missing shared library in ldd

Question

I compiled Apache httpd on CentOS 6.x. Works fine there.

Then I moved the binary files to CentOS 7. I needed to install some missing libraries and now works fine there.

Then I moved the binary files to Archlinux. As I expected it did not started directly:

httpd: symbol lookup error: /software_pack/httpd-2.2.25/lib/libapr-1.so.0: undefined symbol: dlopen

However, if I do ldd /software_pack/httpd-2.2.25/lib/libapr-1.so.0 it gives different results on CentOS and Archlinux. On Archlinux, libdl.so is not shown at all?

Where from CentOS knows the file needs libdl.so.2 ?

CentOS 6.x:

# ls -la /software_pack/httpd-2.2.25/lib/libaprutil-1.so.0
lrwxrwxrwx 1 root root 21 Jul 30 09:47 /software_pack/httpd-2.2.25/lib/libaprutil-1.so.0 -> libaprutil-1.so.0.5.2
# ldd /software_pack/httpd-2.2.25/lib/libaprutil-1.so.0.5.2
        linux-vdso.so.1 =>  (0x00007fffec400000)
        libexpat.so.0 => /software_pack/httpd-2.2.25/lib/libexpat.so.0 (0x00007f5ec94d8000)
        libapr-1.so.0 => /software_pack/httpd-2.2.25/lib/libapr-1.so.0 (0x00007f5ec92a8000)
        librt.so.1 => /lib64/librt.so.1 (0x00007f5ec9098000)
        libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007f5ec8e60000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f5ec8c40000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f5ec88a8000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f5ec9928000)
        libfreebl3.so => /lib64/libfreebl3.so (0x00007f5ec8630000)
        libdl.so.2 => /lib64/libdl.so.2 (0x00007f5ec8428000)   <<<<<<<< Missing in arch

On Archlinux:

# ls -la /software_pack/httpd-2.2.25/lib/libaprutil-1.so.0
lrwxrwxrwx 1 root root 21 Jul 30 10:47 /software_pack/httpd-2.2.25/lib/libaprutil-1.so.0 -> libaprutil-1.so.0.5.2
# ldd /software_pack/httpd-2.2.25/lib/libaprutil-1.so.0.5.2
        linux-vdso.so.1 (0x00007fff7cdd3000)
        libexpat.so.0 => /software_pack/httpd-2.2.25/lib/libexpat.so.0 (0x00007f5aef4e7000)
        libapr-1.so.0 => /software_pack/httpd-2.2.25/lib/libapr-1.so.0 (0x00007f5aef2ba000)
        librt.so.1 => /usr/lib/librt.so.1 (0x00007f5aef084000)
        libcrypt.so.1 => /usr/lib/libcrypt.so.1 (0x00007f5aeee4b000)
        libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f5aeec2d000)
        libc.so.6 => /usr/lib/libc.so.6 (0x00007f5aee87f000)
        /usr/lib64/ld-linux-x86-64.so.2 (0x00007f5aef934000)

Does `libapr-1.so.0` link to `libapr-1.so.0.4.8`? It looks like you are running `ldd` on different files. — grekasius, Jul 30 '14 at 14:15
yes "bundled" apr, located in apache's lib directory (same file) — Nick, Jul 30 '14 at 14:16
For consistency, update the output so that it shows exactly same file on both systems. — grekasius, Jul 30 '14 at 14:18

score 3 · Accepted Answer · edited May 23 '17 at 11:33

3

dlopen is normally provided by libdl.so.2. On Arch Linux libdl.so.2 is provided by glibc package. It would be very strange if you didn't have glibc installed, but anyway, check if you have libdl.so.2 on your system.

You can also use readelf command to output a symbol table for a shared object and check if particular symbol is exported:

readelf -Ws /usr/lib/libdl.so.2

Some info on why ldd output for the same binary may differ on different systems can be found here:

https://stackoverflow.com/questions/12714219/ldd-different-output-same-binary-different-distros

edited May 23 '17 at 11:33

Community

1

answered Jul 30 '14 at 14:34

grekasius

2,046
11
15

I am marking your answer as correct. The real way I fixed the thing was to delete all libapr-1 files from apache bundled directory (e.g. /software_pack/httpd-2.2.25/lib/ ). This made linker to link with "real" apr files from /lib64 directory. – Nick Jul 30 '14 at 16:32
May I ask why you deploy it this way? Is it a customized apache build? – grekasius Jul 30 '14 at 16:53
I made this build for my CentOS servers, but I want to be able to run it on my Archlinux too. It is full "stack" - nginx, apache, php5.2, pho5.4, mariadb, redis. – Nick Jul 31 '14 at 07:00

missing shared library in ldd

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