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Re: /boot partition changes when it should not



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>> ro	Mount filesystem read only. Note that ext3 will replay
>> 	the journal (and thus write to the partition) even when
>> 	mounted "read only". Mount options "ro,noload" can be
>> 	used to prevent writes to the filesystem.

Great! Spectacular find! I didn't know this.

>> There is really no need for a journal on /boot.  Why not use ext2?

Up to now, I never heard of any advantage whatsoever of ext2 over ext3.

Stephen Powell wrote:
> The most likely causes are a "dirty shutdown" 

Definitely not the case here.

> or alterations made by the boot loader.  

That's what I suspect.

> For example, the boot loader may be updating the mount
> count or updating the "last referenced date/time", if there is such
> a field in the filesystem, for the kernel image or the initial RAM
> disk image.

I assume you mean "atime", which exists in ext3. And no, it was not
updated. I checked with ls, it has the same value it had since the last
kernel update.

> Many filesystems have a "last referenced date/time"
> field for a file, which gets updated even if the file itself is accessed
> read-only.  

Yes, so does ext3. No, it did not update the atime record of anything in
/boot.

> If the filesystem is
> mounted read-only, then this field may not be maintained. 

For ext3, "ro" implies "noatime", and I put "noatime" in fstab anyway.

> But the
> boot loader doesn't know that Linux is going to mount the filesystem
> read-only. 

That's a highly interesting point. It doesn't? I thought everything in
the boot process mounts everything it finds read-only until when the
kernel is running. Even the kernel at some point during boot says it now
remounts the / filesystem read-write, hence even that must have been
read-only until then.

> And it may be maintaining that field when it reads
> the kernel image or the initial RAM disk image.

As I said, nothing in the filesystem metadata got updated.


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