How can same httpd file have different library dependencies? (libexpat.so.0) - linux

Question

It started with httpd not starting on one of my machines:
$ /usr/sbin/httpd -v
/usr/sbin/httpd: error while loading shared libraries: libexpat.so.0: cannot open shared object file: No such file or directory
There are two machines of almost identical configuration. Centos 6.6 32-bit. Both httpd binaries have an identical size and identical md5 sum.
However, the library dependencies are different. I thought those dependencies are embedded into the binary at link time. So how can the dependencies be different?
Below note the broken httpd has two extra dependencies, libexpat.so.0 (not found) and librt.so.1.
Working httpd
# ldd /usr/sbin/httpd
linux-gate.so.1 => (0xb773b000)
libm.so.6 => /lib/libm.so.6 (0xb769c000)
libpcre.so.0 => /lib/libpcre.so.0 (0xb766c000)
libselinux.so.1 => /lib/libselinux.so.1 (0xb764d000)
libaprutil-1.so.0 => /usr/lib/libaprutil-1.so.0 (0xb762a000)
libcrypt.so.1 => /lib/libcrypt.so.1 (0xb75f9000)
libexpat.so.1 => /lib/libexpat.so.1 (0xb75d1000)
libdb-4.7.so => /lib/libdb-4.7.so (0xb745b000)
libapr-1.so.0 => /usr/lib/libapr-1.so.0 (0xb742d000)
libpthread.so.0 => /lib/libpthread.so.0 (0xb7412000)
libc.so.6 => /lib/libc.so.6 (0xb727b000)
/lib/ld-linux.so.2 (0x49e18000)
libdl.so.2 => /lib/libdl.so.2 (0xb7275000)
libuuid.so.1 => /lib/libuuid.so.1 (0xb7270000)
libfreebl3.so => /lib/libfreebl3.so (0xb726c000)
Broken httpd
$ ldd /usr/sbin/httpd
linux-gate.so.1 => (0xb7721000)
libm.so.6 => /lib/libm.so.6 (0xb7686000)
libpcre.so.0 => /lib/libpcre.so.0 (0xb7656000)
libselinux.so.1 => /lib/libselinux.so.1 (0xb7637000)
libaprutil-1.so.0 => /usr/lib/libaprutil-1.so.0 (0xb761d000)
libcrypt.so.1 => /lib/libcrypt.so.1 (0xb75ec000)
libexpat.so.1 => /lib/libexpat.so.1 (0xb75c4000)
libdb-4.7.so => /lib/libdb-4.7.so (0xb744e000)
libapr-1.so.0 => /usr/lib/libapr-1.so.0 (0xb7429000)
libpthread.so.0 => /lib/libpthread.so.0 (0xb740e000)
libc.so.6 => /lib/libc.so.6 (0xb7277000)
/lib/ld-linux.so.2 (0x00871000)
libdl.so.2 => /lib/libdl.so.2 (0xb7271000)
libexpat.so.0 => not found
libuuid.so.1 => /lib/libuuid.so.1 (0xb726c000)
librt.so.1 => /lib/librt.so.1 (0xb7263000)
libfreebl3.so => /lib/libfreebl3.so (0xb725f000)

Answer 1

If the binaries are identical, but ldd shows different dependencies, it must have something to do with the earlier dependencies requiring different libraries. Indeed, the output shows that the size of the libraries different between systems. Maybe you could make the system libraries identical by updating one or both systems?
– wallyk
I copied all the referenced libs from a different machine and now it works. – Danny