root@nsa310:~# uname -a
Linux nsa310 [COLOR="rgb(46, 139, 87)"]2.6.31.8[/COLOR] #2 Fri Aug 2 11:21:44 CST 2013 armv5tel GNU/Linux

I have a Zyxel NSA310 with a factory-installed apache:

root@nsa310:~# /usr/sbin/httpd -V
Server version: Apache/2.2.9 (Unix)
Server built: Jan 17 2013 15:28:39
Server's Module Magic Number: 20051115:15
Server loaded: APR 1.3.0, APR-Util 1.3.0
Compiled using: APR 1.3.0, APR-Util 1.3.0
Architecture: 32-bit
Server MPM: Prefork
threaded: no
forked: yes (variable process count)
Server compiled with....
-D APACHE_MPM_DIR="server/mpm/prefork"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_SYSVSEM_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=128
-D HTTPD_ROOT="/usr/local/apache2"
-D SUEXEC_BIN="/usr/local/apache2/bin/suexec"
-D DEFAULT_PIDLOG="logs/httpd.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_LOCKFILE="logs/accept.lock"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="conf/mime.types"
-D SERVER_CONFIG_FILE="conf/httpd.conf"

It doesn't contain the mod_proxy_ajp.so module so I downloaded Apache/2.2.9 sources and compiled them with same compiler options in order to obtain mod_proxy_ajp.so module. When I'm loading the module with:
LoadModule proxy_ajp_module /usr/local/zy-pkgs/lib/mod_proxy_ajp.so
at starting I'm getting the error:
root@nsa310:~/apache2/bin# /bin/nice -n -2 /usr/sbin/httpd -f /etc/service_conf/httpd.conf
httpd: Syntax error on line 16 of /etc/service_conf/httpd.conf: Cannot load /usr/local/zy-pkgs/ffproot/ffp/home/root/apache2/modules/mod_proxy_ajp.so into server: libc.so.0: cannot open shared object file: No such file or directory

The compiled version outputs same result for httpd -V and it starts fine with de same module loading declaration. What the error means ?

Can you post output of
ldd /usr/sbin/httpd
ldd /usr/local/zy-pkgs/ffproot/ffp/home/root/apache2/modules/mod_proxy_ajp.so

There is probably some naming convention clash with your libc.so file.

I think libc.so.0 is an uClibc file only.

You could try : # ln -s libc-<version>.so libc.so.0

( Like this glibc example : # ln -s libc-2.16.so libc.so.0 )

-

Thank you for your help; I try:
root@nsa310:~# ldd /ffp/lib/mod_proxy_ajp-2.2.9.so
ldd: can't open cache '/ffp/etc/ld.so.cache'
checking sub-depends for '/ffp/lib/libpthread.so.0'

• ld-uClibc.so.0 => /ffp/lib/ld-uClibc.so.0 (0x2a000000)
• libdl.so.0 => /ffp/lib/libdl.so.0 (0x4001d000)
• libc.so.0 => /ffp/lib/libc.so.0 (0x40028000)

checking sub-depends for '/ffp/lib/libc.so.0'

• ld-uClibc.so.0 => /ffp/lib/ld-uClibc.so.0 (0x2a000000)
• libpthread.so.0 => /ffp/lib/libpthread.so.0 (0x00000000)
• libc.so.0 => /ffp/lib/libc.so.0 (0x00000000)
• /ffp/lib/ld-uClibc.so.0 => /ffp/lib/ld-uClibc.so.0 (0x00000000)

then I found all files