ServerRoot httpd服務根目錄，包含的文件有，配置、錯誤、日誌

#
# Listen: Allows you to bind Apache to specific IP addresses and/or
# ports, instead of the default. See also the <VirtualHost>
# directive.
#
# Change this to Listen on specific IP addresses as shown below to 
# prevent Apache from glomming onto all bound IP addresses.
#
#Listen 12.34.56.78:80
Listen 80
 

Listen 制定監聽本機某個IP地址及端口。不指定IP時，默認監聽所有本機IP

#
# Dynamic Shared Object (DSO) Support
#
# To be able to use the functionality of a module which was built as a DSO you
# have to place corresponding `LoadModule‘ lines at this location so the
# directives contained in it are actually available _before_ they are used.
# Statically compiled modules (those listed by `httpd -l‘) do not need
# to be loaded here.
#
# Example:
# LoadModule foo_module modules/mod_foo.so
Include conf.modules.d/*.conf
 

LoadModule 啟用指定的DSO動態共享對象模塊，不指定時，僅僅加載靜態模塊
Include 指定靜態模塊路徑

#
# If you wish httpd to run as a different user or group, you must run
# httpd as root initially and it will switch.  
#
# User/Group: The name (or #number) of the user/group to run httpd as.
# It is usually good practice to create a dedicated user and group for
# running httpd, as with most system services.
#
User apache
Group apache

User、Group是本機運行apache服務的用戶名、組名。 不同系統服務，應該創建其特定的用戶來執行

# ‘Main‘ server configuration
#
# The directives in this section set up the values used by the ‘main‘
# server, which responds to any requests that aren‘t handled by a
# <VirtualHost> definition.  These values also provide defaults for
# any <VirtualHost> containers you may define later in the file.
#
# All of these directives may appear inside <VirtualHost> containers,
# in which case these default settings will be overridden for the
# virtual host being defined.
#

下面開始是主服務程序全局變量的配置，它們對每一個VirtualHost都有效。

#
# ServerAdmin: Your address, where problems with the server should be
# e-mailed.  This address appears on some server-generated pages, such
# as error documents.  e.g. [email protected]
#
ServerAdmin [email protected]

ServerAdmin 是管理員的個人郵箱

#
# ServerName gives the name and port that the server uses to identify itself.
# This can often be determined automatically, but we recommend you specify
# it explicitly to prevent problems during startup.
#
# If your host doesn‘t have a registered DNS name, enter its IP address here.
#
#ServerName www.example.com:80

ServerName 包含服務主機名（或IP）和端口號，它是httpd的身份標識，建議顯示地配置該參數

#
# Deny access to the entirety of your server‘s filesystem. You must
# explicitly permit access to web content directories in other 
# <Directory> blocks below.
#
<Directory />
    AllowOverride none
    Require all denied
</Directory>

Dicrectory 用於顯示地指定哪些目錄可以被httpd訪問，哪些不可以

#
# Note that from this point forward you must specifically allow
# particular features to be enabled - so if something‘s not working as
# you might expect, make sure that you have specifically enabled it
# below.
#

#
# DocumentRoot: The directory out of which you will serve your
# documents. By default, all requests are taken from this directory, but
# symbolic links and aliases may be used to point to other locations.
#
# 
DocumentRoot "/var/www/html"

DocumentRoot 是服務器提供訪問的網頁的默認根目錄，默認值是"/var/www/html。軟連接和匿名，可以用於指定到其它路徑

#
# Relax access to content within /var/www.
# 
<Directory "/var/www">
    AllowOverride None
    # Allow open access:
    Require all granted
</Directory>

# Further relax access to the default document root:
<Directory "/var/www/html">
    #
    # Possible values for the Options directive are "None", "All",
    # or any combination of:
    #   Indexes Includes FollowSymLinks SymLinksifOwnerMatch ExecCGI MultiViews
    #

Directory 配置項Options，指定目錄屬性，使用上述參數值，註意All不包含MultiViews，需顯示指定

      # Note that "MultiViews" must be named *explicitly* --- "Options All"
    # doesn‘t give it to you.
    #
    # The Options directive is both complicated and important.  Please see
    # http://httpd.apache.org/docs/2.4/mod/core.html#options
    # for more information.
    # 
    Options Indexes FollowSymLinks

    #
    # AllowOverride controls what directives may be placed in .htaccess files.
    # It can be "All", "None", or any combination of the keywords:
    #   Options FileInfo AuthConfig Limit
    #
    AllowOverride None

AllowOverride，控制哪些目錄可以存放到 .htaccess 文件中

    #
    # Controls who can get stuff from this server.
    Require all granted

誰可以stuff 

</Directory>

#
# DirectoryIndex: sets the file that Apache will serve if a directory
# is requested.
# 
<IfModule dir_module>
    DirectoryIndex index.html
</IfModule>

DirectoryIndex 設置返回值頁面，當請求一個路徑時

#
# The following lines prevent .htaccess and .htpasswd files from being 
# viewed by Web clients. 
#
<Files ".ht*">
    Require all denied
</Files>

禁止訪問 ht文件

#
# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a <VirtualHost>
# container, error messages relating to that virtual host will be
# logged here.  If you *do* define an error logfile for a <VirtualHost>
# container, that host‘s errors will be logged there and not here.
#
ErrorLog "logs/error_log"

錯誤日誌路徑全局默認值

#
# LogLevel: Control the number of messages logged to the error_log.
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
#
LogLevel warn

日誌級別

<IfModule log_config_module>
    #
    # The following directives define some format nicknames for use with
    # a CustomLog directive (see below).
    #
    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%h %l %u %t \"%r\" %>s %b" common

定義日誌格式的昵稱，方便使用 

    <IfModule logio_module>
      # You need to enable mod_logio.c to use %I and %O
      LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
    </IfModule>

定義登錄記錄格式昵稱

    # The location and format of the access logfile (Common Logfile Format).
    # If you do not define any access logfiles within a <VirtualHost>
    # container, they will be logged here.  Contrariwise, if you *do*
    # define per-<VirtualHost> access logfiles, transactions will be
    # logged therein and *not* in this file.
    #
    #CustomLog "logs/access_log" common

    訪問日誌全局默認文件的記錄格式，使用上面的昵稱

    # If you prefer a logfile with access, agent, and referer information
    # (Combined Logfile Format) you can use the following directive.
    #
    CustomLog "logs/access_log" combined

    訪問日誌全局默認文件的記錄格式，使用上面的昵稱

</IfModule>

<IfModule alias_module>
    #
    # Redirect: Allows you to tell clients about documents that used to 
    # exist in your server‘s namespace, but do not anymore. The client 
    # will make a new request for the document at its new location.
    # Example:
    # Redirect permanent /foo http://www.example.com/bar

    Redirect，重定向

    #
    # Alias: Maps web paths into filesystem paths and is used to
    # access content that does not live under the DocumentRoot.
    # Example:
    # Alias /webpath /full/filesystem/path

Alias 能夠引入不在默認網頁文檔根目錄下的其它文件，並起一個昵稱

    # If you include a trailing / on /webpath then the server will
    # require it to be present in the URL.  You will also likely
    # need to provide a <Directory> section to allow access to
    # the filesystem path.

    路徑結尾如果包含 斜線，應該確保該路徑可以被訪問，訪問一個目錄是可以的

    # ScriptAlias: This controls which directories contain server scripts. 
    # ScriptAliases are essentially the same as Aliases, except that
    # documents in the target directory are treated as applications and
    # run by the server when requested rather than as documents sent to the
    # client.  The same rules about trailing "/" apply to ScriptAlias
    # directives as to Alias.
    #
    ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"

ScriptAlias 用於引入不在默認網頁文檔根目錄的其它可執行文件，並起一個昵稱，可以是斜線結尾的

</IfModule>

#
# "/var/www/cgi-bin" should be changed to whatever your ScriptAliased
# CGI directory exists, if you have that configured.
#
<Directory "/var/www/cgi-bin">
    AllowOverride None
    Options None
    Require all granted
</Directory>

CGI 路徑如果存在，在這裏指定其位置，並設置相關參數值

<IfModule mime_module>
    #
    # TypesConfig points to the file containing the list of mappings from
    # filename extension to MIME-type.
    #
    TypesConfig /etc/mime.types

    文件mime類型解釋，參考源 

    #
    # AddType allows you to add to or override the MIME configuration
    # file specified in TypesConfig for specific file types.
    #
    #AddType application/x-gzip .tgz

增加文件類型

        # 

    # AddEncoding allows you to have certain browsers uncompress
    # information on the fly. Note: Not all browsers support this.
    #
    #AddEncoding x-compress .Z
    #AddEncoding x-gzip .gz .tgz

添加編碼類型，方便客戶端解壓

        # 

    # If the AddEncoding directives above are commented-out, then you
    # probably should define those extensions to indicate media types:
    #
    AddType application/x-compress .Z
    AddType application/x-gzip .gz .tgz

如果客戶端不支持AddEncoding,會無法解壓文件，在這裏增加文件類型

    #
    # AddHandler allows you to map certain file extensions to "handlers":
    # actions unrelated to filetype. These can be either built into the server
    # or added with the Action directive (see below)
    #
    # To use CGI scripts outside of ScriptAliased directories:
    # (You will also need to add "ExecCGI" to the "Options" directive.)
    #
    #AddHandler cgi-script .cgi

為特定文件添加解析程序，如果解析程序不在ScriptAliasd路徑，還需要啟用ExecCGI參數

    # For type maps (negotiated resources):
    #AddHandler type-map var

    添加類型映射解釋程序 

    #
    # Filters allow you to process content before it is sent to the client.
    #
    # To parse .shtml files for server-side includes (SSI):
    # (You will also need to add "Includes" to the "Options" directive.)
    #
    AddType text/html .shtml
    AddOutputFilter INCLUDES .shtml

處理發送給客戶端的內容

</IfModule>

#
# Specify a default charset for all content served; this enables
# interpretation of all content as UTF-8 by default.  To use the 
# default browser choice (ISO-8859-1), or to allow the META tags
# in HTML content to override this choice, comment out this
# directive:
#
AddDefaultCharset UTF-8

發送內容時，使用的編碼字符集，如果客戶端有其它字符集，註釋該行

<IfModule mime_magic_module>
    #
    # The mod_mime_magic module allows the server to use various hints from the
    # contents of the file itself to determine its type.  The MIMEMagicFile
    # directive tells the module where the hint definitions are located.
    #
    MIMEMagicFile conf/magic
</IfModule>

httpd自己的mime解釋源

#
# Customizable error responses come in three flavors:
# 1) plain text 2) local redirects 3) external redirects
#
# Some examples:
#ErrorDocument 500 "The server made a boo boo."
#ErrorDocument 404 /missing.html
#ErrorDocument 404 "/cgi-bin/missing_handler.pl"
#ErrorDocument 402 http://www.example.com/subscription_info.html

錯誤狀態碼 及解釋方式：文本、本地重定向、外部重定向

#
# EnableMMAP and EnableSendfile: On systems that support it, 
# memory-mapping or the sendfile syscall may be used to deliver
# files.  This usually improves server performance, but must
# be turned off when serving from networked-mounted 
# filesystems or if support for these functions is otherwise
# broken on your system.
# Defaults if commented: EnableMMAP On, EnableSendfile Off
#
#EnableMMAP off
EnableSendfile on

內存映射關閉、發送文件打開

# Supplemental configuration
#
# Load config files in the "/etc/httpd/conf.d" directory, if any.
IncludeOptional conf.d/*.conf

補充配置：如果confd路徑有配置文件，加載它

apache配置文件逐行解讀