Ubuntu – Ubuntu freezes during boot


I'm running ubuntu 14.04 on a Acer E17 laptop. From one to another the computer seems to freeze during the boot sequence. It boots to grub without an issue, but when I select Ubuntu it seems to freeze on a black screen. No indication as to what it's doing or any error code. Normally it would display the word Ubuntu with 5 dots beneath it that change from white to red.

If I boot the recovery boot (of the same kernel) and in recovery immediately hit resume it boots normally and I can login.

I already tried to downgrade some recent updates using synaptic, but that did not help. The next thing I tried is to try to create some boot logs with bootlogd, but /var/log/boot.log remains empty. Does anyone have an idea where to go next?

Edit: after a couple of days /var/log/boot.log and /var/log/boot have some information, but no errors of any kind.

cat /var/log/boot produces this output: http://pastebin.com/FEjBveEG

cat /var/log/boot.log produces this output: http://pastebin.com/iycLg0p0
(formatting is off, no idea why, it isn't in the output)

Best Answer

Ubuntu actually waits for all the essential drivers and environment application to load before log you in. In my case, I intended to overwrite the default (lightdm unity) with gnome-shell, bit it failed and the boot sequence was waiting infinitely for it to run. So I need to rollback my changes but there isn't much i can do since I cant actually get myself to terminal (the "shift" + boot didn't work).

Here's what I did to resolve the issue:

  1. Plugged in my usb bootable ubuntu and ran trial version.
  2. Browsed through the bootdrive and edited /etc/X11/default-display-manager.
  3. It didn't allow me to write so I assigned writable permission to it with sudo chmod 777 /etc/X11/ -R.
  4. Then I changed the line /usr/sbin/gdm to /usr/sbin/lightdm and the rebooted. By doing this I rolled back the changed from gnome-shell to lightdm, and I saved myself from reinstalling the system.
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