How to replace an SD card

Versions: 2.5, 3.0

Applies to Platform: Mini ARM All
Last Update: 30 August 2013

This article aims to introduce the troubleshooting flow in order to detect if your Endian Appliance SD card is faulty and/or detected appropiately as a Sandisk card. It also introduces knowledge related to the new backup functionality available for NAND in ARM appliances and explains how to fix the SD card via the command line.

Backup functionality on NAND

Before proceeding further, first you have to be aware about the implications of NAND and the SD card. A backup policy exists which implies that a copy of the configuration from the SD card will be stored on NAND. Every 6 hours, the Endian Appliance will trigger a scheduled job which will store a backup of the configuration present on the SD card on its NAND in order to not lose the settings in case the SD card fails or is unplugged.

Check if the SD card is faulty

In order to check if the SD card is faulty, read this lesson and carefully follow the instructions provided there.

Verify if the SD card is Sandisk

In order to check the Vendor ID which should identify the card quality enter the following commands via SSH or Console directly on the Endian system:

root@endian:~ # cat /sys/block/mmcblk0/device/manfid
root@endian:~ # cat /sys/block/mmcblk0/device/oemid

If the output differs from the one shown above, the SD card is not an original Sandisk card and its quality may be lower.

How to reset Mini's SD card

The following instructions will reset the SD card by deleting the partition table using the Endian CLI.


Before proceeding, please remember that if you wish to reset the SD card, before you do so, make a backup and copy it to NAND so you will have the current configuration backed up and at your disposal (recommended), if in case the configuration was not changed during the last 6 hours (or more) then it is safe to proceed.

At the boot stage the Endian UTM Appliance looks for a specific label in the SD card partition table. If there is no match, the SD card will be initialized, setting up newly formatted partitions and creating the required files and folders.

In order to let the Endian UTM Appliance initialize again the SD card you just have to remove the partition table. Every tool that does this job works fine, the two most common ways being:

  1. Using the Endian UTM Appliance itself

  2. Using a different PC capable of reading the SD card

Due to the process of SD card re-initialization, the first boot with a reset card may require 4-5 minutes before completion.

Delete the partition table from Endian CLI

You can perform this operation from the web console as well via SSH, but the recommended option to follow safely the process is via serial console.

The dd command sets to "zero" the first part of the physical device where the partition table is stored:

root@endian:~ # dd if=/dev/zero of=/dev/mmcblk0 bs=512 count=1

If you prefer to completely wipe the SD card you can just run dd command without bs and count options: The whole device's sectors will be set to zero, until you get a warning telling you that there is no space left on device.

root@endian:~ # dd if=/dev/zero of=/dev/mmcblk0
dd: writing `/dev/mmcblk0': No space left on device
7744513+0 records in
7744512+0 records out
3965190144 bytes (4.0 GB) copied, 958.519 seconds, 4.1 MB/s

When the SD card will be plugged in again, your Endian UTM Appliance will detect it and trigger its actions (format the card and set it up) accordingly.


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