Re: [gentoo-dev] [pre-GLEP r2] Gentoo binary package container format

[Fabian Groffen]

On 20-11-2018 21:33:17 +0100, Michał Górny wrote:
> The volume label
> ----------------
>
> The volume label provides an easy way for users to identify the binary
> package without dedicated tooling or specific format knowledge.
>
> The implementations should include a volume label consisting of fixed
> string ``gpkg:``, followed by a single space, followed by full package
> identifier.  However, the implementations must not rely on the volume
> label being present or attempt to parse its value when it is.
>
> Furthermore, since the volume label is included in the .tar archive
> as the first member, it provides a magic string at a fixed location
> that can be used by tools such as file(1) to easily distinguish Gentoo
> binary packages from regular .tar archives.

Just for clarity on this point.
Are you proposing that we patch file(1) to print the Volume Header here?
file-5.35 seems to not say much but "tar archive" or "POSIX tar archive"
for tar-files containing a Volume Header as shown by tar -tv.

> Container and archive formats
> -----------------------------
>
> During the debate, the actual archive formats to use were considered.
> The .tar format seemed an obvious choice for the image archive since
> it is the only widely deployed archive format that stores all kinds
> of file metadata on POSIX systems.  However, multiple options for
> the outer format has been debated.

You mention POSIX, which triggered me.  I think it would be good to
specify which tar format to use.

POSIX.1-2001/pax format doesn't have a 100/256 char filename length
restriction, which is good but it is not (yet) used by default by GNU
tar.  busybox tar can read pax tars, it seems.

Thanks,
Fabian

-- 
Fabian Groffen
Gentoo on a different level