Cannot boot laptop due to video driver

[poma]

On 17.01.2015 05:51, Robin Laing wrote:
> 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
> 

Before you begin to test a new video modules, it is recommended to do this:
# systemctl set-default multi-user.target

Switching from multi-user.target i.e. non-graphical user environment
to graphical.target i.e. graphical user environment
is done as follows:
# systemctl isolate graphical.target

After confirming the new configuration, you can return to graphical user environment:
# systemctl set-default graphical.target


In this way, complicated procedure you mentioned is unnecessary.