Logging the boot process

Booting the Asus T100 into Ubuntu Linux takes forever – but why? To find out, we need to show the commands being executed as they occur and/or to review the commands used at the end of the boot process.

To view the boot commands as they occur, we can edit the initial boot command sequence. At the grub menu, press “E” (for edit) on the keyboard. Use the arrow keys to locate and delete the text “quiet” (so as to allow the commands to be displayed as they occur), “splash” (disabling the display of the Ubuntu-logo screen, and “vt.handoff=7” (avoiding the display of an initial blank, purple screen). A whole raft of commands will now roll by as the machine goes through the boot process.

Once the machine has booted into Ubuntu Linux, to see the entire boot sequence, navigate to File System/var/log and open the file syslog in the text editor.

When viewing the syslog file, my problem with disk access errors when trying to boot the Asus T100 was quite apparent due to the large number of repetitions of the following sequence of commands/errors:

Aug 24 13:42:46 Asus-T100TA kernel: [ 517.841049] end_request: I/O error, dev mmcblk0rpmb, sector 128
Aug 24 13:42:46 Asus-T100TA kernel: [ 517.844809] Buffer I/O error on device mmcblk0rpmb, logical block 16
Aug 24 13:42:54 Asus-T100TA kernel: [ 526.053415] mmc0: Got data interrupt 0x00000002 even though no data operation was in progress.
Aug 24 13:42:54 Asus-T100TA kernel: [ 526.058826] mmcblk0rpmb: error -110 transferring data, sector 16, nr 8, cmd response 0x900, card status 0xb00
Aug 24 13:42:54 Asus-T100TA kernel: [ 526.061891] mmcblk0rpmb: retrying using single block read
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.063938] mmcblk0rpmb: timed out sending r/w cmd command, card status 0x400900
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.069109] mmcblk0rpmb: timed out sending r/w cmd command, card status 0x400900
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.074296] mmcblk0rpmb: timed out sending r/w cmd command, card status 0x400900
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.079461] mmcblk0rpmb: timed out sending r/w cmd command, card status 0x400900
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.084546] mmcblk0rpmb: timed out sending r/w cmd command, card status 0x400900
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.089568] mmcblk0rpmb: timed out sending r/w cmd command, card status 0x400900
Aug 24 13:42:55 Asus-T100TA kernel: [ 526.092419] end_request: I/O error, dev mmcblk0rpmb, sector 16

The problem evidently relates to mmcblk0rpmb, which is the eMMC SSD hard drive in the T100. Now, the question is how to fix all those timeout errors!

References:

DebuggingKernelBoot
https://wiki.ubuntu.com/DebuggingKernelBoot

Does Ubuntu log events occurring during the boot?
http://askubuntu.com/questions/145553/does-ubuntu-log-events-occurring-during-the-boot

What is eMMC
http://www.datalight.com/solutions/technologies/emmc/what-is-emmc

Purpose of MMCBLK0* files?
http://www.linuxquestions.org/questions/linux-mobile-81/purpose-of-mmcblk0*-files-881207/

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