Draft: Install Nagios on Debian 12 & Ubuntu 22.04

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Created draft of title subject matter based on updates to Debian and Ubuntu:
Updated Metadata
Added contributor onboarding support notes

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	- Missing package: One of the listed packages may not be available in your distro's repositories.
	This command helps you confirm whether the packages exist in your distro's repositories.

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	Or any of these common issues:
	Common issues and how to resolve them:
	- **Missing package**: One or more packages may not be available in your distro's repositories. Double-check your `/etc/apt/sources.list` and run `sudo apt update` to refresh the cache.

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	- Permission issues: If you're not using `sudo`, you might see permission denied.
	- **Permission denied**: If you didn't use `sudo`, the install will fail. Always run `apt` commands with elevated privileges.

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	- Network: A broken internet connection or unreachable mirror can cause download failures.
	- Network: A broken internet connection or unreachable mirror can prevent downloads. Try pinging a known host or switching mirrors.

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	- Broken dependencies: If your system has conflicting packages or unmet dependencies, `apt` will usually suggest a fix. Then isolate the problem by installing packages one at a time:
	- Broken dependencies: If your system has conflicting packages or unmet dependencies, `apt` usually suggests a fix. To isolate the problem, install packages one at a time:

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	Using the `-c ` flag creates the file if it doesn't exist.
	Using the `-c ` flag creates the file if it doesn't exist **and overwrites it** if it already contains users. To preserve existing entries, omit `-c`.

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	Open `/etc/nagios4/apache2/conf` in your preferred editor and make the following changes:
	Open `/etc/nagios4/apache2/sites-available/000-default.conf` in your preferred editor with elevated privileges (e.g., `sudo nano`) and make the following changes: (Note: If `/etc/apache2/conf-available/nagios4.conf` doesn't exist it will show `[ New File ]` just above the commands line which means you're are creating it manually. Copy the config block example shown below and paste it in, then use `Ctrl + O` and exit with `Ctrl + X`.)
	{{< note>}} For Debian 12/Ubuntu 22.04, Nagios web access is typically configured in `/etc/apache2/sites-available/000-default.conf`. Some older guides may reference `/etc/nagios4/apache2/conf`, which may not exist or be used in modern setups.
	{{</ note>}}

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	Inside `<DirectoryMatch>` block:
	Example: Inside `<DirectoryMatch>` block:
	Following the lines:
	ServerAdmin webmaster@localhost
	DocumentRoot /var/www/html
	Copy or type in your content:
	#Restrict access to Nagios CGI interface
	<Directory "/usr/local/nagios/sbin/cmd.cgi">
	AuthType Digest
	AuthName "Restricted Nagios Command Access"
	AuthDigestProvider file
	AuthUserFile /usr/local/nagios/etc/htdigest.users
	Require user nagiosadmin
	</Directory>

This example restricts access to cmd.cgi to a single user (nagiosadmin). You can expand this to include a group (multiple users) or use Require valid-user, depending on your authentication strategy.

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Add instructions or link to TS section here for users who can't get Weblish to work when trying DirectoryMatchBlock.

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	This configuration enforces authentication and IP-based filtering for the Nagios command interface using a streamlined `<Files "cmd.cgi">` block. It's designed for clarity and ease of setup, especially for contributors who don't need group-based access or multi-realm authentication.
	The following `<Files "cmd.cgi">` block provides an example of a simplified, file-specific access control method designed for clarity with the Nagios command interface. It's ideal for contributors who prefer minimal setup or who are validating access to `cmd.cgi` directly.
	If you've already configured a broader `<DirectoryMatch>` block (e.g., for /usr/lib/nagios4/cgi-bin/`), this example acts as a targeted override. It streamlines authentication and IP filtering for just the command interface, and may require commenting out overlapping `Require ip` lines to avoid conflicts--especially if you're shifting access control to the file level or relying on firewall rules.

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	Allow from 127.0.0.1 <your-trusted-ip>
	Require from 127.0.0.1 <your-trusted-ip>

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This reflects the Apache 2.4+ syntax, which is default in both Debian 12 and Ubuntu 22.04.

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{{< caution >}}

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Replace <your-trusted-ip> with your actual IP address. Avoid hardcoding contributor IPs in PRs.

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{{< /caution >}}

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Removed the caution, it is redundant.

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	For advanced scenarios--such as managing access by user groups, supporting IPv6 ranges, or customizing multiple directory paths--refer to the full [Advanced Apache](#advanced-apache-configuration) configuration example below.
	For advanced scenarios--such as managing access by user groups, supporting IPv6 ranges, or customizing multiple directory paths--see the full [Advanced Apache Configuration](#advanced-apache-configuration) section below.

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	1. Restart Apache:
	Restart Apache:

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	Allow from 127.0.0.1 198.51.100.0
	Require from 127.0.0.1 198.51.100.0

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	<DirectoryMatch (/usr/share/nagios4/htdocs|/usr/lib/cgi-bin/nagios4|/etc/nagios4/stylesheets)>
	<DirectoryMatch "^(/usr/share/nagios4/htdocs|/usr/lib/cgi-bin/nagios4|/etc/nagios4/stylesheets)">

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	Use this version if you need group-based access, IPv6 support, and broader directory matching across multiple Nagios paths.
	Use this version if you are managing group-based multi-access, enforcing IPv6 restrictions, or customizing Nagios interface paths. For simpler setups, refer to the basic configuration [Configure Apache Authentication](#configure-apache-authentication) section above.

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{{< note>}}

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	Restart the Apache service to apply changes:
	1. Restart the Apache service to apply changes:

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{{< /note >}}

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	1. Enable Apache Modules and Restart
	1. Validate and Enable Apache Modules then Restart

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---

Validate Apache configuration

sudo apachect1 configstest

---

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	Enable require modules:
	Enable required modules:

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	sudo a2enmod rewrite cgi auth_digest authz_groupfile
	sudo a2enmod rewrite
	sudo a2enmod cgi
	sudo a2enmod auth_digest
	sudo a2enmod authz_groupfile

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	1. Restart Apache:
	1. Restart Apache to apply changes:

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	If `configtest` returns anything other than `Syntax OK`, double-check your `<DirectoryMatch>` and `Require` directives for typos or misplaced quotes.

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	- Add new hosts by editing files in `/etc/nagios4/conf.d/`.
	- Add new hosts by editing configuration files in:
	`/etc/nagios4/conf.d/`
	- After making changes, validate your configuration before restarting:
	sudo nagios4 -v /etc/nagios4/nagios.cfg
	If errors appear, Nagios will point to the specific file and line number. Fix those *before* restarting.

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	- Restart Nagios after changes:
	- Restart Nagios after changes:

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	keywords: ['nagios', 'nagios Core','monitoring','debian 12','ubuntu 22.04', "server health", "nagios plugins']
	keywords: ["nagios", "nagios Core", "monitoring", "debian 12", "ubuntu 22.04", "server health", "nagios plugins"]