SL 6.1 (and I assume RHEL and CentOS 6.1 as well) has introduced an issue for building and running FreeSWITCH. Apparently a lot of stuff now relies on dynamically linking to libnss3. libnss3, in turn, depends on libnspr4.so, which depends on libplds4.so. Seemingly, this should not be an issue (stuff depends on chained shared objects all over the place), but somehow it is.

What happens is first you can't compile FreeSWITCH. You get complaints about unresolved symbols in /usr/lib64/libnss3.so. The solution is to run the following commands:

yum install nspr-devel
env LIBS="-lnss3 -lnspr4 -lplds4" ./configure
make && make install

This will get you a compiled version of FreeSWITCH. However, when you actually run it, you'll find that several modules won't load at runtime (including the ODBC driver, should you happen to be using it). The solution for this is similar. Assuming you are using an init script to launch FreeSWITCH, you can add the following line to the top of /etc/init.d/freeswitch:

export LD_PRELOAD="/usr/lib64/libnss3.so /usr/lib64/libnspr4.so /usr/lib64/libplds4.so"

Voila. Everything works. Hopefully the FreeSWITCH devs get on RHEL6 support soon, but meanwhile this should get you by.