Cannot boot laptop due to video driver

[Robin Laing]

On 2015-01-16 00:55, poma wrote:
> On 16.01.2015 07:20, Robin Laing wrote:
>> Hello,
>>
>> I am trying to help my child whom is across the country repair their
>> laptop after installing the wrong video driver.  They can boot into
>> emergency mode but not any of the other kernels.
>>
>> During booting into the system, the boot process stops close to the
>> point of starting KDM.
>
>
> It is *boot*-ing OK, only the *init*-ialization of the userspace service - in your case display/login manager(KDM), doesn't work.
> KDM depends on the X server, which in turn depends on functional X video module *and* kernel video module.
> You should deal with modules within 'multi-user.target'. i.e. non-graphical user environment and shouldn't touch the configuration of the boot loader, at all.
>


It was the wee hours of the morning for my child and I am not that 
familiar with the new systemd commands and couldn't figure out how to 
get into a single or multi-user with no X.  The boot process didn't 
leave things at a terminal window or allow ctrl+alt+F{x} to work. 
Basically it was reboot to do anything.

Emergency mode didn't work as per the documentation with chroot and 
being so late, it was easier to take sometime to read up on it.  The 
laptop wasn't needed until Saturday.

Some searching later and found that I was close last night, just didn't 
know the correct services command to run.

I think this would be beneficial in the Fedora documentation and I am 
willing to write it for addition.

What we ended up doing.

1.  On boot, we paused grub and in the edit mode added "single" to the 
end of the "vmlinuz" line.
	linux    /vmlinuz-3.17.7-300 ... single

2.  Once booted into emergency mode, entered the root password.

3.  Started Network Manager with
	systemctl start NetworkManager.service

This started the network but it wasn't working wireless or wired.  The 
only wired connection was for a different network with a static IP and 
different gateway IP.

4.  Listed the connections
	nmcli  connection show

5.  Created a new network connection with
	nmcli connection edit con-name <name of new connection>
where the ethernet port was used and ipv4 selected.  Saved on quit.

6.  Restarted Network Manager (not sure if this step was needed or not)
	systemctl  restart NetworkManager.service

7.  On restart, Network Manager selected the wrong connection again. 
Started the correct one.
	nmcli  connection down id <wrong connection name>
	nmcli connection up id <new connection name>

8.  Tested network connections to see if DHCP had worked and it did.  We 
used ping tests to 8.8.8.8 (Google public name server) and ping 
Google.ca for a DNS test.

9.  Use RPM to find the problem driver.
	rpm -qa | grep nvidia

10. Used yum to erase the problem driver
	yum erase <problem driver>

11. Rebooted
	shutdown -r now

And all is well on the reboot.

I have to find time to learn systemd better.

Hope this helps someone else.

Robin