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Old 02-24-2009, 07:43 PM   #1
Registered: May 2008
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Booting into a read-only drive


I have a custom Linux installation that resides in a NAND flash chip that acts as the root drive. It boots up fine when the drive is read/write. However when I jumper the drive to read-only, which is its final state, it fails to load.

I'm using kernel and LILO boot loader. In lilo.conf I have already included "read-only".

The file system seems to already be in read only mode since I'm unable to create files once I'm booted up w/o the jumper. I don't understand why then does it not boot when I jumper it to read only? When I do this, once the kernel decompresses I get nothing, no debug messages even. It just hangs there.


Last edited by galapogos; 02-24-2009 at 08:18 PM.
Old 02-26-2009, 05:28 AM   #2
Registered: Aug 2005
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Distribution: Redhat FC4, Fedora 8 and AIX 5.3, AIX 6.1
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I will try to see if my logic may make sense here but when you say that you have your root drive as read only I could see how you may be getting the problems that your are getting. What I mean by that is if I am looking at this correct your root drive will consist of /, /var, /etc, /home, /tmp, /opt, /root and maybe others don't know what all you may have created in the form of filesystems on it. This will have to be a writeable drive since at the time of boot your hardware is walked and things get stored in /dev with new timestamps and if you can't write to the drive I can see several things failing. Even things in /var and /tmp could be created for temp files and jobs so I really don't see how the drive if it is a true root drive in what I am thinking of root as in all of the base default dirs which the system must have to be able to run. Hope that helps I just don't see how linux or any unix will work in a read only mode for the root of the OS when it creates and writes new data to files but at the same time I really don't know what all you have done in your custom Linux install don't know if was written to not do what a normal linux install does.
Old 02-26-2009, 06:08 AM   #3
Registered: May 2008
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Thanks. My kernel booting up doesn't write to the drive. My "init" is simply a busybox shell. I've actually found the problem to be pertaining to LILO, and I've fixed it. Thanks again!
Old 02-26-2009, 10:20 AM   #4
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Just for the sake of completeness:
Could please post what the exact problem was with the LILO settings and how you'd fixed it?


Last edited by gergely89; 02-27-2009 at 11:03 PM.
Old 02-26-2009, 07:39 PM   #5
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Sorry, forgot to include that.

Well, you know LILO's "BIOS data check successful" message? Apparently after that, it writes some status messages to the drive. Since my drive is write-protected, it hangs there. After I include "suppress-boot-time-BIOS-data" in lilo.conf, it bypasses the check and hence works.
Old 03-01-2009, 07:47 AM   #6
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I'm curious --

How are you solving the /dev /var /tmp writability issue raised by shadow5277?
What is actually on the NAND flash chip & what is linked elsewhere?
Linked to where?
With what mechanism, i.e. are you using Aufs or UnionFS, or possibly something else?


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