On Wed, 2018-11-21 at 14:10 +0100, Fabian Groffen wrote: > 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.
I'm wondering about that as well, yes. However, my main idea is to specifically detect 'gpkg:' there and use it to explicitly identify the file as Gentoo binary package (and print package name). > > > 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. > I think the modern GNU tar format is the obvious choice here. I think it doesn't suffer any portability problems these days, and is more compact than the PAX format. -- Best regards, Michał Górny
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