Booting Raspberry Pi 3 Model B from SSD

Sergio Guillen — Sun, 18 Jan 2026 20:19:47 +0000

This was originally posted on my personal blog:
https://blog.donkeysharp.xyz/boot-rpi-3-model-b-from-ssd/

Hey everyone! In this post I'm going to share my experience of USB booting the Raspberry Pi 3 Model B from an SSD. Although it is something I did almost one year ago, I wanted to share it... sorry for the 1 year delay xD!

Probably there might be something I missed on my solution, so any feedback is really appreciated!

Before the pandemic started, a friend of mine sold me 4 Raspberry Pi 3 Model B and one Raspberry Pi 3 Model B+. I used them for an electronics + home automation project I no longer need anymore, so I decided to repurpose them to something new, a new project I started working on for which I will make another blog entry.

This time, as I was not going to use the RPIs for electronics, instead something that will require more disk usage, I wanted to try something I personally hadn't tried before. I wanted to boot the RPIs from an SSD. Instead of spending money on new reliable, fast SD cards, I decided to use some spare SSDs I had instead. This is definitely something that was done before, but in my case there were some nuances that took me some days to realize how to fix them, and I wanted to share that experience with you.

What I used

For this experiment I used:

4 RPI 3 Model B
1 RPI 3 Model B+
5 Power supplies with the proper voltage and amps
5 Solid State Drives
5 USB to Sata adapters

Booting from SSD

There are multiple blog posts, forum entries and now LLMs that explain how to boot a RPI from an SSD (I added references I used in the references section below). In summary the steps required for RPI 3 Model B to USB boot from SSD are the next:

Using an SD card with RaspberryPI OS installed, run a full upgrade:

  sudo apt update -y && sudo apt full-upgrade -y

The following command will give two possible results depending on whether USB boot is enabled or not:

  vcgencmd otp_dump | grep 17
  17:1020000a <<<< it means USB boot is disabled
  17:3020000a <<<< it means USB boot is enabled

In case it is disabled, the way to enable it is by adding the following lines to the /boot/firmware/config.txt. Some tutorials mention the /boot/config.txt but those are outdated.

  program_usb_boot_mode=1
  program_usb_boot_timeout=1

Finally, clone the content of the SD card that has RaspberryPI OS to the SSD, you can do that with dd:

  # /dev/mmcblk0 is the SD card in my case
  # /dev/sdb is the SSD connected via USB
  dd if=/dev/mmcblk0 of=/dev/sdb status=progress

Then remove the SD card from the RPI, connect the SSD via USB and reboot.
Congrats! You booted your RPI from USB and an SSD. Now you can resize and stuff.

That's the result I wished I had, but no, it didn't work for 4 of my 5 RaspberryPIs. Let me tell you how I fixed-ish it.

The difference between RPI3 model B and RPI3 model B+

I executed the previous steps first (by coincidence on the RPI 3 Model B+). And it worked like a charm. Then for the next RPIs 3 Model B (not B+) it didn't work, I tried all of the 4 RPIs with the same result. I made sure I added the program_usb_boot_timeout=1 setting to the /boot/firmware/config.txt file to increase the wait for RPI to detect the disk, even with that verification it didn't work. No USB boot for the RPIs 3 Model B.

At that point, I got to the conclusion that at least in terms of booting, the RPI 3 Model B and RPI 3 Model B+ have differences.

My Solution (a fluke)

After trying multiple combinations that didn't work, it booted! I checked in the terminal and indeed, it booted from SSD. I executed some IO speed tests to make sure it was indeed using the SSD. It finally worked!

The new problem was I didn't add any new configuration change xD, so I was very confused on why it worked. And I noticed that this time I forgot to remove the SD card. Both SD and USB SSD were connected.

My hypothesis was that for RPI 3 Model B, an SD card is still required to boot, no matter if the operating system is installed on a USB SSD.

To finally verify that hypothesis, I formatted the SD card and just copied the content of the /boot/ directory from the SSD, actually they must be the same.

Voila! It booted again!

With that test, I was sure that the RPI 3 Model B requires an SD card to boot no matter where the OS is located.

I used the SD cards from my old project, formatted them and copied the content of /boot/firmware from each SSD and it worked fine.

It is important not to copy the content of the /boot/firmware directory from one SSD to all the SD cards, as each SSD has a different UUID specified in the /boot/firmware/cmdline.txt file. Copy from each SSD or make sure the /boot/firmware/cmdline.txt has the proper values for the disk UUID.

One example of the cmdline.txt

console=serial0,115200 console=tty1 root=PARTUUID=e000a75d-02 rootfstype=ext4 fsck.repair=yes rootwait cfg80211.ieee80211_regdom=US cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory

Upgrading the operating system

All the steps that I mentioned before happened when the latest RaspberryPI OS was based on Debian 12. Now the latest version of the RaspberryPI OS was released based on Debian 13, I decided that instead of formatting and doing the same process from scratch, I will follow the steps to do a RaspberryPI OS major upgrade.

These are the steps I follow for this matter:

Edit /etc/apt/sources.list and /etc/apt/sources.list.d/raspi.list and change from bookworm to trixie.
Run apt update to refresh the package indexes
Run apt install -y apt dpkg to install the latest version of the package manager.
Run apt upgrade --without-new-pkgs to install latest version without installing new dependencies. Make sure everything is fine.
Finally apt full-upgrade
Reboot

That would be enough on any setup (it works on the RPI 3 Model B+), but in this case as we boot from the SD card first and not the SSD, we will need to follow some extra steps.

Let's recall some Linux theory: The Linux kernel image is located at the /boot directory, but in our case the RPI boots from SD. We still have the boot content from the previous installation. After the upgrade when I rebooted, the kernel was still 6.1 and not 6.12 which is the one that comes with Debian 13.

In order to have the upgrade 100% ready, I had to repeat the previous steps I did to make the RPI boot from SSD.

Mount the SD card mount /dev/mmcblk0p1 /mnt/sdboot/,
Copy /boot/firmware from SSD to the SD card: cp -r /boot/firmware/* /mnt/sdboot/
Reboot

After I followed those steps, I was able to have the upgrade 100% functional.

If you want to use containers

In case you want to use containers or a container orchestrator such as K3S, make sure that the fields cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory are set in the /boot/firmware/cmdline.txt

Forem: Sergio Guillen