ssh-keygen -t rsa generates an RSA key pair.
ssh-copy-id -i ~/.ssh/id_rsa.pub john@server2 copies the public key to the remote server's authorized_keys, enabling passwordless login.

Package management troubleshooting is a critical Linux administration skill addressed in CompTIA Linux+ V8. After system patching, identifying which packages were installed, updated, or removed is often the first step in diagnosing application failures.
The dnf history command is specifically designed for this purpose. It displays a chronological list of all DNF transactions, including installations, upgrades, downgrades, and removals. Each transaction is assigned an ID and includes timestamps, affected packages, and actions taken. This allows administrators to correlate application failures with recent changes.
Option A is correct because it provides historical context rather than just current package state. Linux+ V8 documentation highlights dnf history as an essential auditing and rollback tool.
The other options are insufficient. dnf list shows installed or available packages but does not indicate when they were installed. dnf info displays metadata for a specific package but does not show transaction history.
dnf search is used to find packages by name or description.
By reviewing recent transactions with dnf history, administrators can quickly identify problematic updates and take corrective action, such as rolling back a package.
Therefore, the correct answer is A.

The SSH configuration option PermitRootLogin prohibit-password prevents the root user from logging in with password authentication. This setting means root cannot use a password to log in via SSH; only key- based authentication is permitted for root. The administrator can still log in as root locally, which is not affected by this SSH configuration. To allow SSH access as root, the administrator must use an SSH key instead of a password.
Other options:
A). MaxSessions controls the number of simultaneous SSH sessions but is not causing the login denial here.
B). PAM (Pluggable Authentication Modules) is disabled, but enabling it is not required for basic SSH authentication.
C). Changing the SSH port is unrelated to the authentication method issue.
Reference:
CompTIA Linux+ Study Guide: Exam XK0-006, Sybex, Chapter 11: " Securing Linux " , Section: " Securing SSH Access " CompTIA Linux+ XK0-006 Objectives, Domain 3.0: Security

System boot performance analysis is an important system management task included in Linux+ V8. When administrators need to determine how long services take to start during boot, systemd analysis tools are required.
The correct command is systemd-analyze blame. This command lists all systemd services and shows how long each one took to initialize during the boot process. It is commonly used to identify slow-starting services that may impact system startup performance, including NetworkManager.
The other options are incorrect. resolvectl is used for DNS resolution management and provides no service timing information. journalctl can display logs but does not provide a clear, summarized service startup timing report. systemctl daemon-reload only reloads systemd unit files and does not perform analysis.
Linux+ V8 documentation explicitly references systemd-analyze blame as the correct tool for diagnosing service startup delays. Therefore, the correct answer is D.

Directory services are a key part of enterprise Linux environments and are covered under the Security domain in Linux+ V8. The Lightweight Directory Access Protocol (LDAP) is specifically designed to access and manage distributed directory information.
LDAP directories store structured, hierarchical data such as users, groups, computers, and organizational units. Linux systems commonly use LDAP for centralized authentication, authorization, and identity management. LDAP is also the foundation for services like Active Directory and FreeIPA.
The other options are incorrect. SMB is a file and printer sharing protocol. TLS is an encryption protocol used to secure communications. Kerberos (KRB-5) is an authentication protocol often used alongside LDAP but does not store directory information itself.
Linux+ V8 documentation highlights LDAP as the primary protocol for directory-based identity services.
Therefore, the correct answer is C.