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Old 03-07-2008, 04:58 PM   #1
thatwaschrislee
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dmesg not complete


Hello,
I have recently been experimenting building my own kernel and have run into some trouble. I feel my first problem is reading the messages outputted during boot-up.

Why are some lines displayed during boot-up but are omitted in /var/log/dmesg?

During boot-up, I can see something about VFS:... and then many hundred lines quickly scroll by looking similar to the following:
udev[349]: delete_path: rmdir(/dev/.udev/failed) failed: Read-only file system

When I check dmesg, there is no mention of any of the above errors.

chris
 
Old 03-07-2008, 05:26 PM   #2
Brian1
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I don't know why log does differ than what is on the screen but if you wish to review you can try this. I don't know the distro or version you have but here is an example of a Redhat distro to review what is on the screen.

When the grub boot manager comes up hit the 'e' key then if it is a default grub then you move up or down with the arrow key to highlight the kernel you boot. Usually defaults it. Then hit ' e ' again and you have the boot kernel configuration. arrow down to the vmlinuz line and hit ' e' again. Arrow to the end of the line and if there is the words like rghb and quiet remove those and add the number ' 3 ' to it. Hit ' b ' to boot the kernel into runlevel 3. Once booted you are at a login prompt. Hold down the left shift key and then hit page up key to scroll back. Should see everything that went to the screen from start to finish.

Brian
 
Old 03-07-2008, 11:31 PM   #3
thatwaschrislee
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I am using slackware 12.0, linux kernel 2.6.24.3.

After boot-up I can use right-shift+pgup to see some of the boot messages but since there are so many of the mentioned udev lines, the buffer fills up and I cannot see what happens at the beginning.

chris
 
Old 03-08-2008, 08:49 AM   #4
Brian1
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No ideas as to the cause. Might google for like a portion of the error and get an idea to the cause.

Brian
 
Old 03-08-2008, 10:52 AM   #5
H_TeXMeX_H
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Try checking '/var/log/syslog' and '/var/log/messages'. Those two combined should have everything output to the screen and more.
 
Old 03-08-2008, 02:06 PM   #6
thatwaschrislee
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Quote:
Originally Posted by H_TeXMeX_H View Post
Try checking '/var/log/syslog' and '/var/log/messages'. Those two combined should have everything output to the screen and more.
I've checked these two files but there is no mention of the udev errors I am receiving.

btw, there may be a bunch of errors with a cp operation just before the mentioned udev problems. It flashes too quickly to be sure though.

Any other ideas??

chris
 
Old 03-08-2008, 02:42 PM   #7
pwc101
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Try hitting the pause/break key on your keyboard during the boot process - it should pause the output as it's going by, so you can make a note of it.

To resume the boot process, press pause/break again, or hit enter.

See http://en.wikipedia.org/wiki/Break_key for more info (apparently, Ctrl+NumLock has the same effect).
 
Old 03-08-2008, 02:47 PM   #8
thatwaschrislee
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Quote:
Originally Posted by pwc101 View Post
Try hitting the pause/break key on your keyboard during the boot process - it should pause the output as it's going by, so you can make a note of it.
...(apparently, Ctrl+NumLock has the same effect).
I tried both and neither paused the output. I also tried some combinations of CTRL+pause, ALT+pause... nothing. Am I missing something??

chris
 
Old 03-08-2008, 02:53 PM   #9
pwc101
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No, I don't think so. It works for me, if I remember rightly. Sorry :/
 
Old 03-08-2008, 04:52 PM   #10
thatwaschrislee
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I guess what I am looking for is where do I find udevmonitor's output. This is not in /var/log/syslog or /var/log/messages no matter what udev_log level is set to.

Anybody know?

thanks for the help so far,
chris
 
Old 03-08-2008, 06:00 PM   #11
thatwaschrislee
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maybe a bit elementary, but I've found the scroll lock key to pause the start-up. Not much immediate need for the log anymore...

thanks for the suggestions,

chris
 
Old 03-08-2008, 06:58 PM   #12
Tinkster
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Quote:
Why are some lines displayed during boot-up but are omitted in /var/log/dmesg?
As for dmesg not matching what you see on screen: that's because
dmesg is a window into the kernel ring-buffer. Problems
with scripts are NOT on kernel level, hence won't show there.



Cheers,
Tink

Last edited by Tinkster; 03-08-2008 at 07:02 PM.
 
  


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