ext4 - getting at birth time (file create time) and getting/setting nanosecond time stamps and utime

[jim owens]

Andreas Dilger wrote:
> On 19-Oct-09, at 16:24, Steve French wrote:
>> On Mon, Oct 19, 2009 at 3:11 PM, Andreas Dilger <adilger at sun.com> wrote:
>>> As for being able to write to the "create time" attribute, I would 
>>> prefer
>>> that this be a filesystem mount option.  For some users (myself 
>>> included)
>>> I don't care whether Windows is unhappy that it can't update this 
>>> creation
>>> time - I'd prefer to know when a file is actually created.
>>
>> I agree - if create time could be overwritten - that behavior hould be
>> configurable (another post mentioned the alternative to mount
>> option - a flag for this perhaps along the lines of the a "backup intent"
>> flag - although somewhat different than what Windows uses that for).
> 
> If this is a flag that a user can configure/select themselves, then it
> is completely useless to me.  If it is a mount option and/or possibly an
> additional process capability that would be more useful.

Restricting the modification of create time is pointless.

A number of filesystems and operating systems besides windows
have create time and it MUST be settable on restore just like
the access and modification times.

There is no value in it needing "special privileges".  What
you are forgetting is *NO* timestamp on a filesystem can be
trusted to be correct.  All times are just fields set based
on what the system thinks the time is now (not to mention that
any disk editor can change the field).  The "now time" can be
intentionally or accidentally set wrong, or as has happened to
me, a totally crap value from a bad RTC battery. :)

I did legal records storage a long time ago, and I can
guarantee you disk timestamps are meaningless.

On the other hand, if you just want stamps for debugging
and internal purposes, then you do what I did, put versions
and times inside on-disk metadata structures the filesystem
does not expose.  As long as you remember all stamps are still
at the mercy of those who can patch your clock, your code,
and your raw disk blocks.

jim