I am trying to install CentOS-6 on an eMMC drive. Since the supported 2.6.xx kernel from CentOS-6 doesn't support mmc, I compiled a newer kernel (4.2.6) which has updated mmc drivers. I tried booting using this kernel, but I still don't see /dev/mmcblk0.

When the boot exits to a shell without finding /dev/mmcblk0, I see that mmc_core, mmc_block and sdhci_acpi modules are loaded. Does anyone know how to make this available during boot ?

The same procedure works fine with the FC22/23 which has a 4.2.x kernel. What am I missing here ? Thanks for any hint.

*** EDIT

Here is the dmesg output. http://pastebin.com/STq4LuwK

*** Correction

mmc_block module is NOT loaded. Only mmc_core and sdhci-acpi and sdhci

*** EDIT-1

Changing udev rules inside initrd image, I could load mmc_block, but that still doesn't solve the problem.

  • First of all: please attach a dmesg output – silvio Dec 24 '15 at 23:58
  • definitely, by Tuesday... no access to machine... happy holidays... – iamauser Dec 25 '15 at 0:09
  • @silvio dmesg output is added along with a correction... – iamauser Dec 28 '15 at 17:21
  • 1
    So, a kernel from Centos works, but your custom kernel did not ? Then you did not build the modules needed for your hard drive. See also google.com/… – Panther Dec 30 '15 at 22:50
  • @bodhi.zazen CentOS kernel-2.6.xxx does not work. Only FC22 onwards work. I am compiling latest mmc drivers with the same CONFIG_MMC_* as the FC22/23. That doesn't help. I must be missing some other module that is not obvious... – iamauser Dec 30 '15 at 23:22
  1. Different kernels might not use the same names for block devices. It is preferred that you add a label to your block device and look for it /dev/disk/by-label.

  2. If you suspect that some module, enabled in Fedora kernels, is missing from your kernel configuration, you can get Fedora's kernel configuration and start from there:

    zcat /proc/config.gz > config


As it turned out, for my particular system, a kernel config was missing. It was the LPSS support from Intel. CONFIG_X86_INTEL_LPSS which has the particular support for 80860F14 acpi peripheral and needed for my Samsung eMMC drive. After including this, mmc block and core drivers could see /dev/mmcblk0.

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