LPI 202-450 Linux Professional Institute Exam Practice Test

Samba cannot use /etc/passwd and /etc/shadow directly because they store passwords in a different format than CIFS. CIFS passwords are encrypted using a one-way hash function, while Unix passwords are encrypted using a two-way cipher. Therefore, Samba needs a separate password file that stores the CIFS passwords in a compatible format. This file is usually called smbpasswd and can be created or updated using the smbpasswd command123 References:

• Chapter 9. Users and Security - Samba
• smbpasswd - Samba
• Chapter 20. samba authentication - linux-training.be

Chapter 9. Users and Security - Samba3

Chapter 9. Users and Security - Samba

 The unknown-clients statement in the ISC DHCPD configuration is used to specify whether or not an address pool can be used by nodes which have a corresponding host section in the configuration. A host section is a declaration that defines a static IP address for a specific client based on its MAC address or other identifier. An unknown client is a client that does not have a host section. The unknown-clients statement can be either allow, deny, or ignore, and it can be applied to a pool, a subnet, or a shared-network. For example, the following configuration allows unknown clients to use the pool of addresses from 192.168.1.100 to 192.168.1.200, but denies them from using the pool of addresses from 192.168.1.201 to 192.168.1.254:

subnet 192.168.1.0 netmask 255.255.255.0 { pool { range 192.168.1.100 192.168.1.200; allow unknown-clients; } pool { range 192.168.1.201 192.168.1.254; deny unknown-clients; } }

References:

• ISC DHCP 4.4 Manual Pages - dhcpd.conf: The official documentation of ISC DHCPD on how to configure the dhcpd.conf file, which includes the description of the unknown-clients statement and examples.
• How To Configure a DHCP Server on Ubuntu 20.04 | DigitalOcean: A tutorial from DigitalOcean on how to configure a DHCP server on Ubuntu 20.04, which includes the use of the unknown-clients statement and host sections.

 The sender_canonical_maps parameter on a Postfix server specifies an optional address mapping that applies when mail is delivered (sent) from the server. This mapping can be used to rewrite the sender address of outgoing messages to a different format or domain. For example, the following sender_canonical_maps entry will rewrite the sender address from user@localdomain to user@example.com:

user@localdomain user@example.com

The sender_canonical_maps parameter only affects the sender address and not the recipient address. The recipient address can be modified by other parameters such as recipient_canonical_maps or virtual_alias_maps.

References: You can learn more about sender_canonical_maps and other Postfix address rewriting parameters from the following sources:

• Postfix Address Rewriting
• Postfix Configuration Parameters
• Postfix Generic Mapping for Outgoing SMTP Mail

DNSSEC adds digital signatures to DNS records, which can be verified by the clients using public keys. This way, DNSSEC ensures that the DNS responses are authentic and have not been tampered with by attackers. DNSSEC does not encrypt DNS queries or answers, nor does it authenticate the user or the nameserver123

What is DNSSEC on DNS Server in Windows Server?1

How DNSSEC Works | Cloudflare

 The line A is valid in a configuration file in /etc/pam.d/ because it follows the correct syntax and semantics of a PAM configuration file. The syntax of a PAM configuration file is:

module_interface control_flag module_name module_arguments

The module_interface specifies the type of authentication action that the module can perform. There are four types of module interface: auth, account, password, and session. The control_flag specifies how important the success or failure of the module is to the overall authentication process. There are four types of control flag: required, requisite, sufficient, and optional. The module_name specifies the name of the library that contains the module. The module_arguments are optional parameters that can modify the behavior of the module.

The line A has the following components:

• module_interface: auth, which means the module is used for user authentication.
• control_flag: required, which means the module must succeed for authentication to continue. If the module fails, the failure is recorded and the rest of the modules are executed.
• module_name: pam_unix.so, which means the module is the standard Unix authentication module that verifies the user’s password against the /etc/passwd and /etc/shadow files.
• module_arguments: try_first_pass nullok, which means the module tries to use the password that was previously entered by the user (if any), and allows users with empty passwords to log in.

The line B is invalid because it has the wrong order of the fields. The control_flag should come before the module_name, not after. The line C is invalid because it uses parentheses and colons instead of spaces to separate the fields. The line D is invalid because it has the wrong syntax for the control_flag. The control_flag should be a single word, not a word in parentheses.

The standard port used by OpenVPN is 1194. OpenVPN is a VPN daemon that supports SSL/TLS security, ethernet bridging, TCP or UDP tunnel transport, and other features. OpenVPN can be configured to listen on any port, but the default port is 1194, which is registered with the IANA for OpenVPN. The port number can be specified in the OpenVPN configuration file using the port directive. For example:

port 1194

This will instruct OpenVPN to listen on port 1194. The port number must match on both the server and the client sides of the connection. The port number can also be specified as an argument to the openvpn command. For example:

openvpn --port 1194

This will run OpenVPN with port 1194 as the default port.

References:

• Reference Manual For OpenVPN 2.6 | OpenVPN
• Reference Manual For OpenVPN 2.0 | OpenVPN
• Which ports to open for VPN PPTP, L2TP, IPsec, OpenVPN and … - ITIGIC

According to the configuration, the postmaster address is set to postmaster@domain.com. This means that any system-generated messages or notifications sent to the administrator of this domain will use this address as the sender. The postmaster address is also used to receive messages from external senders who need to contact the administrator for any reason, such as reporting spam or abuse. The postmaster address is a mandatory requirement for any mail server, as specified by the RFC 5321 standard. References:

• LPIC-2 exam 202 objectives, topic 207.3, Manage the postfix mail system
• RFC 5321, section 4.5.1, Postmaster Role

 OpenVAS is a network security scanner project that, at the core, is a server with a set of network vulnerability tests (NVTs) to detect security problems in remote systems and applications. It is an open-source tool that was forked from Nessus, a popular commercial scanner. OpenVAS can perform comprehensive scans of networks and hosts, as well as web application scanning and compliance testing. It also provides a graphical user interface (GUI) and a command-line interface (CLI) for managing scans and reports. References:

• Greenbone Vulnerability Management - Gentoo wiki
• The Best Network Vulnerability Scanners Tested in 2023 - Comparitech

 The Dovecot configuration variable that specifies the location of user mail is mail_location. This variable defines the format and path of the mailboxes, and it can be overridden by userdb or namespace settings. The format of the mail_location specification is:

:[:=[:=...]]

where  is one of the supported mailbox formats, such as mbox, maildir, or dbox;  is the absolute path to the mail directory; and = are optional parameters that modify the behavior of the mailbox format.

For example, a mail_location setting for maildir format could look like this:

mail_location = maildir:~/Maildir

This means that the user’s mail is stored in the Maildir subdirectory of their home directory.

References: You can find more information about the mail_location variable and its parameters in the following resources:

• Mail Location Settings — Dovecot documentation
• Config Variables — Dovecot documentation

The option for BIND that is required in the global options to disable recursive queries on the DNS server by default is recursion no;. This option tells the server not to provide recursive query behavior to any client, unless overridden by a view or a zone statement. Recursive queries are queries that the server will try to resolve by contacting other servers if it does not have the answer in its cache or zones. Disabling recursive queries can improve the security and performance of the server, especially if it is only meant to serve authoritative zones123 References:

• BIND: Stop Recursion DNS Under Linux / UNIX - nixCraft
• How to Disable External DNS Recursion in BIND? | DeviceTests
• bind - How to Disable External DNS recursion? - Ask Ubuntu

The client-to-client option in OpenVPN enables the VPN server to forward packets between VPN clients internally, without sending them to the IP layer of the host system. This means that the host networking stack does not see or process the client-to-client traffic at all. This option can improve the performance and efficiency of the VPN, as well as reduce the load on the host system. However, it also means that the VPN server cannot apply any firewall rules or routing policies to the client-to-client traffic, as it would if the traffic passed through the host IP layer. Therefore, this option should be used with caution and only when the VPN clients are trusted and isolated from other networks. References:

• OpenVPN 2.x HOWTO, section “Client-to-client”
• OpenVPN 2.4 man page, option “–client-to-client”

 The nmap command is a network exploration and security auditing tool that can scan hosts and networks for open ports, services, operating systems, vulnerabilities, and other information. The nmap parameters that can scan a target for open TCP ports are:

• -sT: This parameter performs a TCP connect scan, which establishes a complete connection to the target host by completing a TCP three-way handshake. This is the default scan type when the user does not have root privileges. The advantage of this scan is that it works on any system that supports TCP, but the disadvantage is that it is easily detectable by firewalls and intrusion detection systems.
• -sS: This parameter performs a TCP SYN scan, which sends a TCP SYN packet to the target port and waits for a response. If the response is a SYN/ACK packet, the port is open. If the response is a RST packet, the port is closed. This scan does not complete the TCP three-way handshake, so it is faster and stealthier than the TCP connect scan. However, this scan requires root privileges and may not work on some systems that do not follow the TCP standard.

The other parameters are not related to TCP port scanning:

• -sO: This parameter performs an IP protocol scan, which sends IP packets with the specified protocol number set in the IP header. It can be used to determine which IP protocols are supported by the target host.
• -sZ: This parameter is not a valid nmap parameter and will cause an error.
• -sU: This parameter performs a UDP scan, which sends a UDP packet to the target port and waits for a response. If the response is an ICMP port unreachable message, the port is closed. If the response is a UDP packet, the port is open. This scan can be used to find open UDP ports, which are often used by DNS, SNMP, DHCP, and other services.

References: LPIC-2 202 exam objectives, LPIC-2 202-450 Exam Prep: Network Configuration, Nmap Tutorial: Common Commands, Nmap Scan Types

Cybersecurity | Nmap | TCP Connect Scan | Codecademy

The command in the question is using the ldapsearch tool to query an LDAP directory. The filter expression is (|(cn=marie)(!(telephoneNumber=9*))), which means to match entries that satisfy either one of the two conditions inside the parentheses. The first condition is (cn=marie), which means the common name attribute (cn) of the entry is equal to marie. The second condition is (!(telephoneNumber=9*)), which means the telephone number attribute (telephoneNumber) of the entry is not equal to 9 followed by any number of characters. The ! operator means logical negation, and the * operator means wildcard matching. Therefore, the command will return entries that have a cn of marie or don’t have a telephoneNumber beginning with 9. References: LPIC-2 202 exam objectives, LDAP Search Filters

The verbose_proctitle parameter in the Dovecot configuration file controls whether Dovecot adds extra information to its process titles. When this parameter is set to yes, Dovecot will show the username, IP address of the peer, and the connection status for each process. This can help to associate the processes with users and peers, and to monitor the activity of the mail server. For example, the process titles may look like this:

dovecot/imap-login user@domain.com [192.168.0.1] dovecot/imap user@domain.com [192.168.0.1] IDLE

The verbose_proctitle parameter can be set in the /etc/dovecot/dovecot.conf file or in the /etc/dovecot/conf.d/10-master.conf file. The default value is no, which means that Dovecot will only show the process name and the command state. For example:

dovecot/imap-login dovecot/imap [idling]

The other options are not related to the process titles. The --with-linux-extprocnames option for ./configure when building Dovecot is not a valid option. The sys.ps.allow_descriptions and proc.all.show_status parameters in sysctl.conf or /proc are not valid parameters. The process_format parameter in the Dovecot configuration is used to specify the format of the process name, not the process title.

References:

• LPIC-2 Exam 202 Objectives, Objective 205.4: Managing a dovecot server
• Process Titles — Dovecot documentation, Dovecot Documentation
• Dovecot Configuration Parameters: verbose_proctitle, Dovecot Documentation
• Dovecot Configuration Parameters: process_name, Dovecot Documentation
• How to monitor dovecot processes? - Server Fault, Forum

The command that creates a SSH key pair is ssh-keygen. This command generates a public and a private key file that can be used for SSH authentication. The command can take various options to specify the algorithm, the file name, the passphrase, and other parameters for the key pair. For more information, see the web search results below or the man page of ssh-keygen.

How to Use ssh-keygen to Generate a New SSH Key?

The pam_nologin module is used to prevent users from logging into the system when the /etc/nologin file exists. The file can contain a message that is displayed to the user before the login is denied. The only exception is the root user, who can always log in regardless of the existence of the /etc/nologin file. This method is useful for system maintenance or emergency situations when normal users should not access the system. References: LPIC-2 exam 201 topics, pam_nologin man page

The http_access directive for Squid allows or denies access to the web resources based on defined access control lists (ACLs). The syntax of the http_access directive is:

http_access allow|deny [!]aclname …

The directive takes one or more ACL names as arguments, separated by spaces. The first argument is either allow or deny, indicating the action to be taken if the ACLs match. The optional ! character before an ACL name negates the result of that ACL.

To allow users in the ACL named sales_net to only access the Internet at times specified in the time_acl named sales_time, the correct http_access directive is:

http_access allow sales_net sales_time

This directive means that if the client IP address matches the sales_net ACL and the request time matches the sales_time ACL, then the access is allowed. Otherwise, the access is denied or the next http_access directive is evaluated.

The LDIF excerpt shows the distinguished name (dn) of Robert Smith as “cn=Robert Smith, ou=people, dc=example, dc=com”. The organizational unit (ou) attribute is used to represent an organizational unit in which an entry resides. In this case, Robert Smith is part of the “people” organizational unit.

References:

• [OpenLDAP Software 2.6 Administrator’s Guide: The LDIF File Format]: The official documentation of OpenLDAP on the LDIF file format, which explains the syntax and structure of LDIF entries and attributes.
• [LDAP Data Interchange Format (LDIF) - Version 1]: The RFC 2849 document that defines the LDAP Data Interchange Format (LDIF), which is a common format for exchanging LDAP data.

The .htaccess file in the directory is configured to require a valid user. The .htpasswd file contains the username and password for usera. Therefore, usera can access the site using the password s3cr3t. References:

• LPIC-2 Overview
• LPIC-2 202-450
• Password Protecting Your Pages with htaccess

 DHCPv6 supports three types of IPv6 address assignments:

• Individual address assignment (IA_NA): This is the stateful mode of DHCPv6, where the DHCPv6 server assigns a normal IPv6 address to a client that can be renewed or released. The address is chosen from a pool of prefixes configured on the server and is unique and non-duplicate. The client can request one or more addresses using the IA_NA option in the DHCPv6 messages1
• Temporary address assignment (IA_TA): This is similar to the IA_NA mode, but the addresses assigned are temporary and cannot be renewed or released. The temporary addresses are used for privacy reasons and are generated by the client using a random interface identifier. The client can request one or more temporary addresses using the IA_TA option in the DHCPv6 messages2
• Prefix delegation (IA_PD): This is the mode where the DHCPv6 server delegates a whole IPv6 prefix to a client, such as a router or a host, that can use it for further subnetting or routing. The client can request one or more prefixes using the IA_PD option in the DHCPv6 messages. The delegated prefixes are also chosen from a pool of prefixes configured on the server3

References: 1: IP Addressing: DHCP Configuration Guide - IPv6 Access Services: DHCPv6 Individual Address Assignment 2: RFC 4941 - Privacy Extensions for Stateless Address Autoconfiguration in IPv6 3: IP Addressing: DHCP Configuration Guide - IPv6 Access Services: DHCPv6 Prefix Delegation

Fail2ban is a tool that monitors the system logs for failed login attempts and blocks the offending IP addresses using netfilter rules. Netfilter is a framework that provides packet filtering, network address translation, and other functions for the Linux kernel. Fail2ban uses the iptables command to manipulate the netfilter rules and create chains of rules that match the source IP address of the attacker and drop or reject the packets from that IP address. Fail2ban can also use other firewall tools, such as firewalld or ufw, to create the netfilter rules. Fail2ban can block the IP addresses for a specified amount of time, or permanently, depending on the configuration. Fail2ban can protect various services, such as SSH, HTTP, FTP, etc., by creating different jails for each service. A jail is a set of parameters that define how to monitor a log file, how to detect a failed login attempt, how to ban an IP address, and how long to keep the ban.

Fail2ban does not block offending SSH clients by any of the other options. It does not act as a proxy in front of SSHD, nor does it modify the SSHD configuration. It does not create null routes that drop any answer packets sent to the client, nor does it modify the TCP Wrapper configuration for SSHD.

References:

• How To Protect SSH with Fail2Ban on Ubuntu 20.04
• How To Prevent SSH Brute Force Attacks Using Fail2ban In Linux
• Fail2ban - Wikipedia
• Fail2ban Manual

 TCP/IP stack fingerprinting is a technique that allows nmap to remotely detect the characteristics of a TCP/IP stack implementation on a target host. By sending a series of probes (such as TCP and UDP packets) and analyzing the responses, nmap can infer the operating system (OS) of the target host based on a database of known OS fingerprints. Each OS has a unique way of setting certain parameters and flags in the TCP/IP headers, such as the initial packet size, the initial TTL, the window size, the max segment size, the window scaling value, and the “don’t fragment”, “sackOK”, and “nop” flags. These values can be combined to form a signature or a fingerprint for the target host, which can then be compared to the nmap-os-db database that contains more than 2,600 OS fingerprints. If there is a match, nmap will print out the OS details, such as the name, the version, and the vendor. If there is no match, nmap will print out a message asking the user to submit the fingerprint to the nmap project for further analysis.

TCP/IP stack fingerprinting is useful for several purposes, such as network mapping, security auditing, vulnerability scanning, and penetration testing. By knowing the OS of the target host, nmap can tailor its scanning techniques and exploit the weaknesses of the specific OS. TCP/IP stack fingerprinting can also help identify rogue or unauthorized devices on a network, or detect OS spoofing attempts by the target host.

References:

• OS Detection | Nmap Network Scanning
• TCP/IP stack fingerprinting - Wikipedia
• Cybersecurity | Nmap | OS Detection | Codecademy

The doveadm who sub-command shows information about the currently connected users and their sessions. The output includes the following columns:

• user: The username of the connected user.
• ip: The IP address of the client.
• port: The port number of the client.
• service: The name of the Dovecot service, such as imap, pop3, lmtp, etc.
• protocol: The protocol version used by the client, such as IMAP4rev1, POP3, etc.
• pid: The process ID of the Dovecot process that handles the connection.
• type: The type of the connection, such as tcp, ssl, etc.
• state: The state of the connection, such as running, idle, etc.
• since: The time when the connection was established.

References:

• doveadm-who - Dovecot Wiki
• LPIC-2 exam 202 objectives, topic 211.3, “Managing Mailbox Access”

The sshd configuration file is used to customize the behavior of the SSH server daemon. Some of the lines in the file can affect the security of the server and should be modified accordingly. The following are two examples of such lines:

• Protocol 2, 1: This line specifies the SSH protocol versions that are supported by the server. The possible values are 1 and 2, where 1 is the older and less secure version and 2 is the newer and more secure version. The recommended value is 2, as it provides stronger encryption, authentication, and integrity mechanisms. Allowing protocol 1 can expose the server to various attacks, such as man-in-the-middle, replay, and insertion attacks. Therefore, this line should be changed to Protocol 2 or commented out (as protocol 2 is the default value).
• PermitRootLogin yes: This line determines whether root login is allowed on the server. The possible values are yes, no, prohibit-password, and without-password. The value yes allows root login with any authentication method, including password. This can pose a serious security risk, as root is the most privileged user on the system and can perform any action. If an attacker manages to guess or obtain the root password, they can gain full control over the server. Therefore, this line should be changed to no or prohibit-password (which allows root login only with public key authentication) or commented out (as no is the default value).

References: LPIC-2 202 exam objectives, LPIC-2 202-450 Exam Prep: Network Configuration, The Best Ways to Secure Your SSH Server, Configure the /etc/ssh/sshd_config file

Linux SSH Server (sshd) Configuration and Security Options With ...1

The Best Ways to Secure Your SSH Server - How-To Geek

The tool dig, which stands for domain information groper, is a command-line utility that provides the most information when performing DNS queries, without any options. Dig can query any type of DNS record and display the full response from the DNS server, including the header, question, answer, authority, and additional sections. Dig can also show the query time, server address, response code, flags, and statistics. Dig is a versatile and powerful tool that can be used for troubleshooting, testing, and debugging DNS issues123 References:

• dig(1) - Linux manual page
• How to Use the Dig Command on Linux
• How to use the dig command for DNS queries on Linux

 The Apache HTTPD configuration directive that specifies the RSA private key that was used in the generation of the SSL certificate for the server is SSLCertificateKeyFile1. This directive sets the file path and name of the file containing the server private key2. The private key is used to decrypt the data that is encrypted with the public key contained in the certificate1. The private key must match the certificate, otherwise an error will occur when starting the server2. The other options are not valid directives for Apache HTTPD. References:

• mod_ssl - Apache HTTP Server Version 2.4
• Why is SSLCertificateKeyFile needed for Apache? - Stack Overflow

 A route to the destination fe80::/10 will appear in the Linux routing table after activating IPv6 on a router’s network interface, even when no global IPv6 addresses have been assigned to the interface. This is because fe80::/10 is the prefix for link-local addresses in IPv6, which are automatically configured on any interface that supports IPv6. Link-local addresses are used for communication within the same link or subnet, and are not routable beyond the local network. Link-local addresses have the format fe80::interface identifier, where the interface identifier is usually derived from the MAC address of the interface. Link-local addresses are useful for purposes such as neighbor discovery, router advertisement, and address autoconfiguration. Every IPv6-enabled interface must have a link-local address, even if it also has other types of addresses.

The other options are not correct. 0::/128 is the unspecified address, which is used as a placeholder when no address is available. It is not a valid destination for a route. 0::/0 is the default route, which matches all destinations. It is not automatically added to the routing table when IPv6 is enabled on an interface. fe80::/64 is not a valid prefix for link-local addresses, as it is too specific. Link-local addresses use the prefix fe80::/10, which covers the range from fe80:: to febf::. 2000::/3 is the prefix for global unicast addresses, which are routable on the public Internet. They are not automatically configured on an interface, unless stateless address autoconfiguration (SLAAC) or DHCPv6 is used.

References:

• IPv6 Link-Local Addresses - PacketLife.net
• IPv6 Addressing and Basic Connectivity Configuration Guide, Cisco IOS XE Gibraltar 16.12.x - IPv6 Addressing [Cisco IOS XE 16] - Cisco
• IPv6 Addressing and Subnetting

 The ErrorLog directive of the Apache HTTPD server defines the location and name of the file where the server will log any errors it encounters. The default value of this directive is logs/error_log, which means that the error log file will be stored in the logs subdirectory of the server root directory. The ErrorLog directive can also accept a filename relative to the server root, an absolute filename, or a pipe to a program that will handle the logging. For example, ErrorLog logs/my_error_log will store the error log file in the logs subdirectory with the name my_error_log, ErrorLog /var/log/httpd/error_log will store the error log file in the /var/log/httpd directory with the name error_log, and ErrorLog “|bin/rotatelogs logs/error_log 86400” will pipe the error log to the rotatelogs program that will rotate the log file every 86400 seconds. References: Log Files - Apache HTTP Server Version 2.4, Directive Quick Reference - Apache HTTP Server Version 2.4, How do I find Apache http server log files? – Code A Site Blog, mod_log_config - Apache HTTP Server Version 2.2

The two commands shown in the image are used to drop packets with source or destination addresses from fe80::/64 in the FORWARD chain. The first command drops packets with source addresses from fe80::/64, while the second command drops packets with destination addresses from fe80::/64. Both commands will complete without an error message or warning because the affected network is not already part of another rule. The other statements are incorrect for the following reasons:

• B. The rules disable packet forwarding because network nodes always use addresses from fe80::/64 to identify routers in their routing tables. This is false because network nodes do not use link-local addresses to identify routers in their routing tables. Instead, they use global or unique local addresses that are advertised by routers through router advertisements or DHCPv6.
• C. ip6tables returns an error for the second command because the affected network is already part of another rule. This is false because there is no indication that the affected network is already part of another rule. Even if it was, ip6tables would not return an error, but rather append the new rule to the existing ones, unless the -I option was used to insert the new rule at a specific position.
• E. The rules suppress any automatic configuration through router advertisements or DHCPv6. This is false because the rules only affect the FORWARD chain, which is used to process packets that are routed through the router. The rules do not affect the INPUT or OUTPUT chains, which are used to process packets that are destined for or originated from the router. Therefore, the rules do not interfere with the router’s ability to send or receive router advertisements or DHCPv6 messages.

References: LPIC-2 202 exam objectives, LPIC-2 202-450 Exam Prep: Network Configuration, IPv6 Firewalling with ip6tables, IPv6 Addressing and Basic Connectivity

The option in named.conf that specifies which hosts are permitted to ask for domain name information from the server is allow-query. The allow-query option is used to define an access control list (ACL) that matches the source IP address of the DNS query. The ACL can be a list of IP addresses, networks, keywords, or predefined ACL names. The default value of allow-query is any, which means that any host can query the server. However, this can pose a security risk, as the server may be exposed to unwanted or malicious queries. Therefore, it is recommended to restrict the allow-query option to only the hosts that need to access the server, such as the local network or trusted clients. For example, the following option allows only the hosts in the 192.168.1.0/24 network and the localhost to query the server:

allow-query { 192.168.1.0/24; localhost; };

The other options are not valid in named.conf. allowed-hosts, accept-query, permit-query, and query-group are not recognized keywords by BIND.

References:

• LPIC-2 exam 202 objectives, topic 208.1, “Implementing a web server”
• BIND 9 Administrator Reference Manual, chapter 6, “Access Control Lists and TSIG”
• How to Configure DNS Server with TSIG on CentOS 8

The Samba service that handles the membership of a file server in an Active Directory domain is winbindd. Winbindd is a daemon that provides a number of services to the Name Service Switch (NSS) capability of the system, such as resolving user and group information from a Windows NT server and authentication. Winbindd can also be used to join a Samba file server to an Active Directory domain and authenticate domain users to access the file shares12 References:

• Chapter 4. Using Samba for Active Directory Integration Red Hat Enterprise Linux 7 - Red Hat Customer Portal
• Winbind: Use of Domain Accounts - SambaWiki

 The command that displays an overview of the Postfix queue content to help identify remote sites that are causing excessive mail traffic is qshape. This command shows the number of messages in the active, deferred, and hold queues, grouped by the next-hop domain name. It also shows the age distribution of the messages in each queue, which can help to identify domains that are slow or unreachable. The output of qshape looks like this:

The first column shows the next-hop domain name, or TOTAL for the sum of all domains. The second column shows the total number of messages in the queue for that domain. The remaining columns show the number of messages in different age ranges, in minutes. For example, the T column shows the number of messages that are less than 5 minutes old, the 5 column shows the number of messages that are between 5 and 10 minutes old, and so on. The last column shows the number of messages that are older than 1280 minutes (about 21 hours).

The qshape command can be used with different options to specify the queue name, the domain name pattern, the bucket size, the bucket count, the sort order, and the output format. For more information, see the qshape man page1.

References: You can find more information about the qshape command and its usage in the following resources:

• qshape - Postfix queue analysis tool
• Postfix Queue Management

 In the ISC DHCPD server configuration, to always assign the IP address 192.168.1.2 to a host with the MAC address 08:00:2b:4c:59:23, you need to create a host declaration within your dhcpd.conf file. Option A provides the correct syntax for this configuration:

This configuration ensures that whenever a DHCP request is received from the MAC address specified, the ISC DHCPD server will always assign it the IP address 192.168.1.2.

References:

• ISC DHCP 4.1 Manual Pages - dhcpd.conf: The official documentation of ISC DHCPD on how to configure the dhcpd.conf file, which includes the host declaration syntax and examples.
• isc-dhcp-server: Using option dhcp-client-identifier in host declaration to identify a client: A question and answer from Server Fault on how to use the option dhcp-client-identifier in a host declaration, which also shows the use of the hardware-ethernet and fixed-address parameters.

To fully disable password based logins for SSH, you need to set both Challenge Response Authentication and Password Authentication to no in the sshd configuration file. These options control whether the server will accept password-based authentication methods such as keyboard-interactive or PAM. Setting them to no will only allow public key authentication or other methods that do not involve passwords. References:

• LPIC-2 Exam 202 Objectives1
• LPIC-2 Exam 202 Study Guide2
• LPIC-2 Exam 202 Topic 208: SSH Configuration3

 This option enables Samba to synchronize the UNIX password with the SMB password when the encrypted SMB password in the passdb is changed using smbpasswd. This means that the user only needs to change their password once, and both the UNIX and SMB passwords will be updated. Samba will use the passwd program specified by the passwd program option to change the UNIX password. Samba will also follow the passwd chat option to communicate with the passwd program. The other options are either invalid or irrelevant for this question. References: 1, 2, 3