SOLVED: unable to launch app due to "cannot open shared object file"

[Matthew Saltzman]

On Sat, 19 May 2007, Tony Nelson wrote:
>>>>>
>>>> Well, everyone was helpful.  Turned out that when I ran "echo
>>>> LD_LIBRARY_PATH" it was empty.  I added /usr/local/lib by typing (I
>>>> think):  ]$ LD_LIBRARY_PATH=/usr/local/lib and then:
>>>> export LD_LIBRARY_PATH
>>>>
>>>> That should do it, at least until I have to shut down and boot up
>>>> again.  :)
>>>> Tom
>>>>
>>>
>>> Google on "linux library search path" to find out why LD_LIBRARY_PATH isn't
>>> such a good idea.
>>>
>> I'm afraid to look.  :)
>> What's a better alternative?
>
> AIUI, either putting the lib in a standard location (/usr/lib) or adding a
> file to /etc/ld.so.conf.d/ and then running ldconfig (man ldconfig).  The
> suggestion was that LD_LIBRARY_PATH affects all uses of shared libs and
> that can have unintended consequences.  Perhaps /usr/local/lib is safe
> enough.

A normal user can't install a shared-lib package for his own use in, say, 
~/lib this way because (1) he needs root to update the ld.so database and 
(2) even if he could update the ld.so database, it would then include a 
path inaccessible to other users.  Also, you don't want net-mounted 
filesystems in the ld.so path because if they are unavailable, nothing can 
load.

The other alternative is to build the paths to shared libs into the binary 
itself at link time.  The problem with that is that the libs then have to 
be installed in the specified locations (again probably requiring root and 
possibly violating installation standards) or the user has to build the 
binary himself with the lib locations specified.  The latter is the best 
alternative, as long as the source is available and the user is 
experienced enough to build it.

If a normal user gets a package prebuilt with shared libs, he's kind of 
stuck.  In this case, the best bet is probably a wrapper script that sets 
LD_LIBRARY_PATH only for the environment in which the particular binary is 
run.

See, e.g,, http://www.eyrie.org/~eagle/notes/rpath.html.

-- 
 		Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs