How to implement and check a rpm for an 'rpmlib' capability

[Thierry Parmentelat]

Hi

I'm facing issues with rpm in a rather convoluted scenario, where a fedora14 physical box spins off virtual machines, and in the mix invokes rpm/yum to build guest images

Long story short, for guests under fedora 17 and 18, I run into this 
ERROR You need to update rpm to handle:
rpmlib(X-CheckUnifiedSystemdir) is needed by filesystem-3.1-2.fc18.x86_64
rpmlib(X-CheckUnifiedSystemdir) is needed by setup-2.8.57-1.fc18.noarch

As far as I understand fedora has added this as a precaution for upgrades across the f16/f17 barrier and I really do not plan on doing any of this, so using an rpm binary/package that fakes this 'X-CheckUnifiedSystemdir' thing would be enough for my needs at first sight

Trying to work around that, I made an attempt to rebuild f18's rpm under f14; which was easy enough; at first sight it seemed to have the proper f18 patch so I was optimistic :)

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Unfortunately using this new rpm did not solve the issue, and when trying to check that the new rpm indeed had the required capability - or whatever the proper name is here, I mean 'X-CheckUnifiedSystemdir' - I realized that even with the native f18 rpm I was not able to spot that feature:

# rpm -qp rpm-4.10.2-1.fc18.x86_64.rpm --provides
warning: rpm-4.10.2-1.fc18.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID de7f38bd: NOKEY
config(rpm) = 4.10.2-1.fc18
rpm = 4.10.2-1.fc18
rpm(x86-64) = 4.10.2-1.fc18


mmh, my first thought had been this would show up in there, but obviously, it's not, even with the stock f18 rpm 
so digging further I found references here and there to --showrc; I',m not sure that I captured that one, but here's what I get

root at mirror /mirror/fedora/updates/18/x86_64 # rpm -qp rpm-4.10.2-1.fc18.x86_64.rpm --showrc | grep rpmlib
Features supported by rpmlib:
   rpmlib(BuiltinLuaScripts) = 4.2.2-1
   rpmlib(CompressedFileNames) = 3.0.4-1
   rpmlib(ConcurrentAccess) = 4.1-1
   rpmlib(ExplicitPackageProvide) = 4.0-1
   rpmlib(FileCaps) = 4.6.1-1
   rpmlib(FileDigests) = 4.6.0-1
   rpmlib(HeaderLoadSortsTags) = 4.0.1-1
   rpmlib(PartialHardlinkSets) = 4.0.4-1
   rpmlib(PayloadFilesHavePrefix) = 4.0-1
   rpmlib(PayloadIsBzip2) = 3.0.5-1
   rpmlib(PayloadIsLzma) = 4.4.2-1
   rpmlib(PayloadIsXz) = 5.2-1
   rpmlib(ScriptletInterpreterArgs) = 4.0.3-1
   rpmlib(VersionedDependencies) = 3.0.3-1

which already looks better indeed; except that it does not mention X-CheckUnifiedSystemdir...

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I am quite obviously missing the point here
All I would like to achieve is to build an rpm that pretends to have the required feature - without any actual change, can anybody shed some light on how to do that ?

Many thanks in advance