Ubuntu Debugging

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Revision as of 15:19, 3 August 2010 by Michael Opdenacker (Talk | contribs)
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Boot Ubuntu without the graphical interface

It could be useful to boot our standard OMAP releases Ubuntu without the graphical environment, for example when you have an experimental kernel which limited graphics support, or when you just need to ssh on your system for native compiling (in which case the graphics would waste RAM and CPU).

To do this, you just need to add a parameter to the kernel bootargs. In the U-boot command line, just type:

setenv bootargs ${bootargs} text
boot

Of course, you could add saveenv to make this change permanent.

What's nice about this technique is that it doesn't require any change in the root filesystem.

Boot Ubuntu desktop / netbook on NFS

At least if you boot your root filesystem directly (without going through a standard Ubuntu initramfs), you probably noticed:

The system hangs during the boot sequence. It's because of NetworkManager that reinitializes the network interface that you used for NFS.

A quick workaround is just to disable NetworkManager, for example by renaming the corresponding upstart configuration file:

sudo mv /etc/init/network-manager.conf /etc/init/network-manager.conf.disabled

Of course, this is shouldn't be done in a user environment, because users will need NetworkManager (to connect to their wired and wireless networks). However, this can make your life easier if you are involved in product test or development.

Debug the userspace init sequence

To trace the sequence of processes and events during the init sequence, you can run init in debug mode by adding init=/sbin/init --debug to the kernel command line. In the U-boot shell, for example:

setenv bootargs ${bootargs} init=/sbin/init --debug

This shows debug information in the system console.

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