Hi the list, Here is the error result for nagios compilation. I don't know why this compilation failed. I've upgraded my OS, and perl was also upgraded (5.8.3 -> 5.8.7). Have you encountered this problem and how have you resolved it ? Thanks in advance for replies Best regards make nagios cd ./base && make make[1]: Entering directory `/usr/local/src/nagios-2.5/base' gcc -g -O2 -DPERL_DISABLE_PMC -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm -I/usr/lib/perl5/5.8.7/i386-linux/CORE -DHAVE_CONFIG_H -DNSCORE -c -o perlxsi.o perlxsi.c gcc -g -O2 -DPERL_DISABLE_PMC -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm -I/usr/lib/perl5/5.8.7/i386-linux/CORE -DHAVE_CONFIG_H -DNSCORE -o nagios nagios.c broker.o nebmods.o checks.o config.o commands.o events.o flapping.o logging.o notifications.o sehandlers.o utils.o retention-base.o xretention-base.o comments-base.o xcomments-base.o objects-base.o xobjects-base.o statusdata-base.o xstatusdata-base.o perfdata-base.o xperfdata-base.o downtime-base.o xdowntime-base.o perlxsi.o -Wl,-export-dynamic -Wl,-E -Wl,-rpath,/usr/lib/perl5/5.8.7/i386-linux/CORE -L/usr/local/lib /usr/lib/perl5/5.8.7/i386-linux/auto/DynaLoader/DynaLoader.a -L/usr/lib/perl5/5.8.7/i386-linux/CORE -lperl -lnsl -ldl -lm -lcrypt -lutil -lc -lm -lpthread -lltdl checks.o: In function `run_service_check': /usr/local/src/nagios-2.5/base/checks.c:123: undefined reference to `PL_thr_key' utils.o: In function `my_system': /usr/local/src/nagios-2.5/base/utils.c:2585: undefined reference to `PL_thr_key' utils.o: In function `deinit_embedded_perl': /usr/local/src/nagios-2.5/base/utils.c:4602: undefined reference to `PL_op_mutex' /usr/local/src/nagios-2.5/base/utils.c:4606: undefined reference to `Perl_croak_nocontext' collect2: ld returned 1 exit status make[1]: *** [nagios] Erreur 1 make[1]: Leaving directory `/usr/local/src/nagios-2.5/base' make: *** [nagios] Erreur 2