Apache HTTP Server¶

Apache httpd is the long-standing, modular web server that powers a huge share of the internet. Its big differentiators are a rich module ecosystem and per-directory .htaccess overrides. This page covers installing httpd, its configuration layout, DocumentRoot, a basic <VirtualHost>, enabling modules, and .htaccess.

Tested on

AlmaLinux 9 / RHEL 9 with the httpd package from AppStream. Debian/Ubuntu uses the apache2 package and tooling — notes are inline.

When to choose Apache vs nginx¶

Choose Apache when you want .htaccess per-directory config (common in shared hosting and many PHP apps), mod_php, or a specific Apache module.
Choose nginx for high-concurrency static serving and reverse proxying with the lowest memory footprint. See Nginx.

Apache's concurrency behaviour is set by its MPM (Multi-Processing Module):

MPM	Model	Notes
`prefork`	One process per connection, no threads	Required by the non-thread-safe `mod_php`; heaviest on memory
`worker`	Threads within processes	Lighter than prefork
`event`	Like worker but offloads keep-alive handling	Default on RHEL 9; best for high concurrency

RHEL 9 ships the event MPM by default. If you need mod_php you must switch to prefork — but the modern recommendation is PHP-FPM instead (see PHP & PHP-FPM), which works with any MPM.

Install Apache httpd¶

AlmaLinux / RHEL 9Debian / Ubuntu

sudo dnf install -y httpd

# Enable on boot and start now
sudo systemctl enable --now httpd

systemctl status httpd

The service and binary are called httpd on RHEL.

sudo apt update
sudo apt install -y apache2
sudo systemctl enable --now apache2

The service and binary are called apache2 on Debian.

Open the firewall¶

sudo firewall-cmd --add-service=http --add-service=https --permanent
sudo firewall-cmd --reload
sudo firewall-cmd --list-services

Browse to http://<server-ip>/ — you should see the Apache test page. (Debian/Ubuntu with UFW: sudo ufw allow 'Apache Full'.) See Firewalls.

Configuration layout¶

AlmaLinux / RHEL 9Debian / Ubuntu

/etc/httpd/
├── conf/
│   └── httpd.conf          # main config (global settings, default DocumentRoot)
├── conf.d/                 # drop-in *.conf files (vhosts, ssl.conf, etc.)
├── conf.modules.d/         # *.conf files that LoadModule for installed modules
└── /var/www/html/          # default DocumentRoot

httpd.conf ends with IncludeOptional conf.d/*.conf, so any .conf file you drop in conf.d/ is loaded. Modules are loaded by files in conf.modules.d/.

/etc/apache2/
├── apache2.conf            # main config
├── ports.conf              # Listen directives
├── sites-available/        # vhost files (write here)
├── sites-enabled/          # symlinks created by a2ensite
├── mods-available/         # all available modules
└── mods-enabled/           # symlinks created by a2enmod
└── /var/www/html/          # default DocumentRoot

Debian splits everything into available/enabled pairs managed by helper commands:

sudo a2ensite mysite      # enable a site (symlink into sites-enabled)
sudo a2dissite mysite     # disable it
sudo a2enmod rewrite      # enable a module
sudo a2dismod rewrite     # disable it
sudo systemctl reload apache2   # apply

DocumentRoot and a basic VirtualHost¶

DocumentRoot is the directory Apache serves files from. The global default is /var/www/html. To host a site under its own root, define a <VirtualHost>.

1. Create the site files¶

sudo mkdir -p /var/www/example.com
echo '<h1>Hello from Apache on AlmaLinux 9</h1>' | sudo tee /var/www/example.com/index.html

2. SELinux: label the custom DocumentRoot (RHEL/AlmaLinux)¶

Apache (like nginx) is confined by SELinux. A DocumentRoot outside /var/www/html must carry the httpd_sys_content_t type or you will get 403 Forbidden:

sudo semanage fcontext -a -t httpd_sys_content_t "/var/www/example.com(/.*)?"
sudo restorecon -Rv /var/www/example.com

Outbound connections

If Apache must reach a network service (proxying, remote DB, sending mail from an app), allow it persistently: sudo setsebool -P httpd_can_network_connect 1. See SELinux.

3. Create the vhost file¶

On RHEL/AlmaLinux, create /etc/httpd/conf.d/example.com.conf:

<VirtualHost *:80>
    ServerName   example.com
    ServerAlias  www.example.com
    DocumentRoot /var/www/example.com

    <Directory /var/www/example.com>
        # Allow Apache to serve this directory
        Require all granted

        # Control whether .htaccess can override settings here (see below)
        AllowOverride All
    </Directory>

    # Per-site logs
    ErrorLog  /var/log/httpd/example.com-error.log
    CustomLog /var/log/httpd/example.com-access.log combined
</VirtualHost>

On Debian, write this to /etc/apache2/sites-available/example.com.conf (logs go to /var/log/apache2/), then run sudo a2ensite example.com.

Enabling modules¶

Apache's functionality comes from modules. On RHEL many are installed and loaded by default; install extra ones with dnf.

AlmaLinux / RHEL 9Debian / Ubuntu

# Example: SSL and rewrite support
sudo dnf install -y mod_ssl

# List currently loaded modules
httpd -M

mod_rewrite is included in the base httpd package and loaded via conf.modules.d/. To confirm: httpd -M | grep rewrite.

sudo a2enmod ssl rewrite
sudo systemctl reload apache2
apache2ctl -M        # list loaded modules

.htaccess and AllowOverride¶

.htaccess is a per-directory config file. Apache reads it on every request for that directory tree — handy on shared hosting where you cannot edit the main config, but slower than central config.

.htaccess only takes effect if AllowOverride permits it for that directory:

`AllowOverride` value	Effect
`None`	`.htaccess` is ignored entirely (default on RHEL 9 for `/var/www/html`)
`All`	All directives allowed in `.htaccess`
`FileInfo`, `AuthConfig`, etc.	Allow only specific classes of directive

Example .htaccess in /var/www/example.com/ that needs mod_rewrite and AllowOverride All:

# /var/www/example.com/.htaccess
RewriteEngine On
# Redirect everything that is not a real file to index.php (common front-controller pattern)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ index.php [L]

Performance

On servers you fully control, prefer putting these rules directly in the <Directory> block and leaving AllowOverride None. This avoids Apache walking the directory tree looking for .htaccess files on every request.

Test the config, then reload¶

Never reload blindly — validate first:

# RHEL/AlmaLinux
sudo apachectl configtest
# (equivalent: sudo httpd -t)

Expected:

Syntax OK

Then apply with a graceful reload:

sudo systemctl reload httpd      # RHEL/AlmaLinux
# sudo systemctl reload apache2  # Debian

On Debian the test command is sudo apache2ctl configtest.

Logs¶

AlmaLinux / RHEL 9Debian / Ubuntu

/var/log/httpd/access_log     # all requests
/var/log/httpd/error_log      # errors and startup messages
/var/log/httpd/example.com-*  # the per-vhost logs from our config

/var/log/apache2/access.log
/var/log/apache2/error.log

# Tail the error log while testing (RHEL path shown)
sudo tail -f /var/log/httpd/error_log

Verify your work¶

# 1. Service enabled and active
systemctl is-enabled httpd && systemctl is-active httpd

# 2. Config syntax is OK
sudo apachectl configtest

# 3. Firewall allows HTTP/HTTPS
sudo firewall-cmd --list-services | grep http

# 4. The vhost responds
curl -H 'Host: example.com' http://localhost/
# -> <h1>Hello from Apache on AlmaLinux 9</h1>

# 5. Custom DocumentRoot has the right SELinux label
ls -Zd /var/www/example.com   # -> httpd_sys_content_t

Summary¶

Install with dnf install httpd (service: httpd) on RHEL/AlmaLinux or apt install apache2 (service: apache2) on Debian.
RHEL config lives in /etc/httpd/conf/httpd.conf plus drop-ins in conf.d/; Debian uses /etc/apache2 with a2ensite/a2enmod helpers.
DocumentRoot sets the served directory; <VirtualHost> hosts a site under its own root and ServerName.
.htaccess only works where AllowOverride allows it; prefer central config when you control the server.
Custom DocumentRoots on RHEL/AlmaLinux need the httpd_sys_content_t SELinux label.
Always apachectl configtest before systemctl reload httpd; logs are in /var/log/httpd/.

Next: add PHP with PHP & PHP-FPM, host multiple sites in Virtual Hosts, or enable HTTPS in HTTPS with Let's Encrypt.

Apache HTTP Server¶

When to choose Apache vs nginx¶

Install Apache httpd¶

Open the firewall¶

Configuration layout¶

DocumentRoot and a basic VirtualHost¶

1. Create the site files¶

2. SELinux: label the custom DocumentRoot (RHEL/AlmaLinux)¶

3. Create the vhost file¶

Enabling modules¶

.htaccess and AllowOverride¶

Test the config, then reload¶

Logs¶

Verify your work¶

Summary¶

Test yourself¶