AV Linux Basic Booting Bible

[GMaq]

Hi,

The Linux Kernel is a marvel of hardware support and detection but as it becomes more sophisticated and open-source Video drivers continue to evolve occasionally booting a Live system requires some troubleshooting or extra Kernel commands to boot successfully. This guide is mostly geared towards LiveDVD disk media.

When booting an AV Linux ISO:

1. Be patient...it can take several seconds to start the boot especially on LiveDVD media.

2. Watch for disk activity, if you see nothing immediately on the monitor but there is disk activity it is still working on the boot.

3. Closely observe the Kernel console text output for red text errors, warnings and even many regular console colored errors are normally harmless. The reason AV Linux doesn't use a pretty bootsplash is so the user can monitor what the Kernel is doing at boot.

4. If the console output completes and the GDM login window appears wait for it to auto-login which will take several seconds on the LiveDVD and may not appear at all when booting from a Unetbootin USB Key.

5. If the desktop partially loads OR the display resolution is wrong or corrupted it is most likely a Kernel Modesetting/Video Driver issue which is covered in detail below.


Failure to boot can be caused by several issues:

1. A corrupted or broken ISO image on the Project ftp server.

This is extremely unlikely and rare and is easily ruled out by a single successful install by an end-user, AV Linux is pre-tested by a third party before any release is made public to make sure the ftp ISO images are intact and functional.

2. A bad download of the ISO image.

This is not common, but quite possible and can be verified by using the accompanying ISO.md5 file from the ftp download folder. Another simple indication is if the file sizes on both the ftp and the downloaded file match perfectly.

3. A bad burn of the ISO to disk media

This is usually the most likely cause of boot failure and is generally evident when the disk does nothing at all or freezes after displaying a few lines of console text which may be accompanied by numerous console red error messages. Always burn any compressed filesystem media like ISO images at low burn speeds (i.e. 4X or less) and make sure to use good disk media. If a LiveDVD fails try it on a different computer, this is the number one way to discern if your media is bad or not or whether your computer has a specific hardware issue with the LiveDVD.

4. Incompatible Video Hardware and Kernel Mode Setting (KMS)

This is a recent issue and has been exacerbated by Kernel inclusion of more specialized open-source Video drivers for both ATi and nVidia cards. Issues result when the Kernel supports Kernel Mode Setting and the Xorg driver is faulty or the Video hardware does not work with Mode Setting. This issue is generally evidenced by the Kernel completing it's console output and dying at the GDM login or unsuccessfully trying to load the Desktop and/or displaying the Desktop at a very low or garbled resolution.


Booting Command Cheatcodes:

AV Linux LiveDVD's use ISOlinux as a bootloader and this allows for some extra Kernel boot commands to be applied at boot, A complete novel could be written about the literal hundreds of possible boot cheatcodes but this guide with focus on Mode Setting since it is by far the most common issue. If you have a nVidia or ATi Radeon HD Video card and experience the Mode Setting issues above you can supply a 'nomodeset' cheatcode to the Kernel at boot time. Two examples will be provided for both LiveDVD and Unetbootin USB Keys.


FIXING KMS RELATED LIVE BOOT PROBLEMS

LiveDVD:

Booting into the LiveDVD will begin with the ISOlinux screen shown below, If you want to add the 'nomodeset' boot parameter then hit the 'Tab' key on your keyboard before ISOlinux automatically boots the default 'live' option, you will be greeted by an option like this:

Code:

boot:
  live xforcevesa textonly memtest hd
boot:  

at this point type and enter:

Code:

live nomodeset

nVidia users can try this if the above isn't successful:

Code:

live nomodeset xdrvr=nv

ATi users can try this if the above isn't successful:

Code:

live radeon.modeset=0

Unetbootin USB Key:

Unetbootin USB Keys use Syslinux as a bootloader and require modification of the 'syslinux.cfg' text file found on your USB Key that was created with Unetbootin. Mount your key in the file manager and find the syslinux.cfg file and right click on it and open it with the 'gedit' text editor found in the 'Accessories' menu.

Change the Kernel boot commands by adding 'nomodeset' like in the example below, in this example this has been modified on both the 'Default' boot option and the 'Live' boot option. ATi users should replace 'nomodeset' with 'radeon.modeset=0'



Of course other boot issues are possible and are extremely frustrating to troubleshoot for both the end user and the distributor, this guide is suggested reading as a first line of assistance for those having difficulty with the AV Linux LiveDVD/USB.

Below is a further exhaustive list of ISOlinux cheatcodes:
http://www.remastersys.com/forums/index.php?topic=70.0