Peter
I have the same Issue when trying to install Hassio on my NUC.
Weird: Bevor installing to the NUC, I installed it within a Hyper-V VM with Debian 10, and that worked. Could it be Hardware related?
Well, actually I don´t know what I have done. I reinstalled the requirements, although every component told me that it was already installed and uptodate. Then, I used the script
curl -sL “https://raw.githubusercontent.com/home-assistant/hassio-installer/master/hassio_install.sh” | bash -s – -m intel-nuc
and it workd suddenly.
For anyone who comes across this issue at a later time, here is the cause and the solution.
It appears a change was made in Debian 10 in how the su command works when switching to root. It does not seem to correctly set PATH on login. This causes a lot of things to fail in weird ways, including the detection for the avahi-daemon package.
Details on the missing Path.
https://linuxconfig.org/command-not-found-missing-path-to-sbin-on-debian-gnu-linux
Quick Fix:
Use “su -” to switch to the root user. This set the PATH correctly and the install now worked without issue.
Now can I have the hour back it took to figure that out…
I can’t login as root anyway… su -l asks for a password and I never set a root password.
I can run commands as sudo
Also if I do sudo su… it logs me in as root anyway. I originally (on stretch) used sudo with the command to install hassio…
I hit that small bump as well with avahi-daemon wile installing Hass.io on a clearfog base.
The way I got around it was to download the install script and comment out the line:
command -v avahi-daemon > /dev/null 2>&1 || { echo "[Error] Please install avahi first"; exit 1; }
Then run the script. No problems after that.
One more way to get around the bump.
Hope its of help.
Thanks this fixed that issue for me.
This also worked for me when installing on debian 10. Thanks
This might be a better solution:
Debian installs avahi-daemon in a different location.
For me the path was /usr/sbin. This can be found with whereis avahi-daemon
So, I added it to my PATH using:
PATH=$PATH:/usr/sbin
Now command -v avahi-daemon resolves properly.
Thanks a lot. That actually solved the problem in my case.
How about to set this PATH like that in installation script, so all Debian 10 users won’t face same issue?
I submitted a pull request on GitHub, but they rejected it saying they’re working on a more permanent solution.
Hi,
Having just installed Debian 10 on a VM (via QNAP Virtulisation Station), I thought I’d have a go at installing HASS.IO - however, following the installation instructions - https://www.home-assistant.io/hassio/installation/ - it’s not clear if I’m supposed to run the very first command or not for Debian (admittedly it only references Ubuntu)
sudo add-apt-repository universe
Becuase when I run it, it returns this - “error ‘universe’ invalid”
I know great start hey?! - but what did you guys do ?
Because that is not a debian repository, but a ubuntu one. So no need to run it.
Doesn’t it specifically say Ubuntu only for that package?
Yep, agreed hence why I mentioned that in my post; just curious as Ubuntu is a distribution based on Debian, i’m never quite sure where the line is drawn, as I’ve often used Ubuntu guides to install/configure things on my Debian builds.
Hi,
Following the installation instructions for Debian, does anyone have any idea how I progress further , I can’t seem to get Docker installed
[email protected]:~# curl -fsSL get.docker.com | sh
# Executing docker install script, commit: 442e66405c304fa92af8aadaa1d9b31bf4b0ad94
+ sh -c apt-get update -qq >/dev/null
W: GPG error: http://ppa.launchpad.net/mosquitto-dev/mosquitto-ppa/ubuntu focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5E64E247262C4500
E: The repository 'http://ppa.launchpad.net/mosquitto-dev/mosquitto-ppa/ubuntu focal InRelease' is not signed.
[email protected]:~# curl -sL "https://raw.githubusercontent.com/home-assistant/supervised-installer/master/installer.sh" | bash -s
[Error] Please install docker first
Run the following command and adding the PUBKEY provided in the earlier error message worked for me -
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 5E64E247262C4500
Looks like you didn’t follow the Debian docker instructions but Ubuntu? (Ubuntu is the default I think and you click on a Debian tab on that install page)