Commenting out / uncommenting a line in a Debian configuration file

Like all operating systems such as UNIX, Linux stores the initial / standard settings and configuration parameters for its programs in the form of configuration files. These files are used to configure software applications, server processes, and operating system settings for your system. As a Linux administrator, you can edit these files in several ways; one of them is to comment or not to comment on the configuration line.

When you open the configuration file, you can see one or more lines starting with the “#” symbol, which means that the line is commented out. When the interpreter reads the contents of the configuration file, it ignores lines starting with the “#” character. Therefore, any line that activates a commented-out function means that the corresponding function is disabled on your system.

Here’s what the included (uncommented) function looks like in the configuration file

# This is an enabled feature

FeatureEnable= true

Here’s what a disabled (commented out) function looks like in a configuration file:

# This is a disabled feature

#FeatureEnable = true

In this article, we will provide an example and see how commenting and uncommenting lines or more can be used to enable or disable functions on your Linux system. We will run this example on the Debian 10 Buster system to enable automatic login for the user through the daemon.conf file located in / etc / gdm3 /

Example: Enabling Automatic Login for a Debian User

Let’s take this annotation and uncomment feature to enable automatic user login to Debian.

Open the Debian terminal through a search in the Application Launcher as follows:

Open daemon.conf file in the Nano editor using the following command:

$ sudo nano /etc/gdm3/daemon.conf

Please note that you must be superuser to edit most system configurations.

When you enter your password, the following file will open:

Change configuration file



You can see that the highlighted lines have been commented out. This means that the automatic login feature for user1 is disabled.

You can simply remove the # character from the last two lines we selected and specify the username instead of the “user1” value for the user whose automatic login you want to enable. For example:

Configuration File Section Included

You can see the color change of the included function.

Now save the file by clicking Ctrl + X and then Y,

Now, when you restart your computer, you will log in without asking for authentication information.

We saw how to uncomment a line to include a function or function. You can disable the function in the same way by adding the # character at the beginning of the line that defines the function.

Commenting out / uncommenting a line in a Debian configuration file