CompTIA Updated XK0-005 Exam Questions and Answers by amaia

The command pam_tally2 -u joe -r will resolve the issue of Joe being unable to log in to the Linux system. The pam_tally2 command is a tool for managing the login counter for the PAM (Pluggable Authentication Modules) system. PAM is a framework for managing authentication and authorization on Linux systems. PAM allows the administrator to define the rules and policies for accessing various system resources and services, such as login, sudo, ssh, or cron. PAM also supports different types of authentication methods, such as passwords, tokens, biometrics, or smart cards. PAM can be used to implement login restrictions, such as limiting the number of failed login attempts, locking the account after a certain number of failures, or enforcing a minimum or maximum time between login attempts. The pam_tally2 command can display, reset, or unlock the login counter for the users or hosts. The -u joe option specifies the user name that the command should apply to. The -r option resets the login counter for the user. The command pam_tally2 -u joe -r will reset the login counter for Joe, which will unlock his account and allow him to log in to the Linux system. This will resolve the issue of Joe being unable to log in to the Linux system. This is the correct command to use to resolve the issue. The other options are incorrect because they either do not unlock the account (usermod -s /bin/bash joe or passwd -u joe) or do not affect the login counter (chage -E 90 joe). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Implementing Basic Security, page 517.

The reason the developer cannot log in is because their account is locked. This is indicated by the "!!" in the /etc/shadow file:

developer:!!::0:99999:7:::

The "!!" in the password field means the account is locked, and the user cannot authenticate using a password.

To unlock the account, the administrator must reset the password:

passwd developer

OR, if SSH key authentication is used, the administrator can remove the lock without setting a password:

usermod -U developer

Why the other options are incorrect?

A. The developer’s private key has been deleted from the server. → Incorrect, because the login attempt is failing before key authentication even starts.

C. The developer's public key is in the wrong location. → Incorrect, because the SSH configuration (PubkeyAuthentication yes) allows key-based authentication, but the user is still unable to log in. The issue is with the account lock.

D. SSH has been disabled for user log-in. → Incorrect, because PasswordAuthentication yes confirms SSH is enabled for users (except root).

References:

CompTIA Linux+ Official Documentation

Linux User Management – Red Hat

To create a symlink for /usr/local/bin/app-a, which was installed in /usr/local/share/app-a, the administrator can use the command ln -s /usr/local/share/app-a /usr/local/bin/app-a (A). This will create a symbolic link named /usr/local/bin/app-a that points to the original file /usr/local/share/app-a. The other commands will not create a symlink, but either move, copy, or synchronize the file. References:

[CompTIA Linux+ Study Guide], Chapter 3: Working with Files, Section: Creating Links

[How to Create Symbolic Links in Linux]

The error indicates that SELinux is preventing Apache from connecting to the database. The command setsebool -F httpd_can_network_connect_db on allows the Apache web server to make network connections to the database, resolving the permission denied error without disabling SELinux entirely.