One of my two new Yuns will not mount SD cards

I can't get one my new YUNs to recognize an SD card. Except for that, the YUN seems to do everything perfectly. My other YUN mounts SD cards properly. Even when I swap SD cards between YUNs running the same sketch the bad Yun won't mount it. However if I plug the same SC card into the large USB port using an adapter, the bad YUN mounts it properly and the sketchs like TemteratureWebPanel run without a problem. I have examined both YUNs using SSH in WinSCP and the bad YUN does not show any contents for the SD card. The other YUN does. Dmesg reports no activity when I plug or unplug the SD card from the microSD connector. Dmesg does report it on the working YUN. The SD cards are 16GB, FAT32 with an Arduier in the root.

I notice an interesting difference in the folder dates between the two YUNs. In my good YUN most of the folders have a date of 8/8/2013. However in my bad YUN most of the folders have a date of 11/22/2013. This is especially the case in the proc folder where I see many differences between the two YUNS. On 11/22/2013 I was running sketches in bad YUN that didn't use an SD card. Could something have reset the bad YUN's software and caused my problem? Is there a fix? I need help to use the microSD connector for data logging in both YUNs

HI F33A,

Facing the same issue!

I've tried several SD cards using different formats (FAT16 / FAT32 / EXT3 & EXT4) with folders "arduino/www" and "arduino/data" and sample files. Impossible to get the Yun to mount the SD cards. When I SSH the Yun and dmesg the only line regarding the SD is;

[  10.550000] sd 0:0:0:0: [sda] Attached SCSI removable disk

When I df the system with the SD inserted I get (after restart)

Filesystem           1K-blocks      Used Available Use% Mounted on
rootfs                    7680       620      7060   8% /
/dev/root                 7168      7168         0 100% /rom
tmpfs                    30568       104     30464   0% /tmp
tmpfs                      512         0       512   0% /dev
/dev/mtdblock3            7680       620      7060   8% /overlay
overlayfs:/overlay        7680       620      7060   8% /

When I ls -all /mnt/ I get

~# ls -all /mnt/
drwxr-xr-x    2 root     root             3 Aug 19 16:21 .
drwxr-xr-x    1 root     root             0 Dec 18 18:42 ..

I'm wondering if we're looking at defects on the Yun where the actual hardware is faulty...

My question; is there any way of checking that the actual physical SD reader is working correctly?

Hoping that someone from the designer team at Arduino can step in for more insight!



I did further testing with no success. I decided to return the Yun to the distributor. I purchased the microprocessor at play-zone in Switzerland. I contacted them to see what we could do. They asked me to return the faulty part so they could give a shot at it. They had no success mounting the SD.

Play-zone were friendly and helpful. They returned me "a tested by them" new Yun...

I believe that this issue should be looked into further by the designers at Arduino and to see if the company assembling the design have had similar faults on the boards.

Hope this helps to whom it may concern.


ls /dev/s*

should give you back something like below, if it is missing might be hardware problem.

/dev/sda  /dev/stderr  /dev/stdin   /dev/stdout

manage partitions, format, make mount point, mount on linino

opkg update
opkg install  fdisk  e2fsprogs 
fdisk /dev/sda
mke2fs -t ext4 /dev/sda1
mkdir -p /mnt/sda1
mount  /dev/sda1 /mnt/sda1

after reboot check mount.


The URL to help you howto use fdisk

hey, reading through this, I've had issues with sd cards. Thinking it could be faulty then.
When trying

ls /dev/s*

I get



The /dev/sda is in purple?

Any ideas?

EDIT: When I plugin a USB flash drive it increases to

/dev/sda   /dev/sdb   /dev/sdb1


Partition microSD:

fdisk /dev/sda