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HELP! Linux won't start

Posted on 2006-06-05
Medium Priority
Last Modified: 2012-06-27
My linux box has refused to start up all day...The last lines that are showing on the screen are:
Switching to new root
SELinux: Disabled at runtime
SELinux: Unregistering netfileter hooks
INIT: version 2.85 booting
uname uses obsolete (PF_INET,SOCK_PACKET)
ACPI: PCI interrupt 0000:02:05.0[A] -> GSI 5 (level, low) -> IRQ 5
ACPI: PCI interrupt 0000:02:05.0[A] -> GSI 5 (level, low) -> IRQ 5
eth0: 3Com Gigabit LOM (3C940)
        PrefPort:A    RlmtMode: Check Link State
device eth0 entered promiscuous mode

That's it---
Its Asterisk@Home Box running CentOS-- newest updates via yum
Question by:moruda
LVL 22

Expert Comment

ID: 16831998
This could be all sorts of things causing the problem...but of course you have a backup?

Unfortunately, although this is probably repairable, it is not for the faint hearted if you end up having to rebuild your grub setup or initrds.

First of all, we need to get a lot more information from you!

You need to understand the grub boot process a bit more:


and also try ctrl-alt-f1,f2,f3,f4 when it freezes. This will give you error outputs and also various other messages that may be helpful. If you post the results of this, then I can probably provide further direction.

You may wish to download knoppix, and use that to examine file systems or repair the system later, once we know what the problem is:


LVL 22

Expert Comment

ID: 16832008
Newest updates via yum - have these 'just' been installed? In which case, do you know what was installed that might be causing the problems.

Another thing to try is can you boot in 'single' mode? At the 'grub' screen, edit the config for the boot, and add 'single' to the end of the root line.

LVL 11

Expert Comment

ID: 16832029
> SELinux: Disabled at runtime
> SELinux: Unregistering netfileter hooks
Are you using the whole time SELinux or this is a new improvement to your system security?
If you have newly installed SELinux then perhaps this is the reason for why your system is not booting up;
SELinux is still e quite new Project in a beta stage,so using it still is very experimental and only for really good security geeks;
perhaps this manual ,will give you some light:
it's regarding SELinux on RHEL 4 ,but as your running CentOS there should be no difference,or just in very particular cases.
Just explain us :when and how did you install SELinux nad are aware of it's hardening system....

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Author Comment

ID: 16833010
The machine does not work even in single mode- I tried it at least 4 times. When it freezes, the keyboard is frozen too--even numlock and capslock don't work -- I doubt that ctrl-alt-f1... will work, but will try it out. Everything was working fine and over the weekend something changed. Maybe someone hacked the machine--my password is really good, but who knows. I have no idea what happened. I just know that I didn't do it. If SELinux is not good, how do I get rid of it?

In my opinion, it seems like whatever is happening after that Eth0 is initialized is what is causing it to hang.
LVL 31

Expert Comment

ID: 16833136
Can you remove the NIC (Eth0)? Seems it hangs after making the NIC enter promiscuous mode (have you requested that?) so a hardware change just may have some impact.

Author Comment

ID: 16833186
i can't remove the nic (on mb) but I disabled it from bios and it still happens. i can boot up with a slax cd to access the files, how do i see what is trying to run, so I can disable it? maybe its acpi for all i know
LVL 16

Accepted Solution

xDamox earned 2000 total points
ID: 16833209

SELinux is good it makes your machine more secure. The first step I would recommend doing is place your CentOS CD into the
cdrom and boot into rescue mode this means at the boot prompt type:

linux rescue

Once you are in the linux rescue enviroment you will need to chroot into your system this is explain when the rescue is under way. Once inside your chrooted rescue envrioment try this:

/sbin/grub-install /dev/hda

This will reinstall grub for you and may help with the error.  Also while your in your rescue enviroment you might want to build your initial ramdisk image you can do this by using the following command:

/sbin/mkinitrd /boot/initrd-2.2.5-15.img 2.2.5-15

Next edit your /boot/grub/menu.lst to use your new initial ramdisk image.

Note also in your rescue envrioment you may be able to backup files.

Expert Comment

ID: 16862699
try adding init=/bin/sh to your boot options, that will get you a shell, if nothing else.

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