diff options
Diffstat (limited to 'debian/apache2.README.Debian')
| -rw-r--r-- | debian/apache2.README.Debian | 444 |
1 files changed, 444 insertions, 0 deletions
diff --git a/debian/apache2.README.Debian b/debian/apache2.README.Debian new file mode 100644 index 0000000..5597227 --- /dev/null +++ b/debian/apache2.README.Debian @@ -0,0 +1,444 @@ +Contents +======== + + Apache2 Configuration under Debian GNU/Linux + Files and Directories in '/etc/apache2' + Tools + + Using mod_cache_disk + + SSL + Enabling SSL + Creating self-signed certificates + SSL workaround for MSIE + + Suexec + + Documentation + + Upgrades + + Common Problems + + For Developers + +Apache2 Configuration under Debian GNU/Linux +============================================ + +Debian's default Apache2 installation attempts to make adding and +removing modules, virtual hosts, and extra configuration directives as +flexible as possible, in order to make automating the changes and +administering the server as easy as possible. + +Please be aware that this layout is quite different from the standard +Apache configuration. Due to the use of environment variables, apache2 +needs to be started/stopped with '/etc/init.d/apache2', apachectl, or +apache2ctl. Calling '/usr/bin/apache2' directly will not work with the +default configuration. To call apache2 with specific command line +arguments, just call apache2ctl with the same arguments. + +Files and Directories in '/etc/apache2': +--------------------------------------- + +apache2.conf + + This is the main configuration file. It does not include any + actual configuration we expect to be adapted on your site, so + where possible please do not touch it. This file is the + foundation stone of the Apache configuration in Debian and should + be up to date after upgrades to make sure all configuration pieces + are properly included. + + If you want to extend the global configuration, you can customize + the Apache web server by including configuration files through the + conf-available mechanism. To change listening ports and socket + configuration use ports.conf (see below). + +ports.conf + + Configuration directives for which ports and IP addresses to + listen to. + +magic + + Patterns for mod_mime_magic. This is not compatible with the format + used by current versions of the file/libmagic packages. + +envvars + + This contains environment variables that may be used in the + configuration. Some settings, like user and pid file, need to + go in here so that other scripts can use them. It can also + be used to change some default settings used by apache2ctl, + including the ulimit value for the maximum number of open files. + The default LANG=C setting is also here, and can be changed to a + different language. + +conf-available/ + + Files in this directory are included in the global server scope by + this line in apache2.conf: + + # Include generic snippets of statements + IncludeOptional conf-enabled/*.conf + + This is a good place to add additional configuration + directives. All configuration snippets need a '.conf' suffix to be + included as actual configuration. The local administrator should + use file names starting with 'local-' to avoid name clashes with + files installed by packages. + + Configuration snippets can be enabled and disabled by using the + a2enconf and a2disconf executables. This works similarly to the + approach used for modules and sites below. + + Configuration snippets can of course also be included in individual + virtual hosts. + +conf-enabled/ + + Like mods-enabled/ and sites-enabled/, a piece of configuration is + enabled by symlinking a file from conf-available/ into this + directory. The a2enconf helper is provided to assist this task. + +mods-available/ + + This directory contains a series of .load and .conf files. + The .load files contain the Apache configuration directive + necessary to load the module in question. The corresponding + .conf files contain configuration directives necessary to + utilize the module in question. + +mods-enabled/ + + To actually enable a module for Apache2, it is necessary to + create a symlink in this directory to the .load (and .conf, if + it exists) files associated with the module in + mods-available/. For example: + + cgi.load -> /etc/apache2/mods-available/cgi.load + + The a2enmod helper can be used to enable a module. + +sites-available/ + + Like mods-available/, except that it contains configuration + directives for different virtual hosts that might be used with + apache2. Note that the hostname doesn't have to correspond + exactly with the filename. '000-default.conf' is the default + host which is provided by Debian. + +sites-enabled/ + + Similar in functionality to mods-enabled/, sites-enabled + contains symlinks to sites in sites-available/ that the + administrator wishes to enable. + + Apache uses the first VirtualHost that matches the IP/Port + as default for named virtual hosts. Therefore the 'default' + site should be called '000-default' to make sure it sorts before + other sites. + + Example: + dedasys.conf -> /etc/apache2/sites-available/dedasys.conf + + The a2ensite helper can be used to enable a site. + +The Include directives ignore files with names that do not end with a +.conf suffix. This behavior has changed from previous releases! + +In some cases you may want to enable a specific piece of configuration +(think of files shipped in conf-available/) for a particular virtual +host only and not globally as is our default. In such cases you can +disable the configuration at a global scope for example by doing + + a2disconf some-configuration + +Then it can be included in a particular virtual host within a file in +sites-enabled/. You may want to add + + Include conf-available/some-configuration.conf + +in that site configuration. However, be careful, as this may not work for +some configurations, depending on the context and implications of some +directives. + + +Tools +----- + +a2enmod and a2dismod are available for enabling and disabling modules utilizing +the above configuration system. + +a2ensite and a2dissite do essentially the same thing as the above tools, but +for sites rather than modules. Finally a2enconf and a2disconf are the +corresponding tools for configuration snippets. + +a2query is a helper script providing runtime information about the running +server instance. For example it can be used to query enabled modules, the +selected MPM, and other information. This tool is primarily meant for package +maintainers who need to interact with the Apache packages to activate +their configurations upon package installation, but it can be used by users +as well. + +apxs2 -a/-A is modified to use a2enmod to activate newly installed modules. + + +Using mod_cache_disk +==================== + +To ensure that the disk cache does not grow indefinitely, htcacheclean is +started when mod_cache_disk is enabled. Both daemon and cron (daily) mode +are supported. The configuration (run mode, cache size, etc.) is in +'/etc/default/apache-htcacheclean'. + +Normally, htcacheclean is automatically started and stopped by +'/etc/init.d/apache2'. However, if you change the state of mod_cache_disk or +the configuration of htcacheclean while apache2 is running, you may need to +manually start/stop htcacheclean with "/etc/init.d/apache2 start-htcacheclean" +or "/etc/init.d/apache2 stop-htcacheclean". + +Note that mod_cache_disk was named mod_disk_cache in versions 2.2 and earlier. + + +SSL +=== + +Enabling SSL +------------ + +To enable SSL, type (as user root): + + a2ensite default-ssl + a2enmod ssl + +If you want to use self-signed certificates, you should install the ssl-cert +package (see below). Otherwise, just adjust the SSLCertificateKeyFile and +SSLCertificateFile directives in '/etc/apache2/sites-available/default-ssl.conf' +to point to your SSL certificate. Then restart apache: + + service apache2 restart + +The SSL key file should only be readable by root; the certificate file may be +globally readable. These files are read by the Apache parent process which runs +as root, and it is therefore not necessary to make the files readable by the +www-data user. + +Creating self-signed certificates +--------------------------------- + +If you install the ssl-cert package, a self-signed certificate will be +automatically created using the hostname currently configured on your computer. +You can recreate that certificate (e.g. after you have changed '/etc/hosts' or +DNS to give the correct hostname) as user root with: + + make-ssl-cert generate-default-snakeoil --force-overwrite + +To create more certificates with different host names, you can use + + make-ssl-cert /usr/share/ssl-cert/ssleay.cnf /path/to/cert-file.crt + +This will ask you for the hostname and place both SSL key and certificate in +the file '/path/to/cert-file.crt'. Use this file with the SSLCertificateFile +directive in the Apache config (you don't need the SSLCertificateKeyFile in +this case as it also contains the key). The file '/path/to/cert-file.crt' +should only be readable by root. A good directory to use for the additional +certificates/keys is '/etc/ssl/private'. + +SSL workaround for MSIE +----------------------- + +The SSL workaround for MS Internet Explorer needs to be added to your SSL +VirtualHost section (it was previously in ssl.conf but caused keepalive to be +disabled even for non-SSL connections): + + BrowserMatch "MSIE [2-6]" \ + nokeepalive ssl-unclean-shutdown \ + downgrade-1.0 force-response-1.0 + BrowserMatch "MSIE [17-9]" ssl-unclean-shutdown + +The default SSL virtual host in '/etc/apache2/sites-available/default-ssl.conf' +already contains this workaround. + + +Suexec +====== + +Debian ships two version of the suexec helper program required by +mod_suexec. It is not installed by default, to avoid possible security +issues. The package apache2-suexec-pristine contains the standard version +that works only with document root /var/www, userdir suffix public_html, +and Apache run user www-data. The package apache2-suexec-custom contains a +customizable version that can be configured with a config file to use +different settings (like /srv/www as document root). For more information +see the suexec(8) man page in the apache2-suexec-custom package. + +Since apache2-suexec-custom has received less testing and might be slightly +slower, apache2-suexec is the recommended version unless you need the features +from apache2-suexec-custom. + +Starting with Apache 2.4 both alternatives can be installed at the same +time and the default suexec mechanism can be picked by using the +update-alternatives(8) system. + + +Unicode File Name Normalization +=============================== + +Using Apache with the document root on a file system that does unicode +normalization on the filenames can cause security issues. In Debian, +this affects ZFS with the non-default option to enable filename normalization, +and HFS+. It is strongly recommended not to use Apache with such file systems. +More information about this issue can be found by searching the web for +CVE-2013-0966. + + +Documentation +============= + +The full Apache 2 documentation can be found on the web at + +http://httpd.apache.org/docs/2.4/ + +or, if you have installed the apache2-doc package, in + +/usr/share/doc/apache2-doc/manual/ + +or at + +http://localhost/manual/ + +There is also a wiki that contains useful information: + +http://wiki.apache.org/httpd/ + +Some hints about securing Apache 2 on Debian are available at + +http://wiki.debian.org/Apache/Hardening + + +Upgrades +======== + +Changes in the Apache packages that require manual configuration adjustments +are announced in NEWS.Debian. Installing the apt-listchanges package is +recommended. It will display the relevant NEWS.Debian sections before +upgrades. + + +Multiple instances +================== + +There is some support for running multiple instances of Apache2 on the same +machine. See '/usr/share/doc/apache2/README.multiple-instances' for more +information. + + +Common Problems +=============== + +1) Error message "Could not reliably determine the server's fully qualified +domain name, using 127.0.0.1 for ServerName" during start + +This can usually be ignored but it means that Apache httpd was unable to obtain +a fully-qualified hostname by doing a reverse lookup on your server's IP +address. You may want to add the fully-qualified hostname to '/etc/hosts'. +An alternative is to specify "ServerName 127.0.0.1" in the global server +context of the configuration, e.g. in +'/etc/apache2/conf-enabled/local-servername.conf'. + +2) Error message "mod_rewrite: could not create rewrite_log_lock" + +This probably means that there are some stale SYSV semaphores around. This +usually happens after apache2 has been killed with kill -9 (SIGKILL). You can +clean up the semaphores with: + + ipcs -s | grep www-data | awk ' { print $2 } ' | xargs ipcrm sem + +3) Message "File does not exist: /etc/apache2/htdocs" in error log + +In most cases this means that no matching VirtualHost definition could be +found for an incoming request. Check that the target IP address/port and the +name in the Host: header of the request actually match one of the virtual +hosts. + +4) Message "Couldn't create pollset in child; check user or system limits" in +error log + +On Linux kernels since 2.6.27.8, the value in + + /proc/sys/fs/epoll/max_user_instances + +needs to be larger than + + for prefork/itk MPM: 2 * MaxClients + for worker/event MPM: MaxClients + MaxClients/ThreadsPerChild + +It can be set on boot by adding a line like + + fs.epoll.max_user_instances=1024 + +to '/etc/sysctl.conf'. + +There are several other error messages related to creating a pollset that can +appear for the same reason. + +On the other hand, errors about adding to a pollset are related to the setting +fs.epoll.max_user_watches. On most systems, max_user_watches should be high +enough by default. + +5) Message "Server should be SSL-aware but has no certificate configured" in +error log + +Since 2.2.12, Apache is stricter about certain misconfigurations concerning +name based SSL virtual hosts. See NEWS.Debian.gz for more details. + +6) Apache does not pass Authorization header to CGI scripts + +This is intentional to avoid security holes. If you really want to change it, +you can use mod_rewrite: + + RewriteCond %{HTTP:Authorization} (.*) + RewriteRule . - [env=HTTP_AUTHORIZATION:%1] + +7) mod_dav is behaving strangely + +In general, if you use mod_dav_fs, you need to disable multiviews and script +execution for that directory. For example: + + <Directory /var/www/dav> + Dav on + Options -MultiViews -ExecCGI + SetHandler none + <IfModule mod_php5.c> + php_admin_value engine Off + </IfModule> + </Directory> + +8) Message "apache2: bad user name ${APACHE_RUN_USER}" when starting apache2 +directly + +Use apache2ctl (it accepts all the same options as apache2). + +9) A PUT with mod_dav_fs fails with "Unable to PUT new contents for /... +[403, #0]" even if Apache has permission to write the file. + +Apache also needs write permission to the directory containing the file, in +order to replace it atomically. + +10) When starting/reloading Apache, there is the error message +"ulimit: open files: cannot modify limit: Operation not permitted" + +If you are running Apache in a vserver environment, the start script may not +be allowed to set the maximum number of open files. You should adjust +APACHE_ULIMIT_MAX_FILES in /etc/apache2/envvars to your setup. You can +disable changing the limits by setting APACHE_ULIMIT_MAX_FILES=true . + + +For Developers +============== + +The Apache 2 web server package provides several helpers to assist +packagers to interact with the web server for both, build and installation +time. Please refer to the PACKAGING file in the apache2 package for +detailed information. |