Red Hat Enterprise Linux 9 Resources -- Frequently Asked Questions

As of June 2024, Red Hat Enterprise Linux 9 (RHEL9) is the primary operating system used on desktop systems at Courant. Red Hat Enterprise Linux 9 is also predominantly used on the majority of the Courant Institute's computational resources. If you are curious which Red Hat Enterprise Linux release is currently installed on a Courant machine, then you can simply run "cat /etc/*release" from a terminal. 

The page and its content provide information regarding a variety of issues that our users may have with RHEL9.

Frequently Asked Questions Overview

The documentation provided on this page below will be heavily influenced by the feedback that you, the users, send us about your experiences using Red Hat 9.

If you have any questions, comments, or concerns at all -- no question is insignificant -- then please do not hesistate to reach out to helpdesk@cims.nyu.edu and let us know. Your feedback could very likely become a part of this documentation.

What is Red Hat Enterprise Linux 9? 

Created by Red Hat, Red Hat Enterprise Linux 9 ( or "RHEL9") is a commercial open-source Linux distribution, offerring additional Linux Kernel features, improved security performance, and a plethora of quality of life improvements. 

Can I just use my CentOS 7 Linux machine? 

Unfortunately, no. You can no longer use the CentOS 7 Linux operating system -- the former standard operating system at NYU Courant.

The decision to move away from CentOS 7 was not made due to any personal preferences, however this upgrade was mandated due to a lack of official support for CentOS 7 from its distributors. Ultimately, CentOS 7 Linux is no longer a viable option at NYU Courant, as CentOS 7 will be reaching its end of life on June 30th, 2024.

In order to properly maintain and follow security protocols at NYU Courant, we may no longer support defunct operating systems such as CentOS 7 Linux.

How can I change my RHEL9 Desktop Environment?

Making the change to a new Operating System can be a bit disorienting. You might have gotten used to things appearing or acting a certain way after having become familiar with our previous CentOS 7 Linux operating system.

While we can no longer offer the CentOS 7 desktop environment, members of the Courant community have a variety of desktop environments currently available to them on our Red Hat 9 Machines. By default, the desktop environment used on our RHEL9 Desktop machines is "GNOME Classic," a desktop environment that closely mirrors the standard desktop environment for our CentOS 7 machines. 

In order to change your Red Hat 9 Desktop Environment, enter your CIMS username at the login screen. After hitting the "enter" key, you will be prompted to enter your password. At this "password entry" screen, you may notice that a small gear icon has appeared on the bottom right hand corner of your screen. Click on this gear icon, and you can select which Desktop environment you would like to utilize after successfully logging in. 

Note that your last selected desktop environment will persist even if you login to another machine. 

Additionally, you can further customize and modify these desktop environments to better suit your specific computing means.

Right now, the "default" desktop environment for our Red Hat 9 Desktops is "GNOME Classic". 

For those seeking a desktop environment more similar to the CentOS 7 Desktop environment, we would recommend either the default "Gnome Classic" or "Cinammon" desktop environments.

Which Desktop Environments are available for use? 

As of September 2024, the following environments are available on our RHEL9 Desktops: 

  • Cinnamon
  • Cinnamon (Software Rendering)
  • Standard (X11 display server)
  • GNOME Classic 
  • Custom
  • Plasma (X11)
  • User script 

If there is an additional desktop environment that you would like to utilize but isn't listed here, then please feel free to reach out to helpdesk@cims.nyu.edu and let us know! 

How can I change the scale of the screen? 

Depending on the size of your desktop monitor, you may notice that the icons and text on your machine are perhaps too small, or difficult to read. To rectify such a problem, we would recommend changing the "Scale" value found in the "Display Settings" on your RHEL9 machine. 

The change your display settings, right-click anywhere on your Desktop, and select "Display Settings". This will open up the Settings application, specifically in the "Displays" section. From here, you can change the Resolution, Refresh Rate, and Scale of your Display. Changing the "Scale" percentage value will make everything either appear smaller or larger.

How can I use the "Extensions" application? 

For those wishing to further customize their Desktop environment, there exists an "Extensions" application. This application features an array of built in toggles that enables one to enable additional desktop features such as an always locked in dock, a hot bar for your multiple desktops, or even activate a System Monitor. 

While the Extensions application is always available no matter your current desktop environment, changes made in Extensions will only be implemented if one is using the "Standard (X11 display server)" desktop environment. 

To start using Extensions, click on the "Activities" button on the upper left hand corner of your desktop environment in order to pull up your "Dock". From here, you can either search for "Extensions" using the search bar at the top of the screen, or you can click on the right most icon in your Dock -- "Show Applications" -- before scrolling to the Extensions application. 

Once inside of the Extensions application, you can utilize the switches/toggles provided in order to quickly modify your Desktop environment. Additionally, you can use the "Tweaks" companion application for additional customization options. 

How can I change from Light Mode to Dark Mode?

In addition to changing your desktop environment on our RHEL9 machines, one has the option to further customize their desktop experience to better suit their needs. In order to change your desktop environment from Light Mode to Dark Mode, you can use the Gnome Tweaks application. 

Unfortunately, the ability to change your desktop theme from Light Mode to Dark Mode is not available in every desktop environment. The specific instructions for changing your desktop theme from Light Mode to Dark mode also varies depending on your current desktop environment. 

Changing from Light Mode to Dark Mode in Cinnamon

To change from Light Mode to Dark Mode when using the "Cinammon" desktop environment, please follow these steps: 

  1. Click on the "Menu" item on the bottom left hand corner of your Desktop screen in order to search for "System Settings" 
  2. Open "System Settings". Click on "Appearance" --> "Themes".
  3. In the "Themes" tab of "System Settings" you can modify the look of your Mouse Pointer, Applications, Icons, and/or Desktop. 
  4. Click on "Applications" and you will be presented with a variety of cosmetic options. From here you can select both a Light or Dark theme, as well as an overall color scheme for your itsms. 
  5. Click on "Desktop" and you will similarly be able to select a Light or Dark theme, along with an overall color scheme for the Desktop bar at the bottom of your screen. 
Changing from Light Mode to Dark Mode in GNOME Classic or Standard

To change from Light Mode to Dark Mode when using the default "GNOME Classic" or "Standard (X11 display server)" desktop environment, please follow these steps: 

  1. Click on "Activities" in the upper right hand corner of your screen to open your dock. Click on "Show Applications" in order to search for "Tweaks"
  2. Open "Tweaks". Click on the "Appearance" tab on the left hand side of the Tweaks window. 
  3. In this "Appearance" tab, you can adjust the appearance of your Applications, Cursor, Shell, and Icons under the "Themes" category. 
  4. Using the "Applications" drop down menu, you can select an overall light or dark scheme for your windows, in addition to an overall color scheme. An example of a Dark Theme would be "Mint-Y-Dark-Blue", for example. 
  5. Using the "Shell" drop down menu, you can select the overall color scheme of the "Shell" -- the bars at the top and bottom of your screen. Please note that in order to enable this "Shell" drop down menu, you must make sure that Extensions has been activated. To do so, open up the "Extensions" application, and make sure that the toggle right next to "Extensions" at the top of the window has been toggled on. From there, scroll down to "User Themes" and toggle it on as well. Incidentally, you can also change the Shell from Extensions by clicking on the little gear next to "User Themes" once it has been enabled. 

How can I activate the System Monitor? 

In the event that you are performing some high-level computing, or GPU-accelerated processing, you might be curious as to what computing resources are currently be uilitized on your machine. By using the System Monitor, you can observe your machine's Memory and CPU usage -- as well as GPU usage if you are utilizing a GPU-enabled device.

If you are using the Standard (X11 display server) desktop environment, then you can use the "Extensions" application to switch on the System Monitor. Once you activated the System Monitor in "Extensions", just click on the date at the top of your screen in order to observe System Monitor.

Please note that while "Extensions" are available in every desktop environment, the System Monitor will only be visible if you are using Standard (X11 display server). 

How can I change the displayed Date and Time to AM/PM? 

In order to change the Date/Time at the top of your screen from a 24-hour time to AM/PM, please follow these instructions: 

  1. Open the "Settings" application. 
  2. Scroll down and select the "Date & Time" category on the left-hand side of the "Settings" window. 
  3. In the "Time Format" section you can select either "AM/PM" or "24-hour"

How can I change my background photo? 

Please note that in order to change one's background photo, you must be using the Standard (X11 Display Server) desktop environment. 

When using your Linux Desktop, you may want to personalize your machine by changing your background photo -- also known as your Desktop image. 

While in the Standard (X11 Display Server) desktop environment, right-click on your background image. In the small menu that pops up, select "Change Background..." in order to open the Background menu from Settings. 

In this Background menu, you can either select from Red Hat 9's built-in background images, or add your own image by clicking on the "Add Picture..." button located in the upper right hand corner of this Background menu. After clicking on "Add Picture..." you can now select a picture from your files. When you have selected your ideal photo, click on "Open" in order to add this photo to your selectable background photos. If you click on this added photo from your selectable background photos, then your background image will be changed to it. 

How can I change my favorite applications? 

If you have the "Applications Menu" turned on in Extensions, you may notice that an "Applications" option has appeared at the top of your screen. If you click on "Applications", you will see every application currently installed on your machine, starting with a preset group called "Favorites". Likewise, if you have "Frippery Panel Favorites" turned on in Extensions, you may notice that a small row of application icons have been added to your screen. This group of icons is known as your "Favorites"

Now that we know what favorite applications are, the question remains: How does one change these favorite applications? 

Within Extensions, if you have "Dash to Dock" and/or "Dash to Panel" enabled, then you will see a dock appear onscreen. This dock has not only your favorites, but any actively-running applications that you are currently using. If you right-click on any actively running application, then select "Add to Favorites", then this application will be added to your favorite applications. Conversely, if you want to remove any application from your favorites, then right click on any "favorite" application in the Dock, and then click "Remove from Favorites".

Please note that you will not be able to right click on your favorites for adding/removal if they are displayed via the "Frippery Panel Favorites" toggle in the Extensions application.

I used to ssh with public-key authentication, but now it is no longer working?

You might have been using ssh to connect to the Courant network -- such as access.cims.nyu.edu -- for several years using public-key authentication, only to discover that your public-key is now no longer functioning. Understand that we have not only upgraded our Linux desktop machines to RHEL9, but also our Linux servers, such as access1 and access2.

While using public-key authentication is still a viable option on our RHEL9 servers, the requirements for an ssh public-key have changed. For example, our ssh servers now requires a minimum 2048-bit key length for RSA keys -- a change implemented for increased security. 

For additional information on how to properly generate an ssh public-key for authentication, as well as general questions regarding connecting to access, please refer to "Connecting to access using ssh keys" 

How can I activate the Minimize and Maximize buttons when using the Standard (X11 display server) desktop environment ?

In order to turn on the "Minimize" and "Maximize" buttons when using the Standard (X11 display server) desktop environment, first open the Tweaks application. Once inside the Tweaks application, select the "Window Titlebars" tab on the left hand side of the Tweaks window. Once you are inside of the "Window Titlebars" tab, you will notice a "Titlebar Buttons" header. Enable the Maximize and/or Minimize buttons by enabling their respective switches. Likewise, you can also determine the placement of these Maximize/Minimize buttons by using the "Placement" toggle that is also listed under the Titlebar Buttons section.

How can I reset my display settings? 

Depending on the changes you have made when customizing your Red Hat 9 desktop, you may want to just revert things back to their default display settings. 

In order to reset your display settings, first open up the Tweaks application. Once inside of the Tweaks menu, click on the three-lines symbol button -- colloquially known as the "hamburger button" -- located on the left hand size of the Tweaks menu. Click on "Reset to Defaults", and you will be asked if you want to "Reset all tweak settings to the original default state?" Click on OK, and your display environment should reset to its CIMS "standard issue" display settings. 

In the event that things are still not quite normal after clicking on "Reset to Defaults", then you might also have to disable any changes that you might have made using the Extensions application. In order to disable the Extensions application, first open up Extensions. At the top of the Extensions menu, to the immediate left of the spyglass-search button, you will see a blue toggle. If you click on this blue toggle, it will turn grey, indicating that all of your Extensions have been turned off. In order to reactivate your Extensions customizations, just click on this grey toggle, turning it blue and re-enabling your Extensions settings.