Você pode fazer o yum info para ver, do yum instalado por exemplo.
Considere o zlib em uma caixa Centos 6 -
yum info zlib
Installed Packages
Name : zlib
Arch : i686
Version : 1.2.3
Release : 29.el6
Size : 136 k
Repo : installed
From repo : base
Summary : The zlib compression and decompression library
URL : http://www.gzip.org/zlib/
License : zlib and Boost
Description : Zlib is a general-purpose, patent-free, lossless data compression
: library which is used by many different programs.
Name : zlib
Arch : x86_64
Version : 1.2.3
Release : 29.el6
Size : 149 k
Repo : installed
From repo : anaconda-CentOS-201311272149.x86_64
Summary : The zlib compression and decompression library
URL : http://www.gzip.org/zlib/
License : zlib and Boost
Description : Zlib is a general-purpose, patent-free, lossless data compression
: library which is used by many different programs.
Ele mostra From Repo para você.