Install Apache On CentOS 7

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Introduction #

The Apache HTTP Server is a free and open-source cross-platform web server software, released under the terms of Apache License 2.0. Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation.


In this guide, you will install an Apache web server with virtual hosts on your CentOS 7 server.

Prerequisites #

Make sure you have the following things taken care of before you start:


  • CentOS 7 installed on your system.
  • Root privileges on your system.

Installing Apache #

We will use the yum package manager to install Apache.


This tutorial should be ran in the context of the user creating the server, using sudo As you will see later, permissions will be set based on the context of the current user. First, we will update the local Apache httpd package index to reflect the latest upstream changes:

  • sudo yum update httpd

Once the packages are updated, install the Apache package:

  • sudo yum install httpd

After confirming the installation, yum will install Apache and all required dependencies.

Configuring the Firewall #

A firewall establishes a barrier between a trusted network and an untrusted network, such as the Internet. CentOS ships with a firewall called firewalld. A tool called firewall-cmd can be used to configure your firewall policies. Our basic strategy will be to lock down everything that we do not have a good reason to keep open. First install firewalld:

  • sudo yum install firewalld

The firewalld service has the ability to make modifications without dropping current connections, so we can turn it on before creating our exceptions:

  • sudo systemctl start firewalld

First, you’ll need to open up ports 80 and 443 to allow Apache to serve requests over HTTP and HTTPS respectively.

  • sudo firewall-cmd --permanent --add-service=http

If you plan to configure Apache to serve content over HTTPS, you will also want to open up port 443 by enabling the https service:

  • sudo firewall-cmd --permanent --add-service=https

Next, reload the firewall to put these new rules into effect:

  • sudo firewall-cmd --reload

After the firewall reloads, you are ready to start the service and check the web server.

Checking your Web Server #

Start your web server:

  • sudo systemctl start httpd

Verify that the service is running with the following command:

  • sudo systemctl status httpd

You will see an active status when the service is running:

Output
Redirecting to /bin/systemctl status httpd.service ● httpd.service - The Apache HTTP Server Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled) Active: active (running) since Wed 2019-02-20 01:29:08 UTC; 5s ago Docs: man:httpd(8) man:apachectl(8) Main PID: 1290 (httpd) Status: "Processing requests..." CGroup: /system.slice/httpd.service ├─1290 /usr/sbin/httpd -DFOREGROUND ├─1291 /usr/sbin/httpd -DFOREGROUND ├─1292 /usr/sbin/httpd -DFOREGROUND ├─1293 /usr/sbin/httpd -DFOREGROUND ├─1294 /usr/sbin/httpd -DFOREGROUND └─1295 /usr/sbin/httpd -DFOREGROUND ...

Notice the highlighted portion that says active. That is a good sign.


You can access the default Apache landing page to confirm that the software is running properly through your IP address. If you do not know your server’s IP address, you can get it a few different ways from the command line.


Type this at your server’s command prompt:

  • hostname -I

This command will display all of the host’s network addresses, so you will get back a few IP addresses separated by spaces. You can try each in your web browser to see if they work.

When you have your server’s IP address, enter it into your browser’s address bar:

http://your_server_ip

You’ll see the default CentOS 7 Apache web page:

Default Apache page for CentOS 7

This page indicates that Apache is working correctly. It also includes some basic information about important Apache files and directory locations. Now that the service is installed and running, you can now use different systemctl commands to manage the service.

Managing the Apache Process #

If you're not familiar with man pages, type the following to get a background on the different available commands. If you are familiar with them, you can skip to the next section

  • man systemctl
  • man httpd

Here are some commands of note that are pretty self explanatory:

  • sudo systemctl stop httpd
  • sudo systemctl start httpd
  • sudo systemctl restart httpd
  • sudo systemctl reload httpd
  • sudo systemctl disable httpd
  • sudo systemctl enable httpd

The default configuration for Apache will allow your server to host a single website. If you plan on hosting multiple domains on your server, you will need to configure virtual hosts on your Apache web server.

Setting Up Virtual Hosts #

When using the Apache web server, you can use virtual hosts to manage a shared hosting server. In this step, you will set up a domain called example.com, but you should replace this with your own domain name.


Apache on CentOS 7 has one server block enabled by default that is configured to serve documents from the /var/www/html directory. To enable multiple websites to be hosted, you will create a directory structure within /var/www for the example.com site, leaving /var/www/html in place as the default directory to be served if a client request doesn’t match any other sites.


Create the html directory for example.com as follows, using the -p flag to create any necessary parent directories:

  • sudo mkdir -p /var/www/example.com/html

Create an additional directory to store log files for the site:

  • sudo mkdir -p /var/www/example.com/log

Next, assign ownership of the html directory with the $USER environmental variable This is where context matters. If you are running as root, this command will do nothing. So, you would have to change the portion that says $USER to [the logged in user name]:

  • sudo chown -R $USER:$USER /var/www/example.com/html

Make sure that your web root has the default permissions set:

  • sudo chmod -R 755 /var/www

Next, create a sample index.html page using vi or your favorite editor:

  • sudo vi /var/www/example.com/html/index.html

Press i to switch to INSERT mode and add the following sample HTML to the file:

/var/www/example.com/html/index.html
<html>
  <head>
    <title>Welcome to Example.com!</title>
  </head>
  <body>
    <h1>Success! The example.com virtual host is working!</h1>
  </body>
</html>

Save and close the file by pressing ESC, typing :wq!, and pressing ENTER.

With your site directory and sample index file in place, you are almost ready to create the virtual host files. Virtual host files specify the configuration of your separate sites and tell the Apache web server how to respond to various domain requests.


Before you create your virtual hosts, you will need to create a sites-available directory to store them in. You will also create the sites-enabled directory that tells Apache that a virtual host is ready to serve to visitors. The sites-enabled directory will hold symbolic links to virtual hosts that we want to publish. Create both directories with the following command:

  • sudo mkdir /etc/httpd/sites-available /etc/httpd/sites-enabled

Next, you will tell Apache to look for virtual hosts in the sites-enabled directory. The * prefix indicates that it will search all files in the directory. To accomplish this, edit Apache’s main configuration file and add a line declaring an optional directory for additional configuration files:

  • sudo vi /etc/httpd/conf/httpd.conf

Add this line to the end of the file:

IncludeOptional sites-enabled/*.conf

Save and close the file when you are done adding that line. Now that you have your virtual host directories in place, you will create your virtual host file.


Start by creating a new file in the sites-available directory:

  • sudo vi /etc/httpd/sites-available/example.com.conf

Add in the following configuration block, and change the example.com domain to your domain name:

/etc/httpd/sites-available/example.com.conf
<VirtualHost *:80>
    ServerName www.example.com
    ServerAlias example.com
    DocumentRoot /var/www/example.com/html
    ErrorLog /var/www/example.com/log/error.log
    CustomLog /var/www/example.com/log/requests.log combined
</VirtualHost>

This will tell Apache where to find the root directly that holds the publicly accessible web documents. It also tells Apache where to store error and request logs for this particular site.

Save and close the file when you are finished.


Now repeat the process for port 443:

  • sudo vi /etc/httpd/sites-available/example.com.ssl.conf
/etc/httpd/sites-available/example.com.conf
<VirtualHost *:443>
    ServerName www.example.com
    ServerAlias example.com
    DocumentRoot /var/www/example.com/html
    ErrorLog /var/www/example.com/log/error.log
    CustomLog /var/www/example.com/log/requests.log combined
</VirtualHost>

Now that you have created the virtual host files, you will enable them so that Apache knows to serve them to visitors. To do this, create a symbolic link for each virtual host in the sites-enabled directory:

  • sudo ln -s /etc/httpd/sites-available/example.com.conf /etc/httpd/sites-enabled/example.com.conf
  • sudo ln -s /etc/httpd/sites-available/example.com.ssl.conf /etc/httpd/sites-enabled/example.com.ssl.conf

Your virtual host is now configured and ready to serve content. Before restarting the Apache service, let’s make sure that SELinux has the correct policies in place for your virtual hosts.

SELinux is configured to work with the default Apache configuration. Since you set up a custom log directory in the virtual hosts configuration file, you will receive an error if you attempt to start the Apache service. To resolve this, you need to update the SELinux policies to allow Apache to write to the necessary files. SELinux brings heightened security to your CentOS 7 environment, therefore it is not recommended to completely disable the kernel module.

There are different ways to set policies based on your environment’s needs, as SELinux allows you to customize your security level. This step will cover two methods of adjusting Apache policies: universally and on a specific directory. Adjusting policies on directories is more secure, and is therefore the recommended approach.

Adjusting Apache Policies Universally #

Setting the Apache policy universally will tell SELinux to treat all Apache processes identically by using the httpd_unified boolean. While this approach is more convenient, it will not give you the same level of control as an approach that focuses on a file or directory policy.

Run the following command to set a universal Apache policy:

  • sudo setsebool -P httpd_unified 1

The setsebool command changes SELinux boolean values. The -P flag will update the boot-time value, making this change persist across reboots. httpd_unified is the boolean that will tell SELinux to treat all Apache processes as the same type, so you enabled it with a value of 1.

Adjusting Apache Policies on a Directory #

Individually setting SELinux permissions for the /var/www/example.com/log directory will give you more control over your Apache policies, but may also require more maintenance. Since this option is not universally setting policies, you will need to manually set the context type for any new log directories specified in your virtual host configurations.

First, check the context type that SELinux gave the /var/www/example.com/log directory:

  • sudo ls -dZ /var/www/example.com/log/

This command lists and prints the SELinux context of the directory. You will see output similar to the following:

Output
drwxr-xr-x. root root unconfined_u:object_r:httpd_sys_content_t:s0 /var/www/example.com/log/

The current context is httpd_sys_content_t, which tells SELinux that the Apache process can only read files created in this directory. In this tutorial, you will change the context type of the /var/www/example.com/log directory to httpd_log_t. This type will allow Apache to generate and append to web application log files:

  • sudo semanage fcontext -a -t httpd_log_t "/var/www/example.com/log(/.*)?"

Next, use the restorecon command to apply these changes and have them persist across reboots:

  • sudo restorecon -R -v /var/www/example.com/log

The -R flag runs this command recursively, meaning it will update any existing files to use the new context. The -v flag will print the context changes the command made. You will see the following output confirming the changes:

Output
restorecon reset /var/www/example.com/log context unconfined_u:object_r:httpd_sys_content_t:s0->unconfined_u:object_r:httpd_log_t:s0

You can list the contexts once more to see the changes:

  • sudo ls -dZ /var/www/example.com/log/

The output reflects the updated context type:

Output
drwxr-xr-x. root root unconfined_u:object_r:httpd_log_t:s0 /var/www/example.com/log

Now that the /var/www/example.com/log directory is using the httpd_log_t type, you are ready to test your virtual host configuration.

Once the SELinux context has been updated with either method, Apache will be able to write to the /var/www/example.com/log directory. You can now successfully restart the Apache service:

  • sudo systemctl restart httpd

List the contents of the /var/www/example.com/log directory to see if Apache created the log files:

  • ls -lZ /var/www/example.com/log

You’ll see that Apache was able to create the error.log and requests.log files specified in the virtual host configuration:

Output
-rw-r--r--. 1 root root 0 Feb 26 22:54 error.log -rw-r--r--. 1 root root 0 Feb 26 22:54 requests.log

Now that you have your virtual host set up and SELinux permissions updated, Apache will now serve your domain name. You can test this by navigating to http://example.com, where you should the page you built above.


This confirms that your virtual host is successfully configured and serving content.

Conclusion #

In this tutorial, you installed and managed the Apache web server. Now that you have your web server installed, you have many options for the type of content you can serve and the technologies you can use to create a richer experience.

Sources #

Wikipedia - Apache Web Server
Digital Ocean - Installing Apache Web Server on Centos 7
Digital Ocean - Additional Recommended Steps for New CentOS 7

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