NethServer is highly modular: at the end of the installation a bare minimum set of features like network configuration and log viewer is installed. The Software center page allows the administrator to select and install additional modules, and also list and update the already installed software packages.
A module is usually constituted by multiple packages. It extends the system functionality. For instance a module can transform NethServer into an Email server, or a Web proxy.
A software package is an atomic unit of software. It is published by a public software repository. NethServer packages are files in the RPM  file format. Thus within this context the terms package and RPM can be used as synonyms.
A NethServer 7 system receives updates from different software projects:
Each project releases software updates according to its specific rules and development cycle, but all of them prefer software stability over bleeding edge features.
Updates released by the CentOS project are immediately available on NethServer directly from the CentOS mirrors. More info about CentOS updates:
Updates released by EPEL are available only if the unlocked software updates origin is selected, as explained below.
Even if the above projects strive for software stability, care is necessary to check if the updates fit well together. Every time the system is going to be updated, create a backup of the data and review the updates changelog to understand what is going to happen. If possible, test the updates in a non-production system. For any doubt ask the NethServer community forum! 
Every day an automated scheduled task checks if a new distribution release of CentOS is available; when this happens it sends an email notification message to the system administrator and changes the Software updates origin. The system administrator can temporarily change the software updates origin from Software center > Configure. The available choices are:
The Software center considers updates from all available software repositories. It ensures every installed package is at its latest version.
The “unlocked” origin is automatically selected by the system upgrade procedure that can be started only by the system administrator.
The Software center prevents to install the updates coming from a CentOS release different than the current system version. For example, it prevents to install updates from CentOS 7.6 if NethServer version is 7.5. Packages from other repositories which are generically compatible with “7” (like EPEL) are considered only when new modules are installed; once they have been installed they are never updated.
The “locked” origin is automatically selected when a new CentOS distribution release is available. When also the NethServer project releases a new version, the Software center asks to start the system upgrade. The upgrade procedure switches to the “unlocked” origin at the end.
yumis run from the command line and the software origin is “locked”, EPEL and other repositories which are generically compatible with “7” are enabled
Manual update procedure¶
When updates are available, a warning message appears in the Software center page.
Updates for the installed software are listed under the Updates tab. Further details about them are available under Updates CHANGELOG.
To start the system update click the Download and install button.
Regularly update the installed software to fix bugs, security issues and receive new features
Automatic update procedure¶
It is possible to perform some automatic actions when new software updates are available.
- Download and (optionally) install the updates
- Send an email to the system administrator (root) and to an additional list of recipients
The updates availability is checked by a task that runs at a random time overnight.
If the notification email is not delivered or is marked as spam, it is possible to configure a smarthost
The Available tab lists all of the modules that can be installed. This list can be filtered by category. See also Additional languages.
To install a module, check the corresponding box and click on Add. Some modules suggest optional packages that can be installed also at a later time.
Once a module has been installed, it is listed under the Installed tab.
To install optional packages at a later time, select Installed tab and push the Edit button on a listed entry.
To remove a module, go to the Installed tab and push the corresponding Remove button.
When removing a module other modules could be removed, too! Read carefully the list of affected packages to avoid removing required features.
List of installed packages¶
The complete list of installed RPM packages is available under Installed > Packages.
The section Installed software displays all packages already installed into the system with the full package version.
The Server Manager allows selecting the interface language at the login screen. Only installed languages are listed.
In Available tab, select the Languages category and install the desired languages.
|||RPM Package Manager – http://rpm.org|
|||NethServer – http://www.nethserver.org|
|||CentOS – Community ENTerprise Operating System https://www.centos.org/|
|||EPEL – Extra Packages for Enterprise Linux https://fedoraproject.org/wiki/EPEL|
|||(1, 2) NethServer community forum – http://community.nethserver.org|