Re: When is /etc/fstab called?

[Joseph A Knapka <jknapka@earthlink.net>]

Allen Curtis wrote:
>>>I was wondering if someone could clarify this behavior.
>>>
>>>Recently I created a custom kernel which calls a custom "init"
>>
>>script. While
>>
>>>debugging the "strange" behavior I discovered that Linux processed
>>>/etc/fstab and mounted the root file-system specified before "init" was
>>>called. This was unfortunate since I was trying to reformat the
>>
>>device that
>>
>>>was now mysteriously mounted.
>>
>>Well, consider that the kernel has to be able to *find* /etc/fstab
>>in the first place, which means the filesystem containing /etc
>>must be mounted for the kernel to fully boot.
> 
> 
> Perhaps I need to be a little clearer. The boot parameters specified
> root=/dev/ram0. (which is what rdev does without a recompile) As you
> mentioned this indicates that the kernel knew what root was and therefore
> could read /etc/fstab. The /etc/fstab specified a different device as being
> root but I didn't expect it to be mounted before init was called. I wanted
> to work with the device, unmounted first. Although mount reported the new
> device as root I don't believe that it is the "real" root. No pivot_root or
> chroot was performed. I believe that the device was unformatted at one time
> and therefore must have been still using the ram disk image. So for the most
> part this was an annoyance and an unexpected problem to solve.

Ah. Much clearer, and I don't know why you'd see this behavior :-(
I guess there's some code in the kernel that pivots the root to
whatever is specified in /etc/fstab on the rdev'd root? I've
just grepped the 2.4.18 tree and didn't find any likely-looking
culprit, though...

-- Joe


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