That error means the runtime link loader (ld.so) has failed to find the definition of a symbol. In other words, you're probably missing a shared library in the runtime link loader's shared library search path.

One of three things have happened.

(1) You built the program from source yourself and have not installed it or a dependency library, so the library is not found in the default shared library search path.

(2) You have installed a prebuilt binary without using your OS's installation procedures and have not installed required runtime dependencies, so the libraries are not available.

(3) The developer made an error.

You can determine what libraries are missing by using the ldd command on the jack binary to list how the runtime link loader will resolve the libraries.

You can resolve the first two problems by either using your OS's software installation tools, finding building and installing the required libraries, or setting the environment variable LD_LIBRARY_PATH as appropriate. The exact resolution depends on what has caused the error.

That sounds like a missing lib. Try uninstalling and reinstalling.

A name like "jackd" sounds like a daemon, a program not normally run from the command line. It could very well be that the normal way of running the daemon requires the setting of LD_LIBRARY_PATH before the daemon gets lunches so that libraries in a nonstandard directory get picked up.

Find out how the daemon is supposed to be launched (eg. from an init.d script), and check to see if the LD_LIBRARY_PATH environment variable gets set first.

The qjack tool can be used to start the jack daemon, setting any relevant environment variables for you and passing settings flags. It might make things simpler.