[pbs-devel] [RFC proxmox-backup 0/3] Encode creation parameters into pxar archive

[Gabriel Goller]

Thanks for the review!

On Wed Mar 6, 2024 at 4:13 PM CET, Christian Ebner wrote:
> Wouldn't it make sense to extend the pxar file format by a dedicated
> entry type to store such information? And handle these entries in a
> dedicated manner? E.g. by a `PXAR_CLI_PARAMS` entry header?

I though about this but disregarded it ultimately because of the whole 
version update and backwards compat hassle. IMO this is 'debug data' 
and 'extra information' so it would fit better inside the archive (same
as the exclude-patterns, these are also not really important after the 
archive has been created (except for debugging)). If for some reason 
this data is missing it wouldn't be a problem at all.

> While this approach has already been used up until now for storing the
> pxar cli exclude patterns, allowing to encode such metadata inside the
> archive as regular file without having any means other than the filename
> to find and distinguish this information from other files seems not
> ideal to me.

We could also specify some kind of prefix for pxar-specific files,
something like '.pxar_***'? This way we stay consistent and users can
distinguish manually encoded files from their files.
But I also get your point about having regular files appear in the pxar
archive could be confusing to some. And obviously having 3+ of these
files is a no-go.

> This would of course require an updated pxar format version 2, which we
> might need anyways if the patches regarding metadata based change
> detection should be applied.

Although this is a good point, if we merge both series in the same
window, we would only have to do one update! 


For some reason—now that I am writing this obviously—I am currently more
inclined to your version. Mostly because the `.pxarexclude` file also
allows input (e.g. the user can create the file insert stuff), while 
the `.pxar_creation_params` does not allow input and would have to 
overwrite/ignore an existing file.

I am open to other suggestions/inputs!