[Buildroot] [PATCH] Makefile: Update mtime of $(TARGET_DIR)/usr

[Yann E. MORIN <yann.morin.1998@free.fr>]

Chris, All,

On 2018-04-24 13:56 -0500, Chris Lesiak spake thusly:
> >     date    what
> >     0       build version 1
> >     1       version is flahes onto a device, boxed and shipped
> >     2       build version 2
> >     3       the device with version 1 is received, unboxed and booted
> >     4       that device downloads version 2 and updates to it
> >
> >As you can see, the /etc/.updated and/or /var/.updated will dated '3'
> >but the mtime of /usr version 2 will be 2 (because touched at build
> >time).
> 
> Not quite.
> 
> If systemd-update-done if working correctly, then on date 3, /etc/.updated
> and /var/.updated will get created with mtime 0, not mtime 3.? Then on date
> 4, /etc/.updated and /var/.updated will get updated (because 0 is less than
> 2) to mtime 2.
> 
> When /etc/.updated and /var/.updated are originally created and then again
> when they are updated, their mtime will match the mtime of /usr, not the
> current time when systemd-update-done runs.

OK, makes sense. Thanks for the clraification.

So, this touch is eventually mostly usefull for a read-only rootfs, in
fact (for a read-only rootfs, the touch could be done by the update
mechanis).

Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

Regards,
Yann E. MORIN.

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