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On Wed, 2018-11-21 at 14:10 +0100, Fabian Groffen wrote: |
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> On 20-11-2018 21:33:17 +0100, Michał Górny wrote: |
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> > The volume label |
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> > ---------------- |
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> > |
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> > The volume label provides an easy way for users to identify the binary |
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> > package without dedicated tooling or specific format knowledge. |
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> > |
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> > The implementations should include a volume label consisting of fixed |
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> > string ``gpkg:``, followed by a single space, followed by full package |
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> > identifier. However, the implementations must not rely on the volume |
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> > label being present or attempt to parse its value when it is. |
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> > |
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> > Furthermore, since the volume label is included in the .tar archive |
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> > as the first member, it provides a magic string at a fixed location |
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> > that can be used by tools such as file(1) to easily distinguish Gentoo |
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> > binary packages from regular .tar archives. |
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> |
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> Just for clarity on this point. |
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> Are you proposing that we patch file(1) to print the Volume Header here? |
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> file-5.35 seems to not say much but "tar archive" or "POSIX tar archive" |
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> for tar-files containing a Volume Header as shown by tar -tv. |
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I'm wondering about that as well, yes. However, my main idea is to |
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specifically detect 'gpkg:' there and use it to explicitly identify |
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the file as Gentoo binary package (and print package name). |
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> |
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> > Container and archive formats |
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> > ----------------------------- |
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> > |
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> > During the debate, the actual archive formats to use were considered. |
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> > The .tar format seemed an obvious choice for the image archive since |
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> > it is the only widely deployed archive format that stores all kinds |
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> > of file metadata on POSIX systems. However, multiple options for |
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> > the outer format has been debated. |
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> |
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> You mention POSIX, which triggered me. I think it would be good to |
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> specify which tar format to use. |
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> |
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> POSIX.1-2001/pax format doesn't have a 100/256 char filename length |
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> restriction, which is good but it is not (yet) used by default by GNU |
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> tar. busybox tar can read pax tars, it seems. |
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> |
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I think the modern GNU tar format is the obvious choice here. I think |
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it doesn't suffer any portability problems these days, and is more |
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compact than the PAX format. |
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-- |
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Best regards, |
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Michał Górny |
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