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Old 07-17-2012, 12:49 PM   #16
jbennett
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I have never seen a 'boot:' prompt. It comes up with various options for booting

Verify and boot
Boot
Boot (Text Mode)
Boot (Basic Video)
Install
Install (Text Mode)
Memory Test
Boot from local drive

I can select an option and hit tab to edit options. So let's say I select boot and hit tab:

I get the following:

Code:
vmlinuz0 initrd=initrd0.img root=live:CDLABEL=CentOS-6.2-i386-LiveDVD rootfs type=auto ro liveimg quiet nodiskmount nolvmount rhgb vga=791 rd.luks=0 rd.md=0 rd.dm=0
I have tried to enter linux rescue at the end of all of this, but it just takes me to the desktop GUI for the LiveDVD.
 
Old 07-17-2012, 06:24 PM   #17
michaelk
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The DVD1 installation disk has a "Rescue installed system" menu item. This is the rescue option.
 
Old 07-17-2012, 07:01 PM   #18
whizzit
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Having downloaded and taken a look at the 6.2 LiveCD (x86_64) I can find no evidence of the traditional rescue mode. I double checked my Red Hat 6 installation DVD and this has the rescue mode.

Initial conclusions are that the LiveCD/DVDs don't have the rescue function.
 
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Old 07-17-2012, 07:17 PM   #19
michaelk
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True, and since it is a liveCD it shouldn't need a rescue mode. I assumed the OP was referring to the intallation DVD vs liveCD.
 
Old 07-17-2012, 07:22 PM   #20
whizzit
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Looking back on this thread I can confirm you have all the information to able to continue to the next stage of attempting to fix the password/login issue; and possibly beyond.

Tip: chroot(1) is going to be a friend here. (howtos are in links in posts in the thread but man(1) also has value)

Logs can be very useful so be sure to check out /var/log/ for signs of trouble.
 
Old 07-17-2012, 07:38 PM   #21
whizzit
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@michaelk: The benefit of the installation CD rescue mode is that it makes life a little bit easier setting up the chroot. Ultimately, yes, either can be used

Last edited by whizzit; 07-17-2012 at 07:40 PM. Reason: Clarify last sentence
 
Old 07-18-2012, 03:25 PM   #22
jbennett
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I have managed to get into rescue mode with a CentOS 5 DVD that I found. I realize most people would just pop in a DVD and make one on their computer, but they have removed all burners from our computers and I'm still waiting on one to come from our HelpDesk.

Upon the system trying to mount my OS under /mnt/sysimage, I get the following:

Code:
An error occurred trying to mount some or all of your system.  Some of it may be mounted under /mnt/sysimage.
Once I'm in shell, I see the following: /mnt/sysimage/proc & /mnt/sysimage/sys

I can go to /dev and I see /dev/VolGroup00/LogVol00 & /dev/VolGroup00/LogVol01

Here's where I'm confused. I'm under the impression that the file system is already mounted (the Rescue DVD automated this process, correct?). Earlier, it was suggested that I '# mount /dev/VolGroup00/LogVol00 /mnt/sysimage'. However, wasn't this done automatically? Or would it not have mounted the Logical Volume and instead have mounted something else?

If LogVol00 is already mounted, my next step should be as follows:

# mount -t proc none /mnt/sysimage/proc
# mount -o bind /dev /mnt/sysimage/dev

Or was this already done as well by booting into rescue?

If these first few steps are already completed automatically, then I suppose I move onto chrooting? (these steps?)

Thanks again for all of the assistance. I've learned a tremendous amount in the last week!
 
Old 07-19-2012, 09:52 AM   #23
whizzit
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Quote:
Originally Posted by jbennett View Post
Upon the system trying to mount my OS under /mnt/sysimage, I get the following:

Code:
An error occurred trying to mount some or all of your system.  Some of it may be mounted under /mnt/sysimage.
Once I'm in shell, I see the following: /mnt/sysimage/proc & /mnt/sysimage/sys

I can go to /dev and I see /dev/VolGroup00/LogVol00 & /dev/VolGroup00/LogVol01

Here's where I'm confused. I'm under the impression that the file system is already mounted (the Rescue DVD automated this process, correct?). Earlier, it was suggested that I '# mount /dev/VolGroup00/LogVol00 /mnt/sysimage'. However, wasn't this done automatically? Or would it not have mounted the Logical Volume and instead have mounted something else?
It depends on which options you chose when booting into the rescue environment. For example, it is optional to have the rescue CD/DVD search for your installation and mount the appropriate volumes under /mnt/sysimage. It sounds like this is what you've selected, correct me if I am wrong, based on the error above.

Quote:
Originally Posted by jbennett View Post
Or was this already done as well by booting into rescue?
Yes, if you selected the option to search for installations and automatically mount it. Execute mount to see what's mounted

Quote:
Originally Posted by jbennett View Post
If these first few steps are already completed automatically, then I suppose I move onto chrooting? (these steps?)
I would advise sticking with CentOS or Red Hat documentation in this instance. All the information you need for now is in
this thread's post #10. Other distros' docs are likely to confuse.

If you selected the default options, as I have done in this test, then you should end up with a final and informative screen output as depicted in the screenshot ( it's Red Hat but should be virtually identical to CentOS ).

After a chroot(1) you will effectively be in your 'broken' system as if you had logged into it. Most tools hereon should work as they normally would in the running system.

Regards
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Old 07-23-2012, 02:34 PM   #24
jbennett
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I did not get the same window. Instead, I have the following notice:

Code:
An error occurred trying to mount some or all of your system.  Some of it may be mounted under /mnt/sysimage.
I can move on and I am at the sh-3.2# prompt and I have the following when I try to chroot:

Code:
sh-3.2# chroot /mnt/sysimage
chroot: cannot run command '/bin/sh' : No such file or directory
 
Old 07-23-2012, 05:47 PM   #25
whizzit
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Hi there,

That wasn't expected. But you haven't told me anything other than it didn't work
  • Was there anything interesting in the logs? ( perhaps via dmesg or /var/log/messages and so on )
  • One of the other TTYs has output e.g. second/third? ( you can switch between them using Alt-F2, Alt-F3 etc. ).
  • What happens when you try to mount the root volume manually with mount? ( likely to be another error message ).
  • What is mounted?
  • If your root volume cannot be mounted, try a fsck against it and attempt a remount or reboot into rescue mode to try again.

Can you refresh my memory on what volumes there are by running lvs -a please?

Thanks!

Last edited by whizzit; 07-23-2012 at 05:58 PM. Reason: correct grammar
 
  


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