LE boot problem with 2-in-1 Dual Micro SD Switcher on Raspberry Pi 4

  • Hi!

    I just bought this switcher and I have a problem. My RPi4 is booting LE from both SD cards inserted in the switcher but only when LE is installed on a SanDisk 16GB and a Kingston 16GB.

    It doesn't boot from Samsung Evo+ 32GB. I even tried with only the Samsung card inserted in the switcher, in both positions, no boot.

    It starts booting LibreELEC, the LE logo is appearing on the screen and right after I get an error message related to mounting problems or something like that (I can take a picture with the error messages if needed).

    LE is booting from the same Samsung SD card if I insert the SD card directly in RPi (without using the switcher) so I know the SD card is good.

    I don't have other SD cards to test so I could not figure it out what is the problem. Anyone knows why it's happening this?

    Thank you!

  • check the label of the mmc0blkp0 partition on the SDcard. it should match what the error is saying.

    I am sorry, I don't know what this is and what should I check. X/

    The same card is working when inserted directly in RPi4.

    • Official Post

    use the "blkid" command to check the disk label. You can do this with LibreELEC but because you don't have a booting system you may have to put the sdcard in another PC (linux). Or boot your RPi with a working sdcard and use a usb to sd converter to plug the faulty sdcard at the same time. You should see something like this.

    # blkid
    /dev/mmcblk0p1: SEC_TYPE="msdos" LABEL_FATBOOT="SYSTEM" LABEL="SYSTEM" UUID="2303-0357" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="4cb80fca-01"
    /dev/mmcblk0p2: LABEL="STORAGE" UUID="66f7dd29-b2bc-41b1-aee4-74fd08640153" BLOCK_SIZE="1024" TYPE="ext4" PARTUUID="4cb80fca-02"

    The other thing to check is what your cmdline.txt file says in in the root of your sdcard. it should look similar to this.

    boot=UUID=2303-0357 disk=UUID=66f7dd29-b2bc-41b1-aee4-74fd08640153 ssh debugging

    As you can see I'm using UUID's (which is the default). So you have a mismatch somewhere.

  • use the "blkid" command to check the disk label. You can do this with LibreELEC but because you don't have a booting system you may have to put the sdcard in another PC (linux).

    1. I formatted and flashed again LE on the Samsung SD card. I inserted it first directly in RPi4 and started LE. This what I get using ssh:

    LibreELEC:~ # blkid
    /dev/mmcblk0: PTUUID="ee03917a" PTTYPE="dos"
    /dev/mmcblk0p1: SEC_TYPE="msdos" LABEL_FATBOOT="LIBREELEC" LABEL="LIBREELEC" UUID="2410-0508" TYPE="vfat" PARTUUID="ee03917a-01"
    /dev/mmcblk0p2: LABEL="STORAGE" UUID="09814adf-0b3e-462b-ad3f-abd8815b9b92" TYPE="ext4" PARTUUID="ee03917a-02"
    /dev/loop0: TYPE="squashfs"
    LibreELEC:~ #

    2. I booted Ubuntu on my computer from a USB stick. I inserted the SD card in the reader and I opened the cmdline.txt from LibreELEC. it is looking like this:

    boot=UUID=2410-0508 disk=UUID=09814adf-0b3e-462b-ad3f-abd8815b9b92 quiet 

    3. I inserted the same SD card in the switcher and I started RPi. After the rainbow square the screen stays black for 20-30 seconds after I get this message:

    *** Error in mount_flash: mount_common: Could not mount UUID=2410-0508 ***
    ### Starting debugging shell for boot step: mount_flash... type exit to quit ###
  • perhaps the sdcard just isn't compatible with that device.

    Very possible but it would be good to find out why, just to know what kind of SD cards I need for it to work.

    I did another test. I added sdhci.debug_quirks2=4 in cmdline.txt:

    boot=UUID=2410-0508 disk=UUID=09814adf-0b3e-462b-ad3f-abd8815b9b92 sdhci.debug_quirks2=4 quiet

    This way LibreELEC started but only once. After restart LE doesn't boot again and I get this error message ...

    *** Error in mount_flash: mount_part: Unknown filesystem ***
    ### Starting debugging shell for boot step: mount_flash... type exit to quit ###

    ... and when I checked cmdline.txt it was empty, it doesn't had any line. :)

    I added the entire line in cmdline.txt and LE started. After restart it happened the same - it didn't boot and cmdline.txt was empty again.

    I don't know what does it means.

    What is the difference between these two SD cards apart from their capacity?

    SanDisk is working and Samsung doesn't work with the switcher with RPI4 8GB. Both of them are working when inserted directly in RPi.

    Edited once, last by racko: Merged a post created by racko into this post. ().

  • racko, this adapter has one chip on it - can you read what is it?

    Unfortunately it's unmarked.

    I ordered a SanDisk Ultra 16GB, I am curious if it's working. I couldn't find the same SanDisk Edge which I have and is working.

  • I bought a SanDisk Ultra 16GB, it's working like a charm with the switcher in RPi4.

    It would have been good to know the reason why other SD cards are not working but I'm done with it, two spare cards will be enough. :)