This has affected one of my 14.04 web servers and a couple of 12.04, out of 40 Ubuntu servers.
All show the following in the Apache error log:
[Thu May 26 02:29:08.076578 2016] [mpm_prefork:notice] [pid 2199] AH00171: Graceful restart requested, doing restart
apache2: Syntax error on line 191 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/php5.load: Cannot load /usr/lib/apache2/modules/libphp5.so into server: /lib/x86_64-linux-gnu/libm.so.6: symbol __strtold_nan, version GLIBC_PRIVATE not defined in file libc.so.6 with link time reference
This has affected one of my 14.04 web servers and a couple of 12.04, out of 40 Ubuntu servers.
All show the following in the Apache error log: notice] [pid 2199] AH00171: Graceful restart requested, doing restart apache2. conf: Syntax error on line 1 of /etc/apache2/ mods-enabled/ php5.load: Cannot load /usr/lib/ apache2/ modules/ libphp5. so into server: /lib/x86_ 64-linux- gnu/libm. so.6: symbol __strtold_nan, version GLIBC_PRIVATE not defined in file libc.so.6 with link time reference
[Thu May 26 02:29:08.076578 2016] [mpm_prefork:
apache2: Syntax error on line 191 of /etc/apache2/
Manually restarting Apache fixed the problem.