To remove the ACLs and the accompanying plus sign from a file or directory in linux

 

In Linux, a plus sign (+) at the end of the file permissions (e.g., -rwxrwxrwx+) indicates that the file or directory has extended permissions set through Access Control Lists (ACLs).

To remove the ACLs and the accompanying plus sign from a file or directory, you can use the setfacl command:

1. Remove all ACL entries: This will eliminate all extended ACLs associated with the file or directory.

   bash
   setfacl -b filename
   

   Replace filename with the name of your file or directory.

2. Remove the ACL mask: Sometimes, even after removing all ACL entries, the plus sign may persist due to an existing ACL mask. To remove it, use:

   bash
   setfacl -n filename
   

   Combining both steps ensures that all ACL entries and masks are removed:

   bash
   setfacl -bn filename
   

   This command removes all ACL entries and the ACL mask simultaneously, effectively clearing any extended permissions.

Note: After performing these operations, it's advisable to verify the current permissions using ls -l filename to ensure that the ACLs have been successfully removed and that the plus sign no longer appears.

Caution: Modifying ACLs can impact access permissions for users and groups. Ensure that the standard Unix permissions (rwx for user, group, and others) are set appropriately to maintain the desired access controls after removing ACLs.

By following these steps, you can remove the plus sign from the file permissions, indicating that no extended ACLs are set on the file or directory.

Dot at the end of Linux file permissions - How to Remove them

In Linux, when you list files using the ls -l command, a trailing dot (.) at the end of the permission string indicates that the file has an SELinux security context associated with it. This dot signifies that SELinux attributes are present, even if SELinux is disabled on the system.

To remove this trailing dot, you need to clear the SELinux security context from the files. This can be achieved using the setfattr command, which allows you to manipulate extended attributes on filesystem objects. Here's how you can do it:

1. Remove SELinux attribute from a single file or directory:

   bash
   sudo setfattr -h -x security.selinux /path/to/file_or_directory
   

   Replace /path/to/file_or_directory with the actual path of your file or directory.

2. Remove SELinux attributes recursively from a directory and its contents:

   bash
   find /path/to/directory -exec sudo setfattr -h -x security.selinux {} \;
   

   This command will traverse through the specified directory and remove the SELinux security context from all files and subdirectories within it.

Caution: Modifying or removing SELinux security contexts can have security implications. Ensure that you understand the consequences and have appropriate backups before making these changes.

After performing these steps, the trailing dot should no longer appear in the file permissions when you list them using ls -l

Multi-Factor Authentication for Red Hat Enterprise Linux (RHEL) 9

Microsoft does not provide a native version of the Microsoft Authenticator application for Red Hat Enterprise Linux (RHEL) 9 or any other Linux distribution. However, you can implement multi-factor authentication (MFA) on your RHEL 9 system using alternative methods that are compatible with standard authenticator apps, including Microsoft Authenticator.

Option 1: Using the Google Authenticator PAM Module

The Google Authenticator Pluggable Authentication Module (PAM) allows you to set up time-based one-time password (TOTP) authentication on your Linux system. These TOTP codes can be generated by various authenticator apps, including Microsoft Authenticator. Here's how to set it up:

1. Install the Google Authenticator PAM Module:

   First, ensure that the Extra Packages for Enterprise Linux (EPEL) repository is enabled:

   bash
   sudo dnf install epel-release
   

   Then, install the google-authenticator package:

   bash
   sudo dnf install google-authenticator
   

2. Configure the Google Authenticator for Your User Account:

   Run the following command to set up Google Authenticator for your user account:

   bash
   google-authenticator
   

   You'll be prompted with a series of questions. It's generally safe to answer 'yes' (y) to each prompt. This process will generate a QR code and a secret key.

3. Set Up the Authenticator App:

   Open the Microsoft Authenticator app on your smartphone, select the option to add a new account, and choose the "Other" account type. Scan the QR code displayed during the google-authenticator setup or manually enter the secret key.

4. Configure SSH to Require MFA:

   To enforce MFA for SSH logins, you'll need to modify the PAM and SSH configurations:

   • Edit the PAM Configuration for SSH:

     Open the SSH PAM configuration file:

     bash
     sudo nano /etc/pam.d/sshd
     

     Add the following line at the end of the file:

     swift
     auth required pam_google_authenticator.so nullok
     

     The nullok option allows users who haven't set up MFA to log in without it. Remove this option to enforce MFA for all users.

   • Modify the SSH Daemon Configuration:

     Edit the SSH daemon configuration file:

     bash
     sudo nano /etc/ssh/sshd_config
     

     Ensure the following settings are configured:

     nginx
     ChallengeResponseAuthentication yes
     AuthenticationMethods publickey,keyboard-interactive
     

     These settings enable challenge-response authentication and require both public key and MFA for login.

   • Restart the SSH Service:

     Apply the changes by restarting the SSH service:

     bash
     sudo systemctl restart sshd
     

For a detailed guide on setting up MFA using the Google Authenticator PAM module, refer to Red Hat's official documentation.

Red Hat

Option 2: Using the Authenticator Application via Snap

An alternative is to install the "Authenticator" application, which is available as a Snap package and can manage TOTP tokens. Here's how to install it:

1. Enable Snap Support on RHEL 9:

   Ensure that the EPEL repository is enabled:

   bash
   sudo dnf install epel-release
   

   Install Snapd:

   bash
   sudo dnf install snapd
   

   Enable and start the Snapd service:

   bash
   sudo systemctl enable --now snapd.socket
   

   Create a symbolic link to enable classic Snap support:

   bash
   sudo ln -s /var/lib/snapd/snap /snap
   

   Restart your system or log out and back in to ensure the Snap paths are updated.

2. Install the Authenticator Application:

   Install the Authenticator app using Snap:

   bash
   sudo snap install authenticator --edge
   

This application can generate TOTP codes compatible with services that support standard authenticator apps.

Snapcraft

Note: The availability and compatibility of these methods may vary depending on your organization's security policies and the specific services you're accessing. Always ensure that any changes to authentication mechanisms comply with your organization's security guidelines.