Apache Common Problems and
Question: Why won't
Apache compile with my system's cc?
Answer: If the server won't
compile on your system, it is probably due to one of the
The Configure script doesn't recognize your system environment.
This might be either because it's completely
unknown or because the specific environment (include files, OS
version, et cetera) isn't explicitly handled. If this happens,
you may need to port the server to your OS yourself.
Your system's C compiler is garbage.
Some operating systems include a default C
compiler that is either not ANSI C-compliant or suffers from
other deficiencies. The usual recommendation in cases like this
is to acquire, install, and use gcc.
Your include files may be confused.
In some cases, we have found that a compiler
installation or system upgrade has left the C header files in an
inconsistent state. Make sure that your include directory tree
is in sync with the compiler and the operating system.
Your operating system or compiler may be out
Software vendors (including those that develop
operating systems) issue new releases for a reason; sometimes to
add functionality, but more often to fix bugs that have been
discovered. Try upgrading your compiler and/or your operating
Question: Why do I get complaints about
redefinition of "struct iovec" when compiling under Linux?
Answer: This is a conflict
between your C library includes and your kernel includes. You
need to make sure that the versions of both are matched
properly. There are two workarounds, either one will solve the
Remove the definition of struct iovec from your C library
includes. It is located in /usr/include/sys/uio.h. Or,
Add -DNO_WRITEV to the EXTRA_CFLAGS line in your Configuration
and reconfigure/rebuild. This hurts performance and should only
be used as a last resort.
Question: I'm using gcc and I get some
compilation errors, what is wrong?
Answer: GCC parses your
system header files and produces a modified subset which it uses
for compiling. This behaviour ties GCC tightly to the version of
your operating system. So, for example, if you were running IRIX
5.3 when you built GCC and then upgrade to IRIX 6.2 later, you
will have to rebuild GCC. Similarly for Solaris 2.4, 2.5, or
2.5.1 when you upgrade to 2.6. Sometimes you can type "gcc -v"
and it will tell you the version of the operating system it was
If you fail to do this, then it is very likely that Apache will
fail to build. One of the most common errors is with readv,
writev, or uio.h. This is not a bug with Apache. You will need
to re-install GCC.
Question: Why do I get "setgid: Invalid
argument" at startup?
Answer: Your Group directive
(probably in conf/httpd.conf) needs to name a group that
actually exists in the /etc/group file (or your system's
equivalent). This problem is also frequently seen when a
negative number is used in the Group directive (e.g., "Group
#-1"). Using a group name -- not group number -- found in your
system's group database should solve this problem in all cases.
Question: Why am I getting "httpd:
could not set socket option TCP_NODELAY" in my error log?
Answer: This message almost
always indicates that the client disconnected before Apache
reached the point of calling setsockopt() for the connection. It
shouldn't occur for more than about 1% of the requests your
server handles, and it's advisory only in any case.
Question: Why am I getting "connection
reset by peer" in my error log?
Answer: This is a normal
message and nothing about which to be alarmed. It simply means
that the client canceled the connection before it had been
completely set up - such as by the end-user pressing the "Stop"
button. People's patience being what it is, sites with
response-time problems or slow network links may experiences
this more than high-capacity ones or those with large pipes to
Question: The errorlog says Apache
dumped core, but where's the dump file?
Answer: In Apache version
1.2, the error log message about dumped core includes the
directory where the dump file should be located. However, many
Unixes do not allow a process that has called setuid() to dump
core for security reasons; the typical Apache setup has the
server started as root to bind to port 80, after which it
changes UIDs to a non-privileged user to serve requests.
Dealing with this is extremely operating system-specific, and
may require rebuilding your system kernel. Consult your
operating system documentation or vendor for more information
about whether your system does this and how to bypass it. If
there is a documented way of bypassing it, it is recommended
that you bypass it only for the httpd server process if
The canonical location for Apache's core-dump files is the
ServerRoot directory. As of Apache version 1.3, the location can
be set via the CoreDumpDirectory directive to a different
directory. Make sure that this directory is writable by the user
the server runs as (as opposed to the user the server is started
Question: When I run it under Linux I
get "shmget: function not found", what should I do?
Answer: Your kernel has been
built without SysV IPC support. You will have to rebuild the
kernel with that support enabled (it's under the "General Setup"
Question: Server hangs, or fails to
start, and/or error log fills with "fcntl: F_SETLKW: No record
locks available" or similar messages
Answer: These are symptoms of a fine locking problem, which
usually means that the server is trying to use a synchronization
file on an NFS filesystem.
Because of its parallel-operation model, the Apache Web server
needs to provide some form of synchronization when accessing
certain resources. One of these synchronization methods involves
taking out locks on a file, which means that the filesystem
whereon the lockfile resides must support locking. In many cases
this means it can't be kept on an NFS-mounted filesystem.
To cause the Web server to work around the NFS locking
limitations, include a line such as the following in your server
The directory should not be generally writable
(e.g., don't use /var/tmp).
How do I prevent Web access to a newly created domain, not yet
resolving in the nameservers, from showing a listing of the
directories of all domains on my server?
Place an index file in the DocumentRoot, /www/htdocs, of your
Does Apache on my server support Server Side Includes?
Yes. If you are having difficulty getting Server Side Includes (SSI's)
to work, add the following directives to /www/htdocs/.htaccess,
creating that file if it does not exist:
Options +Indexes +Includes +ExecCGI
AddType application/x-httpd-cgi .cgi .pl