Raspberrypi 3b boot from card & rootfs on USB SSD

I have Raspbeery Pi -3B & USB SSD, I want boot partition on SD card & RootFS partition on USB SSD. So to get this result I have downloaded current RasspberryPI OS (Lite) on SD card & on USB SSD (flash on both). After that I edit comandline.txt on sd card & divert rootfs partition towards /dev/sda2. System was booted & acquire USB SSD. So everything working according to my wish. But every one or two days later my raspberry offline & not responsive to anything. My system is working Headless & I have installed Homeassistant on it. So my whole system is offline everyday. I have just option left to remove power & put it back for booting. Any body please guide me where you think the problem is? I am using genuine raspberry pi power supply. Even I have put HDMI wire on hangining system, there is no display at all. As dietpi is similar to rasbian lite so i thought the expert from dietpi can also help me or in past any user from dietpi facing same type of trouble. thanks

Do I understood it correctly, you are using plain RasspberryPI OS (Lite) and not DietPi? You could have a look into /var/log directory if there are log files present containing any useful information regarding the crash. As well you could change the power supply. And use an own power supply for your external HDD.

Thanks Joulinar,
I like to move toward dietpi as i am much familiar with this operating system,
"
sudo -i

apt-get install -y software-properties-common apparmor-utils apt-transport-https avahi-daemon ca-certificates curl dbus jq network-manager

systemctl disable ModemManager

systemctl stop ModemManager

curl -fsSL get.docker.com | sh

curl -sL “https://raw.githubusercontent.com/Kanga-Who/home-assistant/master/supervised-installer.sh” | bash -s – -m raspberrypi3
"

https://community.home-assistant.io/t/installing-home-assistant-supervised-on-raspberry-pi-os/201836

to install a homeassistant supervisor i have to give these commands, i try these commands on dietpi first & system not able to run these commands. but these command happily works on rasbian lite, do you able to see which thing makes these commands not allowed to run on dietpi . if it is possible i will migrate to dietpi rather than other operating system if we able to execute these commands on dietpi.

Installing Home Assistant from dietpi-software is not an option? https://dietpi.com/forum/t/dietpi-software-details-for-all-installation-options/22/113
As well Docker is available from dietpi-software directly.

In generell DietPi for Raspberry Pi is based on Raspberry OS as well. But quite some packages are removed (that’s why it is Diet :wink: ) from plain Raspberry OS during transformation into DietPi. Therefore some thinks are not working same way. Like NetworkManager, it’s missing on DietPi because it’s not used by DietPi. However it could be installed if needed by yourselves. BUT it will conflict with dietpi-config network configuration and you would need to use NetworkManager for all network related stuff.