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I think the reason for this is that yumdb is including default and mandatory packages from when you install a group. Some people have written in to say the command shows packages that they never explicitly installed, things like ModemManager and firware packages.
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Yumdb search reason dep |egrep "agg|boost-iostreams|boost-serialization|gtkglext-libs|pangox-compat" List packages which were installed as deps:
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If you’re after a way to list all the packages you have explicitly installed (rather than packages that have been pulled in as a dependency) then you can do that with yumdb (thanks to Panu on #yum for the tip) which is powered by a new database added in 2009.
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