Boot from the microSD card

You can boot other Linux distributions, including another PureOS, from the microSD card. For example, you can install Mobian onto the microSD card and choose when to boot into it.

Warning

The overall experience of using the OS if it is booted from the microSD card will be noticeably slower than running from the internal storage.

How to boot

When powering on the device, hold the Volume-down button.

Installing the same image

If you put the same image onto the SD card as the internal eMMC storage, you will end up with multiple partitions with the same UUIDs. This may cause unexpected behavior during mounting in the boot process.

You can fix this by updating the partitions on the microSD card:

  1. Install wl-clipboard to copy values from commands.

    sudo apt install wl-clipboard

  2. Ensure the microSD card is not mounted.

  3. Change the UUID of the boot partition.

    sudo tune2fs -U random /dev/sda1

  4. Copy the generated UUID to the clipboard.

    sudo tune2fs -l /dev/sda1 | grep UUID | wl-copy

  5. Temporarily store this value somewhere like the Text Editor app.

  6. Change the UUID of the root partition.

    sudo tune2fs -U random /dev/sda2

  7. Copy the generated UUID to the clipboard.

    sudo tune2fs -l /dev/sda2 | grep UUID | wl-copy

  8. Temporarily store this value in the same place as before.

  9. Mount the root partition (/dev/sda2) of the microSD card.

    sudo mount /dev/sda2 /mnt/mysdcard

  10. Edit (as root) /mnt/etc/fstab (i.e. the /etc/fstab file that is on the microSD card) and replace the old UUID values. Put the saved UUID values on the line where the corresponding partition is mounted. The line that is mounting /boot for the first partition gets the first UUID value, and the line that is mounting / (root) for the second partition gets the second UUID value.

    For example, let’s say the first generated UUID for the boot partition is 9be41999-a89e-4ba9-af43-6b49f92d9932 and the second UUID for the root partition is 2d31dea7-39ed-4924-93ad-06b21114dc1c. The /mnt/etc/fstab file should look something like the following:

    UUID=2d31dea7-39ed-4924-93ad-06b21114dc1c / ext4 errors=remount-ro 0 1
UUID=9be41999-a89e-4ba9-af43-6b49f92d9932 /boot ext2 errors=remount-ro 0 2