tree 86e554a0e34d2cdc083589bfd6b678253bbad1b1
parent 41d2d2675d2092d906d185488e77fadd247f1672
author Jan Kundrát <jan.kundrat@cesnet.cz> 1509383147 +0100
committer Jan Kundrát <jan.kundrat@cesnet.cz> 1509383147 +0100

RAUC: Copy old /cfg to the new /cfg during updates

It seems that RAUC doesn't really have a concept of hooks that are
already located on the system being updated. One could completely
replace some steps, but that's not what I want to do because I do not
really want to duplicate the logic for rootfs.

Instead, let's go with hooks stored in the individual bundles. In the
end, I do not think that this is a huge drawback -- the updates will
have to contain this hook "somewhere", either in the rootfs, or in the
bundle metadata. Having it just in the bundle metadata is no worse. In
fact, it's better because changes take effect immediately.

How this works:

- an empty tarball is needed because RAUC otherwise attempts to mmap() a
directory when no image file name is given
- because there's an empty tarball, the cfg FS gets wiped at first
- this empty tarball is then extracted over the just-made FS
- finally, our hooks runs and copies stuff from the existing /cfg into
the new /cfg

This all means that any configuration changed after this update won't
survive a reboot into the new software. This should probably be
documented somewhere.

Change-Id: I12b11ab93f53f99f1d8875655fa9ec9575830586