I read up on "prelink" as suggested; and used "ldd /sbin/mkfs.ext3" to see what the dependencies (libraries) are.
There are 13 dependencies; file size is the same between servers but md5sum's are different!
Most of these libraries have other libraries they call; I finally drilled down to ld-2.5.so which is statically built.
Same thing: same file size, same datestamp, same package version; but the binary is actually different; yet rpm -V does not complain. Why?
(Both systems are running CentOS 5.4; one was deployed in December 2009, the other in April 2010.)
[root@server1 /lib64]# ls -l ld-2.5.so -rwxr-xr-x 1 root root 139416 Sep 2 2009 ld-2.5.so [root@server1 /lib64]# md5sum ld-2.5.so ad38c69452b3990852c0d3e0ea51a31b ld-2.5.so [root@server1 /lib64]# ldd ld-2.5.so statically linked [root@server1 /lib64]# rpm -q -f /lib64/ld-2.5.so glibc-2.5-42 [root@server1 /lib64]# rpm -V glibc [root@server1 /lib64]#
[root@server2 /lib64]# ls -l ld-2.5.so -rwxr-xr-x 1 root root 139416 Sep 2 2009 ld-2.5.so [root@server2 /lib64]# md5sum ld-2.5.so ddb5ad336c3cf40ee2c69b91ef7bfd04 ld-2.5.so [root@server2 /lib64]# ldd ld-2.5.so statically linked [root@server2 /lib64]# [root@server2 /lib64]# rpm -q -f /lib64/ld-2.5.so glibc-2.5-42 [root@server2 /lib64]# rpm -V glibc-2.5-42 [root@server2 /lib64]#