How to add shared library search path to a executable file?

I build the ffmpeg with librtmp. My librtmp is at /opt/librtmp/lib. When I execute the ffmpeg, it said:

./ffmpeg: error while loading shared libraries: librtmp.so.0: cannot open shared object file: No such file or directory

I use ldd command it displays not found:

[qty@testing bin]# ldd ffmpeg 
        linux-vdso.so.1 =>  (0x00007fff15576000)
        librtmp.so.0 => not found
        libz.so.1 => /lib64/libz.so.1 (0x00002b9a71e10000)
        libm.so.6 => /lib64/libm.so.6 (0x00002b9a72025000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b9a722a8000)
        libc.so.6 => /lib64/libc.so.6 (0x00002b9a724c3000)
        /lib64/ld-linux-x86-64.so.2 (0x00002b9a71bf2000)

I know my so at:

[qty@testing bin]# ls -alh  /opt/librtmp/lib/
total 300K
drwxr-xr-x 3 root root 4.0K Sep 25 17:10 .
drwxr-xr-x 7 root root 4.0K Sep 25 17:10 ..
-rw-r--r-- 1 root root 158K Sep 25 17:10 librtmp.a
lrwxrwxrwx 1 root root   12 Sep 25 17:10 librtmp.so -> librtmp.so.0
-rwxr-xr-x 1 root root 118K Sep 25 17:10 librtmp.so.0
drwxr-xr-x 2 root root 4.0K Sep 25 17:10 pkgconfig

I found several ways to fix the problem

modify /etc/ld.so.conf, but it required a supper user
set LD_LIBRARY_PATH variable, but it is not conventient to users
pass rpath to gcc, like this

configure args for my ffmpeg

PKG_CONFIG_PATH="/opt/librtmp/lib/pkgconfig" ./configure --disable-doc \
--disable-ffserver --disable-avdevice \
--disable-postproc --disable-avfilter --disable-bsfs \
--disable-filters \
--disable-asm \
--disable-bzlib \
--enable-librtmp \
--prefix=/opt/ffmpeg \
--extra-ldflags="-Wl,-rpath,/opt/librtmp/lib"

Assume there are no source code to re-compile? How do add the shared library search path to a executable file ?

Solution

You could use addrpath to add an RPATH to your elf file.

The RPATH will work like LD_LIBRARY_PATH, that is, telling the dynamic loader to search for the shared libraries in that path. RPATH will be permanently in your ELF file.