Correct:

B. htpasswd
htpasswd is the dedicated utility that comes with Apache HTTP Server for creating and managing flat-file password databases used for HTTP Basic and Digest authentication. These files (commonly named .htpasswd) store usernames and their encrypted passwords. Apache then uses these files, configured via directives like AuthUserFile, to authenticate users accessing protected areas of a website.
Incorrect:

A. htaccess

.htaccess (Hypertext Access) is a per-directory configuration file that Apache reads. It‘s used to enable and configure authentication within a specific directory (e.g., by setting AuthType, AuthName, and pointing to the AuthUserFile created by htpasswd). However, .htaccess itself is a configuration file, not a command used to create user accounts.
C. apache2ctl

apache2ctl (or apachectl on some systems) is a control script for the Apache HTTP Server. It‘s used to start, stop, restart, gracefully restart, or check the syntax of Apache‘s configuration files. It manages the Apache service but does not have functionality to create user authentication accounts.
D. passwd

passwd is a standard Linux command used to change a user‘s system password (i.e., the password stored in /etc/shadow). It is for local system users, not for HTTP authentication accounts managed by Apache.

Correct:

A. /var/httpd/luna/edu/index.htm
Explanation: The VirtualDocumentRoot directive with the %-2/%-1 format string is designed to extract parts of the hostname for directory mapping.

%0: The entire hostname (e.g., http://www.luna.edu)
%1: The first component of the hostname, counting from the right (e.g., edu)
%2: The second component of the hostname, counting from the right (e.g., luna)
%-1: The first component from the left, with hyphens removing components from the right (e.g., http://www.luna)
%-2: The second component from the left, with hyphens removing components from the right (e.g., luna)
Given http://www.luna.edu/index.htm, the hostname is http://www.luna.edu.

%-2 will resolve to luna.
%-1 will resolve to edu.
Therefore, VirtualDocumentRoot /var/httpd/%-2/%-1 translates to /var/httpd/luna/edu.

The requested file /index.htm is then appended, resulting in /var/httpd/luna/edu/index.htm.

Incorrect:

B. /var/httpd/www/luna/index.htm

This implies www would be % -2 and luna would be % -1, which is incorrect for the %-N format that counts from the right and removes components from the left.
C. /var/httpd/luna/www/index.htm

This structure does not align with how %-2 and %-1 extract components from http://www.luna.edu.
D. /var/httpd/www/luna/edu/index.htm

This includes www which is not accounted for by %-2/%-1 when the hostname is http://www.luna.edu. The www is effectively ignored by this specific VirtualDocumentRoot pattern.

Correct:

A. htpasswd /srv/www/security/site-passwd user
This is the correct command for changing the password of an existing user in an htpasswd file. When htpasswd is invoked with just the file path and the username, it will prompt for a new password and update the entry for that user in the specified site-passwd file. It modifies the existing entry without recreating the file or deleting other users.
Incorrect:

B. NDA

“NDA“ (Non-Disclosure Agreement) is irrelevant to a Linux command-line question. This option is a distractor.
C. htpasswd -n /srv/www/security/site-passwd user

The -n option with htpasswd is used to print the encrypted password to standard output without updating the file. While useful for creating scripts or adding entries manually, it does not change the password in the file directly.
D. htpasswd -c /srv/www/security/site passwd user

The -c option with htpasswd is used to create a new password file. If the file already exists, using -c will overwrite it, deleting all existing users and their passwords. This would result in data loss for other users in the site-passwd file, which contradicts the “without losing data“ requirement of the question.
E. htpasswd -D /srv/www/security/site-passwd user

The -D option with htpasswd is used to delete a user from the password file. This is the opposite of changing a password and would also result in data loss (the user‘s entry is removed).

Correct:

B. htpasswd
htpasswd is the standard Apache utility specifically designed to create and update flat-file databases (.htpasswd files) containing usernames and encrypted passwords for basic authentication. When Apache is configured to use AuthUserFile to point to such a file, htpasswd is the program used to manage the user credentials within that file.
Incorrect:

A. htaccess

.htaccess (Hypertext Access) is a per-directory configuration file that Apache reads. It‘s used to enable authentication (e.g., specifying AuthType, AuthName, AuthUserFile), but it is not a program for adding users to the database. It‘s where you configure Apache to use the database created by htpasswd.
C. passdb

passdb is a generic term for a password database. While htpasswd creates a type of password database, passdb itself is not a specific program or command for adding users in the context of Apache authentication.
D. apacheadd

There is no standard Apache utility named apacheadd for adding users to an authentication database.

Correct:

B. recursion no;
In BIND‘s named.conf file, placing recursion no; within the options { … }; block (global options) disables recursive queries for all clients by default. This means the DNS server will only answer authoritative queries for zones it hosts and will not perform recursive lookups for clients to resolve names outside of its authoritative zones. This is a common security hardening step for authoritative-only DNS servers.
Incorrect:

A. recursion {none; };

While recursion is the correct directive, the syntax {none;} is incorrect. The recursion directive takes yes or no as a boolean value, not an ACL-like list or none.
C. allow-recursive-query {none; };

The correct directive for controlling recursion is recursion. allow-recursive-query is not a standard BIND directive. While allow-recursion exists, it‘s used to define who is allowed to make recursive queries if recursion is enabled, not to disable it globally by default.
D. allow-recursive-query off;

Similar to option C, allow-recursive-query is not the correct directive. Even if it were, off is not the standard boolean value for BIND directives; no is typically used. The directive to disable recursion globally is recursion no;.

Correct:

B. SSLCertificateKeyFile
This is the correct Apache HTTP Server directive used within a VirtualHost or server configuration to specify the path to the RSA (or other algorithm) private key file associated with the SSL/TLS certificate. It tells Apache where to find the cryptographic key needed to decrypt incoming SSL/TLS traffic and to prove the server‘s identity.
Incorrect:

A. SSLKeyFile

While intuitively sounding correct, SSLKeyFile is not the standard or correct directive name in Apache for specifying the private key. Apache‘s SSL/TLS module (mod_ssl) uses SSLCertificateKeyFile.
C. SSLPrivateKeyFile

Similar to SSLKeyFile, this is a plausible but incorrect directive name. The standard Apache directive is SSLCertificateKeyFile.
D. SSLRSAKeyFile

While the question specifically mentions an RSA private key, Apache‘s directive SSLCertificateKeyFile is general and handles various key types (RSA, ECC, etc.) without needing to specify the algorithm in the directive name itself. SSLRSAKeyFile is not a valid directive.

Correct:

C. In a VirtualHost directive
SSL/TLS (HTTPS) configuration, including directives like SSLEngine On, SSLCertificateFile, and SSLCertificateKeyFile, is almost exclusively configured within a block in Apache. This allows you to serve secure content for specific domains (virtual hosts) and separate the SSL configuration for different websites hosted on the same server, often distinguished by IP address or hostname. While you can enable SSL globally in the main server configuration, it‘s far more common and flexible to do it per VirtualHost.
Incorrect:

A. In a Directory Policy that is defined as /

A “Directory Policy“ typically refers to directives within blocks or .htaccess files. While you can put some access control or authentication directives in these contexts, SSLEngine and other core SSL directives are not permitted within or .htaccess contexts. They must be at the server or virtual host level. Enabling SSL for the root directory would effectively apply it globally, but the proper directive location is a VirtualHost or global server config.
B. In an SSLHost policy

There is no standard Apache directive or concept called “SSLHost policy.“ SSL configuration is integrated directly into VirtualHost or global server directives.
D. In a Local policy

“Local policy“ is a vague term and not a specific Apache configuration context. Apache‘s configuration structure relies on contexts like server config, VirtualHost, Directory, Files, and .htaccess.

Correct:

B. The network is working, but the name is not yet running, so Apache is unable to perform a DNS check on the virtual hosts.

If Apache starts before the named (BIND) DNS server daemon, Apache will attempt to resolve the hostnames specified in its VirtualHost directives. If the local DNS server isn‘t running yet, these lookups will fail, leading to errors. This is a common race condition during system startup where services have dependencies on each other.
D. The network is not yet configured, so Apache is unable to perform a DNS check on the virtual hosts.

For Apache to perform DNS lookups for VirtualHost entries (especially NameVirtualHost based on hostnames), the system‘s networking must be fully initialized. If network interfaces are down, IP addresses aren‘t assigned, or routing isn‘t set up, the system won‘t be able to reach any DNS server (even a local one), leading to resolution failures for virtual hosts.
Incorrect:

A. The VirtualHost directives for hosts are incorrect in the httpd.conf file.

While incorrect VirtualHost directives would cause errors, the question specifies “During system startup, you see messages complaining that Apache is unable to resolve any VirtualHost entries.“ This wording implies a resolution problem, not a syntax problem. If the directives were syntactically incorrect, Apache would typically report syntax errors during its configuration parsing phase (often before it even tries to resolve names), or refuse to start at all.
C. The Apache process died before the virtual hosts were configured correctly.

If the Apache process died, you wouldn‘t be seeing messages about it “complaining.“ Instead, you‘d see messages about Apache failing to start or crashing. The error message “unable to resolve any VirtualHost entries“ specifically points to a DNS resolution issue, not a process crash related to configuration.

Correct:

A. DocumentRoot
This Apache directive specifies the directory from which Apache will serve files for a given web site or virtual host. For example, if DocumentRoot /var/www/html is set, and a user requests http://example.com/index.html, Apache will look for /var/www/html/index.html. This is the core directive for defining the web-accessible content location.
Incorrect:

B. ServerRoot

ServerRoot specifies the top-level directory where the Apache HTTP Server‘s configuration files, error logs, and module directories are located. It defines the base directory for the Apache installation itself, not the directory from which web documents are served to clients.
C. Location

The directive (or ) is a container directive used to apply configuration directives to specific URLs (URI paths) regardless of where they are stored in the filesystem. It‘s used for access control, authentication, etc., for a URL path, but it does not define the main document root for the site.
D. DirectoryIndex

DirectoryIndex specifies the file that Apache will serve when a user requests a directory instead of a specific file (e.g., index.html, index.php). It defines the default file name to look for within a directory, but it does not define the root directory for the entire site.
E. UserDir

UserDir (User Directory) allows users to serve web content from their home directories (e.g., http://example.com/~username/). It specifies a subdirectory within a user‘s home directory (e.g., public_html) from which content can be served, but it is not used to configure the main document root for the primary website or virtual host.

Correct:

A. dnsmasq

dnsmasq is a lightweight DNS forwarder, DHCP server, and TFTP server. It‘s commonly used on small networks (like home routers) or for caching and local DNS resolution on individual hosts. It‘s a popular alternative to BIND, especially where a full-fledged, high-performance authoritative server isn‘t needed.
B. djbdns

djbdns (Dan J Bernstein‘s DNS) is a collection of DNS tools, including tinydns (an authoritative DNS server) and dnscache (a caching DNS server). It was developed with a strong focus on security and is a well-known alternative to BIND, although its development has been less active in recent years compared to other alternatives.
Incorrect:

C. dnstiny

This is a plausible-sounding name, possibly a slight variation or misconception related to tinydns (part of djbdns), but it is not a standalone, widely recognized alternative DNS software package in its own right.
D. superdns

This is not a recognized or standard alternative DNS software package in the Linux ecosystem.
E. easydns

easydns is primarily a commercial DNS hosting provider service, not a standalone open-source DNS server software package that you would install and run on your own Linux server.

Correct:

A. req

The openssl req subcommand is used for Certificate Signing Request (CSR) management. Specifically, openssl req -new -key … -out … is used to create a new CSR. It prompts for information like organization name, common name, etc., which are then included in the CSR.
D. genrsa

The openssl genrsa subcommand is used to generate RSA private keys. Before you can create a CSR, you need a private key. openssl genrsa -out private.key 2048 is a common way to generate a 2048-bit RSA private key and save it to a file.
Incorrect:

B. csr

While csr is an abbreviation for Certificate Signing Request, it is not a direct subcommand of openssl for generation. The correct subcommand for CSR operations is req.
C. gencsr

This is not a standard openssl subcommand. The functionality for generating CSRs is provided by the req subcommand.
E. genkey

This is not a standard openssl subcommand. While it intuitively sounds like it would generate a key, the specific subcommand for generating RSA keys is genrsa. For other types of keys (like ECC), different gen subcommands exist (e.g., genpkey).

Correct:

A. Squid
Squid is a widely used open-source web proxy cache. Its primary function is to cache frequently accessed web content (like HTML pages, images, and other files) on a server. When a client requests a resource that Squid has in its cache, Squid can deliver it directly, significantly reducing load on the origin web server, decreasing bandwidth usage, and improving response times for subsequent client requests for that same content.
Incorrect:

B. CGI

CGI (Common Gateway Interface) is an older standard for external programs to interface with web servers. It allows web servers to execute scripts (written in languages like Perl, Python, C, etc.) to generate dynamic web content. CGI is about generating content, not caching it.
C. PHP

PHP is a popular server-side scripting language primarily used for web development to create dynamic web pages and applications. Like CGI, PHP is used to produce web content (often by interacting with databases), not to cache web access by clients.
D. lynx

Lynx is a text-based web browser. It is a client-side application used to view web pages, not a server-side tool that caches web access for multiple clients or improves network performance for a group of users.

Correct:

A. ServerRoot
The ServerRoot directive specifies the top-level directory where the Apache HTTP Server‘s core configuration files (like httpd.conf), module directories, logs, and other server-related files are located. Other directives within the configuration often use paths relative to ServerRoot. For example, ErrorLog logs/error_log would typically resolve to $ServerRoot/logs/error_log.
Incorrect:

B. ServerType

The ServerType directive was used in older versions of Apache (Apache 1.x) to specify whether the server ran in standalone or inetd mode. It has been deprecated since Apache 2.0 and is not used to define the path to configuration files.
C. ConfigDir

ConfigDir is not a standard Apache directive. There is no such directive to specify the configuration directory.
D. DocumentRoot

DocumentRoot specifies the directory from which Apache serves web content (e.g., HTML, images) to clients. It defines the root of the website, not the location of the server‘s own configuration files.

Correct:

D. 600
File permissions of 600 (rw——-) mean that only the owner of the file has read and write access, and no one else (group or others) has any access. For private key files on an Apache server (or any server), this is the most secure permission setting. The private key should be readable only by the user account that Apache runs as, and ideally only writable by root during initial setup. Denying access to everyone else is critical to prevent unauthorized access to the key, which would compromise the security of your HTTPS connections.
Incorrect:

A. 660

Permissions of 660 (rw-rw—-) mean the owner has read/write, and the group also has read/write. This is too permissive for a private key. If another user is part of the same group as the Apache user, they could read the private key, which is a significant security risk.
B. 644

Permissions of 644 (rw-r–r–) mean the owner has read/write, the group has read-only, and others have read-only. This is highly insecure for a private key. It would allow any user on the system to read the private key, completely defeating the purpose of strong encryption.
C. 640

Permissions of 640 (rw-r—–) mean the owner has read/write, the group has read-only, and others have no access. While better than 644, it‘s still too permissive. If another user is part of the same group as the Apache user (e.g., www-data or apache), they could read the private key. Only the specific user account running Apache should have read access.

Correct:

A. Redirection is handled on the client side.

Redirect (and RedirectMatch) directives tell the client‘s web browser that the requested resource has moved. The Apache server sends an HTTP redirection response (e.g., a 301 Moved Permanently or 302 Found status code) along with the new URL in the Location header. The client‘s browser then initiates a new request to the new URL. This is a client-side action.
E. Alias is handled on the server side.

The Alias directive maps a URL path to a filesystem path. When a client requests a URL that matches an Alias, the Apache server directly serves the content from the specified filesystem location. The client is unaware that the content is coming from a different path on the server; the entire process happens internally within the server. This is a server-side action.
Incorrect:

B. Alias is not a valid configuration policy.

Alias is a perfectly valid and commonly used Apache configuration directive. It allows you to serve content from directories outside of the DocumentRoot while maintaining a clean URL structure.
C. Alias can only reference files in DocumentRoot.

This statement is false and is the opposite of the Alias directive‘s primary purpose. Alias is specifically used to map a URL to a directory that is outside of the DocumentRoot. If the content were already within the DocumentRoot, you wouldn‘t typically need an Alias for it.
D. Redirection works with regular expressions.

While Redirect works with simple prefix matching, the more powerful RedirectMatch directive does work with regular expressions. However, the statement only says “Redirection works with regular expressions,“ which is only partially true (specifically for RedirectMatch). Redirect itself does not use regex. Given that the question implies a general statement about “Redirection,“ and one form does use regex, it‘s not strictly incorrect that a form of redirection uses regex, but compared to the other options, it‘s not the most precise and doesn‘t fully describe the core Redirect directive. The question asks for true statements, and option A and E are unequivocally true about the fundamental mechanisms.

Correct:

C. SSLEngine
The SSLEngine directive is the core Apache mod_ssl module directive used to explicitly turn SSL/TLS processing on or off for a particular virtual host or server context. When set to SSLEngine On, Apache will listen for and process HTTPS connections on that specific configured port and virtual host. This is the fundamental switch to enable HTTPS.
Incorrect:

A. SSLEnable

While SSLEnable sounds like it would enable SSL, it is not a standard Apache directive. The correct directive is SSLEngine.
B. HTTPSEnable

HTTPSEnable is not a standard Apache directive. Apache‘s secure communication module uses “SSL“ in its directive names, even though the underlying protocol is now primarily TLS.
D. HTTPSEngine

Similar to HTTPSEnable, HTTPSEngine is not a standard Apache directive. The mod_ssl module uses SSLEngine for this purpose.

Correct:

C. Apache needs to start as root to connect to port 80. On Unix-like systems (including Linux), only the root user can bind to privileged ports (ports below 1024), such as port 80 (HTTP) and port 443 (HTTPS). When Apache is configured to run inside a chroot prison, it still needs to initially bind to these ports before it drops privileges to a non-root user. If the startup script or process that launches Apache attempts to start it directly as a non-root user, it will fail to bind to port 80, resulting in the inability to start. The typical procedure is for Apache to start as root, bind to the privileged port, perform the chroot(), and then setuid()/setgid() to the less privileged user for ongoing operations.
Incorrect:

A. A LoadModule line for mod_chroot needs to be added to httpd.conf.
There isn‘t a standard Apache module specifically named mod_chroot that is loaded via LoadModule to enable chroot. Chrooting Apache is typically achieved by launching the httpd binary with the -t option (e.g., httpd -t /path/to/chroot) or by configuring the service manager (like systemd) with RootDirectory=.

B. The mod_chroot configuration needs the absolute path to the chroot environment.
As mentioned in A, mod_chroot isn‘t a standard module. While the path to the chroot environment is indeed absolute and crucial, the problem described (Apache not starting) is more fundamental regarding port binding, not just a path configuration.

D. Apache is unable to read the main index.html file because it has not been moved to the chroot environment.
While it‘s true that all necessary files (including index.html, configuration files, modules, libraries, log directories, etc.) must be present inside the chroot environment for Apache to function correctly after it has chrooted, the problem here is that httpd “no longer starts.“ This usually implies a failure during the initial setup phase (like binding to a port), before it even gets to the point of serving content from index.html. If index.html were missing, Apache might start but then return 404 errors for requests.

E. Apache requires a VirtualHost directive when running from a chroot environment.
Apache does not inherently require a VirtualHost directive simply because it‘s running in a chroot environment. You can run a single, default server configuration within a chroot without explicit VirtualHost directives. VirtualHost directives are for hosting multiple domains or serving different content based on hostname/IP, not a prerequisite for chrooting.

Correct:

C. .htaccess
.htaccess (Hypertext Access) is the correct and standard file name used by Apache to allow decentralized, directory-level configuration. When enabled, Apache looks for .htaccess files in directories it serves, and directives within these files apply to that directory and its subdirectories. This allows users or developers to override or add specific Apache configurations without needing to modify the main server configuration files.
Incorrect:

A. .apache

This is not a standard or recognized Apache configuration file name.
B. .httpd

While httpd is the name of the Apache daemon, .httpd is not a standard configuration file name for per-directory settings. The main Apache configuration file is typically httpd.conf (or apache2.conf on some distributions), not a hidden file in a directory tree.
D. .apache-config

This is not a standard or recognized Apache configuration file name.

Correct:

B. SSLVerifyClient require
This is the correct Apache mod_ssl directive to enforce client certificate authentication. When SSLVerifyClient require is set within an SSL enabled context (like a VirtualHost), Apache will only allow clients to establish an SSL/TLS connection if they present a valid client certificate that can be verified against the Certificate Authorities (CAs) configured on the server (via SSLCACertificateFile or SSLCACertificatePath). If the client does not present a certificate or if it cannot be verified, the connection will be rejected.
Incorrect:

A. AuthType ssl

AuthType is used in conjunction with authentication modules (like mod_auth_basic or mod_authz_dbm) to specify the authentication scheme (e.g., Basic, Digest). While SSL client certificates are a form of authentication, AuthType ssl is not a valid or standard directive for enforcing client certificate validation. The SSLVerifyClient directive handles this.
C. SSLRequire

SSLRequire is an Apache directive that allows for more granular control over access based on client certificate properties (e.g., specific OUs, common names, or serial numbers) after the certificate has been presented and verified. It‘s used for authorization, but it doesn‘t require the client to present a certificate in the first place. That function belongs to SSLVerifyClient.
D. SSLCA conf / ca.crl

SSLCA is not a standard Apache directive. The directive used to specify the Certificate Authority (CA) certificate file(s) that Apache uses to verify client certificates is SSLCACertificateFile or SSLCACertificatePath. ca.crl also suggests a Certificate Revocation List (CRL), which would be configured with SSLCARevocationFile or SSLCARevocationPath, not for requiring certificates.
E. IfModule libexec / ssl.c

(or more commonly mod_ssl.c) is a container directive that checks if a specific module (in this case, mod_ssl) is loaded. It ensures that the directives inside it are only processed if the module is active. It does not, by itself, enable or require client certificates; it just provides a conditional block for other SSL-related directives.

Correct:

D. auth_param
auth_param is the Squid configuration directive used to define the parameters for an authentication scheme. This includes specifying the authentication method (e.g., basic, digest, ntlm, negotiate) and the external helper program that will perform the actual authentication (e.g., basic_ncsa_auth). It‘s a versatile directive that allows for various authentication backends and settings.
Incorrect:

A. auth_method

This is not a standard Squid configuration directive. The method is specified as part of the auth_param directive (e.g., basic in auth_param basic program …).
B. auth_program

While you specify an authentication program (helper) within Squid‘s configuration, auth_program itself is not the directive that defines the authentication method. The program is a parameter of auth_param.
C. proxy_auth

proxy_auth is a keyword used in ACLs (e.g., acl authenticated proxy_auth REQUIRED) to check if a user has successfully authenticated. It is not a directive for defining the authentication method itself.
E. auth_mechanism

This is not a standard Squid configuration directive. Similar to auth_method, it‘s a plausible-sounding term but incorrect for Squid‘s syntax.

Correct:

B. proxy_auth
proxy_auth is the specific ACL type in Squid that matches based on successful user authentication. When you define an ACL like acl authenticated_users proxy_auth REQUIRED, it means that this ACL will match only if the client has successfully authenticated to the proxy using credentials provided (e.g., via a pop-up prompt).
Incorrect:

A. auth

While “auth“ is related to authentication, auth by itself is not a valid ACL type in Squid‘s configuration. ACL types are specific keywords like src, dst, port, time, url_regex, proxy_auth, etc.
C. proxy_passwd

proxy_passwd is not an ACL type in Squid. Password files (e.g., created with htpasswd) are used by the authentication helper programs that Squid uses, but this is not an ACL type itself.
D. proxyAuth

Squid‘s configuration directives and ACL types are typically lowercase with underscores (e.g., proxy_auth). proxyAuth (camelCase) is not the correct syntax for an ACL type.
E. auth_required

auth_required is not an ACL type. The keyword REQUIRED is often used as a parameter to the proxy_auth ACL type (e.g., acl myauth_acl proxy_auth REQUIRED) to indicate that authentication is necessary for this ACL to match. It‘s not an ACL type on its own.

Correct:

E. acl local src 192.168.1.0/24 http_access allow local
This is the correct and standard way to configure an Access Control List (ACL) and then apply it to control HTTP access in Squid.
acl local src 192.168.1.0/24: This line defines an ACL named local. The src type specifies that this ACL matches based on the source IP address of the client. 192.168.1.0/24 is the network range that this ACL will match.
http_access allow local: This line then uses the defined ACL. http_access is the directive that controls access to the proxy. allow is the action (permit access). local refers to the ACL named local defined in the previous line. This entire statement means: “Allow HTTP access if the client‘s source IP address matches the local ACL (i.e., comes from the 192.168.1.0/24 network).“
Incorrect:

A. acl local src 192.168.1.0/24 httpd local allow

httpd is the name of the Apache daemon, not a Squid directive. The correct directive for controlling HTTP access in Squid is http_access. The order of local allow is also incorrect; it should be allow local.
B. acl local src 192.168.1.0/24 http access allow local

The directive http access is missing the underscore. The correct directive is http_access.
C. acl local src 192.168.1.0/24 http_allow local

http_allow is not a standard Squid directive. The correct directive is http_access.
D. acl local src 192.168.1.0/24 http_access_allow = local

http_access_allow is not a standard Squid directive, and the = sign is incorrect syntax for applying an ACL in an http_access rule.

Correct:

A. As the first line of the zone file.
The $TTL directive in a BIND zone file sets the default Time-To-Live for all resource records that follow it, unless a specific TTL is defined for an individual record. According to standard DNS zone file format (RFC 1035 and subsequent updates), $TTL is a special directive that should be placed at the very beginning of the zone file, before any resource records (including the SOA record) are defined. This ensures that the default TTL is established before it‘s needed for the SOA record itself and any subsequent records.
Incorrect:

B. In the SOA record of the zone file.

The SOA (Start of Authority) record itself has a TTL, but the $TTL directive is not placed within the SOA record‘s fields. The SOA record‘s TTL is typically one of its parameters, and if no explicit TTL is given for the SOA record, it will inherit the value from the $TTL directive set at the top of the file.
C. In any zone file containing hints for the root servers.

Hint files (often named.ca or db.cache) contain information about the root servers. While they also use TTLs, the $TTL directive‘s placement rule applies to authoritative zone files (like db.example.com), not specifically to root hints files, although the concept of default TTL is similar. The question specifically refers to “a BIND zone file,“ which usually implies an authoritative zone.
D. It is needed just before any A records are defined.

While the $TTL applies to A records (and all other records), placing it just before A records is incorrect. It sets the default for the entire file and must come before any resource records, including the SOA record, which is always the first actual record in a zone file.

Correct:

C. Its use may occasionally cause data loss.

kill -9 sends the SIGKILL signal, which cannot be caught or ignored by a process. This forces the immediate termination of the process without giving it any chance to clean up, close open files, save unsaved data, or perform graceful shutdown procedures. If a process is in the middle of writing to a file or a database, for example, sending SIGKILL can result in corrupted files or data loss because the write operation is abruptly halted.
D. Its use must be avoided and other alternatives must be tried before it.

This is a fundamental best practice for process management. SIGKILL (kill -9) is a last resort. Before using kill -9, administrators should always attempt more graceful termination signals, such as SIGTERM (kill without a specified signal, or kill -15). SIGTERM allows a process to catch the signal, perform cleanup operations (like saving data, closing files, flushing buffers), and then exit gracefully. Only if a process fails to respond to SIGTERM or is genuinely unresponsive should kill -9 be considered.
Incorrect:

A. It is possible that zombie processes can be created as a result of their use.

Zombie processes (defunct processes) occur when a child process terminates, but its parent process has not yet reaped its exit status. Sending kill -9 to a process typically terminates that specific process. If the process being killed is a parent process, its children might become orphaned (adopted by init), but the kill -9 itself doesn‘t directly create zombie processes from the targeted process. Zombies are a result of parent-child process management, not typically a direct consequence of a SIGKILL on the child.
B. Its frequent use can increase RAM usage.

kill -9 is about terminating processes and freeing up resources. Its frequent use would generally lead to decreased RAM usage as processes are forcefully removed from memory. It does not cause an increase in RAM usage; in fact, the opposite is true.
E. It can always be used without restrictions.

This is dangerously incorrect. As explained in options C and D, kill -9 is a forceful and ungraceful termination method that carries significant risks, including data loss and system instability if critical processes are killed. It should always be used with caution and as a last resort, not “without restrictions.“

Correct:

C. AuthType
The AuthType directive in Apache specifies the type of authentication to be used for a given realm (a protected area of the website). Common values are Basic (which uses simple username/password, often stored in .htpasswd files) and Digest. This directive is fundamental for setting up HTTP authentication.
Incorrect:

A. AllowedAuthUser

This is not a standard Apache directive. Access control based on authenticated users is typically handled by directives like Require user, Require valid-user, or Require group in conjunction with authentication.
B. AllowAuth

This is not a standard Apache directive. The correct directive for specifying the authentication scheme is AuthType.
D. AuthUser

AuthUser is not a standard Apache directive. The directive used to specify the file containing usernames and passwords is AuthUserFile (e.g., AuthUserFile /etc/apache2/.htpasswd). AuthUser by itself has no meaning in this context.

Correct:

B. It is the name of the zone, as defined in the zone declaration in named.conf.
In a BIND zone file, the @ symbol is a special shorthand that represents the origin of the zone. The origin is the domain name for which the zone file is authoritative, as specified in the zone statement in named.conf. For example, if named.conf has zone “example.com“ { type master; file “db.example.com“; };, then inside db.example.com, @ refers to example.com. This makes zone files more concise.
Incorrect:

A. It is an alias for the email address of the master zone.

While an email address appears in the SOA record, the @ symbol in the SOA record‘s RNAME field (the responsible person‘s email) is typically escaped with a backslash (e.g., admin\.example.com.) to distinguish it from the zone origin shorthand. The @ character (unescaped) as a name in the zone file always means the origin.
C. It is used to create an alias between two CNAME entries.

CNAME records are used to create aliases between one domain name and another. The @ symbol is used to represent the zone origin (the domain itself), not to link two CNAME entries together.
D. It is the fully qualified host name of the DNS server.

The fully qualified hostname of the DNS server is usually specified in NS (Name Server) records or A/AAAA records for the name server itself. The @ symbol refers to the zone‘s origin, which is the domain being served, not necessarily the hostname of the server serving it.

Correct:

B. allow-transfer {192.168.1.0/24; };
This is the correct and standard BIND configuration directive to control which IP addresses or networks are allowed to perform zone transfers (AXFR or IXFR) from the configured zone or server. The allow-transfer statement takes an Access Control List (ACL) as its argument, which can include IP addresses, network prefixes (like 192.168.1.0/24), or named ACLs. When placed within a zone block, it applies only to that specific zone. When placed in the options block, it applies globally to all zones unless overridden by a zone-specific allow-transfer directive.
Incorrect:

A. allow-axfr {192.168.1.0/24; };

While AXFR (Asynchronous Zone Transfer) is a type of zone transfer, allow-axfr is not the correct or standard BIND configuration directive. The general directive for all types of zone transfers (AXFR and IXFR) is allow-transfer.
C. allow-xfer {192.168.1.0/24; };

Similar to option A, allow-xfer is not the correct or standard BIND configuration directive. The correct directive uses the full word “transfer“.
D. allow-transfer {192.168.1.0-192.168.1.0.255; };

While the directive allow-transfer is correct, the syntax for specifying the network range is incorrect. BIND uses CIDR notation (e.g., 192.168.1.0/24) or individual IP addresses, not a dash-separated range like this.

Correct:

D. Cache poisoning
DNSSEC (Domain Name System Security Extensions) provides cryptographic authentication of DNS data. Its primary purpose is to protect against cache poisoning (also known as DNS spoofing). Cache poisoning occurs when an attacker injects forged DNS data into a recursive DNS resolver‘s cache. When legitimate users query that resolver, they receive the malicious (spoofed) IP address instead of the correct one, redirecting them to attacker-controlled sites. DNSSEC digitally signs DNS records, allowing resolvers to cryptographically verify the authenticity and integrity of responses, thereby detecting and rejecting forged data.
Incorrect:

A. Social engineering

Social engineering relies on manipulating people to gain access to information or systems. DNSSEC is a technical solution for DNS data integrity and authenticity; it does not protect against human-based attacks like phishing or other forms of social engineering.
B. Transfers from unauthorized areas

Controlling zone transfers (preventing unauthorized secondary servers from obtaining a copy of your DNS zone data) is typically managed by the allow-transfer directive in BIND‘s named.conf configuration file, or by using TSIG (Transaction Signatures) for authentication during zone transfers. While security-related, this is not the direct purpose or primary mechanism of DNSSEC. DNSSEC focuses on the integrity of the data served rather than the transfer control itself.
C. Intruders on the server

DNSSEC does not directly protect the DNS server itself from being compromised by intruders (e.g., via exploiting vulnerabilities in the operating system or BIND software, or through weak credentials). While a compromised server could serve bad DNSSEC-signed data, DNSSEC‘s role is to verify the data‘s authenticity after it leaves the server, not to prevent the server from being intruded upon. Other security measures like firewalls, system hardening, timely patching, and chroot jails are designed to mitigate server intrusion.

Correct:

D. blackhole { …; };
This is the correct BIND configuration option. The blackhole statement in the options block is used to specify a list of IP addresses or network prefixes from which queries should be silently dropped. The BIND server will not respond to any queries originating from IP addresses listed in the blackhole ACL (Access Control List). This is often used to ignore queries from known malicious or troublesome networks, effectively making them “disappear“ into a black hole from the server‘s perspective.
Incorrect:

A. no-answer { …; };

This is not a standard BIND configuration guideline or keyword for the purpose described.
B. deny-answer { …; };

This is not a standard BIND configuration guideline or keyword. While it sounds plausible, blackhole is the actual directive used to deny all responses.
C. deny-query { …; };

While deny-query sounds functionally similar, it is not the correct or standard BIND directive for this purpose. The standard way to deny queries from specific sources is blackhole. There is also an allow-query directive that explicitly lists allowed query sources, and by omission, others are denied, but deny-query as a standalone concept for blocking is not the primary mechanism here.
E. deny-access { …; };

This is not a standard BIND configuration guideline or keyword. Access control for BIND is managed through various allow-* directives (e.g., allow-query, allow-recursion, allow-transfer, allow-update) and the blackhole directive. deny-access is not a valid option.

Correct:

A. The directory must not have the read permission set.
To prevent users from listing file names in a directory, the directory must not have the read permission (r) set for the user or group that the anonymous FTP user operates as (typically other or a specific FTP user/group). Without read permission on the directory, the FTP server cannot read the directory‘s contents and thus cannot list the files to the anonymous user.
Incorrect:

B. The directory must not contain other directories.

While having many nested directories might make management harder, it doesn‘t inherently prevent listing of file names within the current directory. This is not a direct security measure for preventing directory listings.
C. The directory must not have the execute permission set.

Execute permission (x) on a directory allows one to cd into it or access files within it if their names are known. Removing execute permission would prevent users from entering the directory, but it doesn‘t directly address preventing the listing of files if the user can still ls from the parent directory (which is often the case with FTP). For an upload directory where you want files to be uploaded but not listed, execute permission is often required along with write, to allow the server process to navigate into the directory to place files, but read permission is what enables listing.
D. The directory must not have the write permission set.

If the directory does not have write permission (w), then anonymous FTP users would not be able to upload files to it at all. The question specifically mentions “listing uploaded file names,“ implying that uploads are allowed. Removing write permission would make it an upload-proof directory, which goes against the premise.
E. The directory must not have the read or execute permission set.

While removing read permission (as per A) is correct for preventing listing, also removing execute permission (x) would prevent the anonymous FTP user from even accessing or navigating into the directory to upload files. If the goal is to allow uploads but prevent listing, execute permission is often needed for navigation, while read permission is removed for listing prevention.

Correct:

B. The use of the pam_nologin module along with the /etc/nologin configuration file.
PAM (Pluggable Authentication Modules) is a highly configurable framework for user authentication. The pam_nologin module is specifically designed for this purpose. When the pam_nologin.so module is configured in the PAM stack (typically in files like /etc/pam.d/login or /etc/pam.d/sshd), it checks for the existence of the /etc/nologin file.
If /etc/nologin exists, all non-root users will be denied login. The content of /etc/nologin is displayed to the user as a message explaining why they cannot log in. The root user is typically exempt from this restriction, allowing administrators to still access the system for maintenance.
Incorrect:

A. The use of the pam_deny module along with the /etc/deny configuration file.

The pam_deny module does deny access, but it‘s used to unconditionally deny authentication (e.g., as the last resort in a PAM stack if no other module succeeded). It does not, by itself, check for a specific file like /etc/deny to enable a system-wide non-root login block. There is no standard /etc/deny file for this purpose.
C. The use of the pam_pwdb module along with the /etc/pwdv.conf configuration file.

The pam_pwdb module is used for authentication against traditional Unix password databases (like /etc/passwd and /etc/shadow). It‘s fundamental for local user authentication but has no direct mechanism to disable logins for all users except root based on a configuration file like /etc/pwdv.conf (which is not a standard file for this purpose).
D. The use of the pam_block module along with the /etc/login configuration file.

There is no standard PAM module named pam_block. While /etc/login might refer to a PAM configuration file for the login service, the specific module and configuration file mentioned are incorrect for this task.

Correct:

A. qshape
qshape is a Postfix utility specifically designed to display Postfix queue contents in a “shape“ by destination. It provides a quick overview of how many messages are in the queue for each destination, along with the age of the oldest message. This makes it extremely useful for identifying remote sites (destinations) that are either slow to accept mail or are causing backlogs due to excessive traffic, thus creating a “hump“ in the queue.
Incorrect:

B. postmap

postmap is a Postfix utility used to create or query Postfix lookup tables (like hash maps, btree maps, etc.). These tables are used for various configurations (e.g., aliases, virtual domains, access control lists). It has nothing to do with displaying the contents of the mail queue or identifying traffic patterns.
C. mailtraf

mailtraf is not a standard Postfix command-line utility for queue analysis. While “mail traffic“ is relevant to the question, this specific command name is incorrect.
D. queuequery

queuequery is not a standard Postfix command-line utility. Postfix uses mailq or postqueue -p for basic queue listing and qshape for detailed queue analysis.
E. poststats

poststats is not a standard Postfix command-line utility for queue analysis. Postfix provides logging and reporting mechanisms, but poststats is not part of its standard set of tools for inspecting the live queue content.

Correct:

A. ftp

ftp is one of the universally recognized and standard usernames for anonymous FTP access. When anonymous_enable=YES is set in vsftpd.conf, vsftpd will treat a login with the username ftp as an anonymous login.
C. anonymous

anonymous is the other universally recognized and standard username for anonymous FTP access. Similar to ftp, vsftpd will recognize a login with the username anonymous as an anonymous login when the anonymous_enable option is enabled.
Incorrect:

B. guest

While guest might be used in some contexts or for specific guest accounts, it is not one of the default, universally recognized anonymous FTP usernames by vsftpd or the FTP protocol itself. vsftpd needs to be explicitly configured to handle a guest login in a special way if desired, but it‘s not treated as anonymous by default.
D. nobody

The nobody user typically represents a user with minimal privileges on a Linux system, often used for processes that don‘t need specific user identities. It is not an anonymous FTP login username. Attempting to log in as nobody would likely be treated as a regular (non-anonymous) user login and require a password for the nobody user.
E. In the described configuration, any username which neither belongs to an existing user nor has another special meaning is treated as anonymous user.

This statement is incorrect. If anonymous_enable=YES is set, vsftpd still strictly expects either ftp or anonymous as the username for anonymous logins. Other arbitrary usernames (that are not actual system users) would typically result in a login failure, not an anonymous login. vsftpd is designed to be secure by default and doesn‘t implicitly treat unknown usernames as anonymous.

Correct:

C. client-to-client
This is the standard OpenVPN server configuration directive that enables direct communication between connected VPN clients through the OpenVPN server. When this option is enabled, the OpenVPN server itself handles the routing and forwarding of packets between clients on the VPN network, without sending them out to the underlying operating system‘s network stack for routing. This is particularly useful in mesh topologies or when clients need to directly access each other, rather than just accessing resources on the server‘s local network.
Incorrect:

A. grant-client-traffic

This is not a standard OpenVPN configuration option. While its name implies some form of client traffic management, it doesn‘t correspond to a known OpenVPN directive for inter-client routing.
B. client-pass

This is not a standard OpenVPN configuration option. OpenVPN uses various allow or push directives for client permissions or configuration, but client-pass is not one of them for this specific purpose.
D. client-router

This is not a standard OpenVPN configuration option. While OpenVPN servers act as routers for VPN clients, this specific directive does not exist to enable client-to-client forwarding.
E. inter-client-traffic

This is not a standard OpenVPN configuration option. It describes the functionality, but the correct directive is client-to-client.

Correct:

B. A server-specific system account
Running BIND (or any network service) with a dedicated, unprivileged system account is a fundamental security best practice. This account should have minimal necessary permissions, typically only read access to its configuration files and zone files, and write access to its cache and log directories. If the BIND process is compromised, the attacker will inherit the limited permissions of this dedicated user, severely restricting their ability to damage or access other parts of the system. On most Linux distributions, BIND is configured by default to run as a user like named or bind.
Incorrect:

A. A common login user account

Using a common login user account (e.g., john, mary) for a service is highly insecure. If that account were compromised, it would give an attacker access to that user‘s personal files and potentially other system resources that the user has permissions for. It also complicates management as the account might have a shell and other login capabilities that are unnecessary for a service.
C. The root account

Running any non-essential service as the root account is extremely dangerous and a major security vulnerability. If BIND were compromised while running as root, an attacker would gain full root privileges on the system, allowing them to do anything, including deleting all data, installing backdoors, or launching further attacks. This violates the principle of least privilege.
D. No one‘s account

Every process on a Linux system must run under some user ID and group ID. There is no concept of a process running “no one‘s account.“ Even if it appears to run without a specific user, it‘s typically running under a system-level pseudo-user or the kernel‘s context, which can still have security implications if not properly managed.

Correct:

D. The LDIF file accepts any type of file encoding.
LDIF (LDAP Data Interchange Format) files do not accept any type of file encoding. According to RFC 2849, LDIF files are expected to be in UTF-8 encoding. While older systems might have used other encodings like ISO-8859-1 for specific character sets, the standard and recommended encoding for LDIF is UTF-8 to ensure proper handling of diverse character sets. If other encodings are used, they typically need to be explicitly declared within the LDIF file using the charset attribute, but this doesn‘t mean any encoding is implicitly accepted or will work reliably without specific handling.
Incorrect:

A. In the file, a blank line separates one entry from another one.

This statement is correct. A fundamental rule of LDIF is that a blank line (or a line containing only whitespace) is used to separate distinct LDAP entries within the file. This helps the parsing tools identify the boundaries between different entries (e.g., adding a user, then adding a group).
B. If an attribute contains binary data, some specific configurations must be made for this entry.

This statement is correct. If an attribute‘s value contains binary data (e.g., a JPEG photo, a certificate), it cannot be represented directly as plain text. LDIF handles this by Base64 encoding the binary data. The attribute definition would typically include ::< after the attribute name to indicate Base64 encoding, and the following lines would contain the Base64-encoded string. Tools processing the LDIF would then decode it.
C. It contains a dn line that indicates where the attributes listed in the following lines of the file must be added.

This statement is correct. Every LDAP entry in an LDIF file begins with a dn: line, which specifies the Distinguished Name (DN) of the entry. This DN uniquely identifies the entry within the LDAP directory tree and dictates its location. All subsequent attribute lines until a blank line or a new dn: line belong to that specific entry.

Correct:

B. PTR
PTR (Pointer) records are specifically used for reverse DNS lookups. They map an IP address to a hostname. For IPv4, these records are stored in zones under the in-addr.arpa domain (e.g., 1.2.3.4 would map to 4.3.2.1.in-addr.arpa). For IPv6, they are under ip6.arpa.
Incorrect:

A. CNAME

CNAME (Canonical Name) records are used to create aliases for hostnames. They map one hostname to another hostname (e.g., http://www.example.com to server1.example.com). They are not used for IP-to-hostname mapping.
C. REV

REV is not a standard DNS record type. While “reverse“ is related to the query, the actual record type is PTR.
D. IN

IN stands for “Internet“ and is a class type in DNS records, not a record type itself. It indicates that the record belongs to the Internet class of DNS data. For example, example.com IN A 192.0.2.1.
E. RIN

RIN is not a standard DNS record type.

Correct:

C. dig

dig (domain information groper) is a powerful and flexible command-line tool for querying DNS name servers. It provides detailed information about DNS lookups, including the queried server, response time, record types (A, MX, NS, SOA, etc.), TTLs, and flags. Its verbose output is invaluable for diagnosing complex DNS issues, including delegation problems, missing records, and DNSSEC validation.
D. nslookup

nslookup (name server lookup) is another command-line tool for querying DNS name servers. While dig is generally preferred by DNS professionals for its detail and consistency, nslookup also provides useful information for diagnosis, particularly its interactive mode which allows for multiple queries and changing servers within a session. It can resolve hostnames to IP addresses and vice-versa, query specific record types, and specify the DNS server to use.
Incorrect:

A. ping

ping is used to test network connectivity to a host by sending ICMP echo request packets and listening for echo replies. While you can ping a DNS server‘s IP address to check if it‘s reachable at the network layer, ping does not provide any information about the DNS service itself (e.g., if it‘s correctly resolving names, if its zones are configured properly, or if it‘s responding to DNS queries). It only checks basic network reachability.
B. nmap

nmap (Network Mapper) is a powerful network discovery and security auditing tool. It can be used to scan ports on a DNS server (e.g., UDP/TCP port 53) to see if the service is listening. However, nmap is a port scanner; it does not perform DNS lookups or provide detailed DNS-specific diagnostic information about the correctness or content of DNS zones. While it can confirm the service is running, it won‘t tell you if the DNS server is actually resolving names correctly.

Correct:

B. reload
The rndc reload subcommand, when used with a zone name (e.g., rndc reload example.com), instructs the BIND daemon (named) to reread the configuration for that specific zone and reload its zone file from disk. This is a crucial command for applying changes to a single zone file (like adding a new A record) without disrupting service for all other zones hosted on the server, which would happen with a full rndc reload (without a zone name) or a service restart.
Incorrect:

A. lookup

There is no rndc lookup subcommand. rndc is for controlling the daemon, not for performing DNS lookups directly. DNS lookups are performed with tools like dig, nslookup, or host.
C. zoneupdate

This is not a standard rndc subcommand. While it conceptually relates to updating zones, the specific command to reread a zone‘s file is reload. Dynamic updates (DDNS) are handled differently, not via rndc zoneupdate.
D. reread

While reread describes the action, it is not the actual rndc subcommand. The correct command is reload.
E. fileupdate

This is not a standard rndc subcommand. rndc subcommands are typically designed for broader daemon control rather than specific file operations in this manner.

Correct:

E. /var/log/messages
When users are unable to resolve local hostnames but can resolve external ones, and hosts are accessible by IP, this often points to an issue with the local DNS server‘s configuration for its authoritative zones, or a problem with how the client is querying the DNS server. In many Linux distributions, system-wide logs, including those from the BIND DNS server (unless explicitly configured to log elsewhere), are directed to /var/log/messages (or /var/log/syslog on Debian/Ubuntu-based systems). This file is the default catch-all for various system events, errors, and informational messages from daemons like named. It‘s the first place to check for errors reported by BIND about zone loading, syntax errors in zone files, or issues with local resolution.
Incorrect:

A. /var/named/log

While /var/named is where zone files are typically stored, /var/named/log is not a standard default log file location for BIND. BIND‘s logging is usually configured in named.conf, and it often defaults to syslog (which writes to /var/log/messages). If a custom log file is defined, it would be specified in named.conf and could be in this directory, but it‘s not the default.
B. /var/log/bind/errors

Some distributions might create a bind subdirectory under /var/log, but /var/log/bind/errors is not a universally default log file name for BIND errors. Logs are more commonly aggregated into messages or a dedicated named.log if explicitly configured.
C. /var/log/bind_errors

Similar to option B, this is not a standard default log file name for BIND.
D. /var/lib/named/dev/log

/var/lib/named is often used for BIND‘s run-time data, but /dev/log within that path is indicative of a Unix domain socket for syslog (or a chroot environment‘s log path), not a direct log file that an administrator would typically check for problems. The actual log messages would still be directed to the system‘s central log files (e.g., /var/log/messages) via syslog.

Correct:

E. Provide name resolution IP.
This option, while slightly awkwardly phrased (“name resolution IP“), correctly describes the core purpose of a PTR (Pointer) record. A PTR record performs reverse DNS resolution, meaning it maps an IP address back to its associated hostname. When you have an IP address and want to find out the hostname associated with it, you perform a reverse DNS lookup, and the DNS system uses PTR records to provide that information.

Incorrect:

A. Provide the name for the IP resolution.

This is essentially a rephrasing of the correct answer, but “name for the IP resolution“ is less clear than “Provide name resolution IP“ in the context of what a PTR record does (it provides the name from the IP). However, compared to other clearly incorrect options, it‘s closer to the truth than the rest. The best description is that it enables IP-to-name mapping.
B. To direct email to a specific host.

This is the purpose of an MX (Mail Exchanger) record. MX records specify which mail servers are responsible for accepting email for a domain. PTR records are not involved in directing email.
C. To direct clients to another name server.

This is the purpose of an NS (Name Server) record. NS records delegate authority for a domain or subdomain to specific name servers. PTR records have no role in delegating DNS authority.
D. To provide additional host information.

While other record types like TXT (Text) or SRV (Service) records can provide additional information, PTR records are solely focused on the IP-to-hostname mapping for reverse lookups. They don‘t provide general “additional host information.“

Correct:

B. authrequired pam_unix.sotry_first_pass nullok
This option, while appearing slightly unconventional with sotry_first_pass, is the most syntactically valid among the choices, representing a typical PAM configuration line. A PAM configuration line generally follows the format: module-type control-flag module-path arguments.
auth: The module type (authentication).
required: A control flag, meaning this module must succeed for authentication to continue, but its failure doesn‘t immediately stop the stack.
pam_unix.so: The path to the PAM module.
try_first_pass: An argument to the pam_unix module, instructing it to try the password obtained from a previous module.
nullok: Another argument, allowing a null password if the user‘s password field is empty.
The crucial aspect is the space separation between control-flag, module, and arguments. The absence of parentheses around arguments is correct for many PAM module arguments. The typo “sotry_first_pass“ might be intended to test recognition of the standard pam_unix.so module combined with its arguments. If sotry_first_pass is assumed to be a typo for try_first_pass, this line adheres to the general PAM syntax.
Incorrect:

A. authrequired:pam_unix.so(try_first_pass nullok)

The colon (:) after required is incorrect. PAM syntax requires a space between the control flag and the module path. Also, while some PAM modules might use parentheses for arguments, pam_unix.so typically takes arguments space-separated directly after the module name, not enclosed in parentheses like a function call.
C. authtry_first_pass nullok, require pam_unix.so

The order of elements is incorrect. The module type (auth) should be followed by the control flag (required, sufficient, etc.), then the module path, then its arguments. This option places arguments before the control flag and module, and uses a comma, which is not standard PAM syntax for separating arguments in this context.
D. authpam_unix.so(required try_first_pass nullok)

This line incorrectly places the control flag (required) inside parentheses with the module‘s arguments. The control flag must come directly after the module type. Also, similar to A, arguments for pam_unix.so are typically space-separated, not enclosed in parentheses.

Correct:

D. MX
MX (Mail Exchanger) records are specifically designed to identify the mail server(s) responsible for handling email for a particular domain. When an email is sent to [email protected], the sending mail server performs a DNS query for the MX record(s) for example.com to determine which host(s) to connect to for delivery.
Incorrect:

A. MAIL

MAIL is not a standard DNS record type. While it‘s related to email, it does not exist as a resource record type in DNS.
B. INBOX

INBOX is a common name for a user‘s primary mailbox on a mail server (e.g., in IMAP or POP3). It is not a DNS record type and has no role in identifying a mail server for a domain.
C. CNAME

CNAME (Canonical Name) records are used to create aliases from one domain name to another domain name. While a hostname pointed to by an MX record might itself be a CNAME to another host, the CNAME record itself does not identify the email server for the domain. The MX record is the one that points to the hostname designated as the mail exchanger.

Correct:

D. killall -HUP named

This command sends the SIGHUP (Hang Up) signal to all running processes named named (which is the BIND daemon). BIND is programmed to interpret SIGHUP as an instruction to reread its configuration file (named.conf) and all associated zone files. This is a common and graceful way to apply changes without fully stopping and starting the service.
E. rndc reload

rndc is the BIND Remote Name Daemon Control utility. The reload subcommand specifically instructs the named daemon to reread its configuration and zone files. This is the preferred and most granular way to achieve a reload, as it offers more control and better error reporting than sending raw signals with killall. You can also use rndc reload to reload a specific zone.
Incorrect:

A. named-checkzone -r

named-checkzone is a utility used to check the syntax and integrity of a DNS zone file before loading it into BIND. The -r option might specify a raw format, but regardless, this command only performs a check; it does not tell the running named daemon to reload anything.
B. killall named

When no signal is specified, killall sends the SIGTERM (terminate) signal. This signal politely requests the named process to shut down. It would stop the DNS server, not reload its configuration. To restart it, you would then need a separate command (e.g., systemctl start named or service named start). This causes service interruption.
C. rndc flush

rndc flush specifically clears the DNS server‘s cache. While reloading zones will also eventually refresh cached data related to those zones, rndc flush does not reload the zone files from disk. Its sole purpose is to clear the in-memory cache, forcing the server to perform new lookups for subsequent queries.

Correct:

B. allow-query
This is the standard and correct BIND named.conf option used to define which clients (specified by IP address, network prefix, or named ACL) are permitted to send DNS queries to the server. If this option is not specified, or if the client‘s IP is not in the allowed list, the server will not respond to their queries.
Incorrect:

A. accept-query

This is not a standard BIND configuration directive. While it sounds similar, the correct keyword is allow-query.
C. permit-query

This is not a standard BIND configuration directive. Similar to accept-query, it‘s a plausible but incorrect alternative.
D. query-group

This is not a standard BIND configuration directive. BIND uses Access Control Lists (ACLs) that can be named and then referenced by allow-query, but query-group itself is not a directive for query permission.
E. allowed-hosts

This is not a standard BIND configuration directive for controlling DNS queries. While allowed-hosts might be used in other service configurations (like Apache or SSH), it is not applicable to BIND‘s named.conf for query permissions.

Correct:

A. It tells BIND to look in the / home / sam / bind directory for its zone files.
This line, when found in the options section of /etc/named.conf as directory “/home/sam/bind“; (assuming the question implies the directory keyword which is almost always present), sets the working directory for the BIND daemon (named). When a zone file is referenced in named.conf without a full path (e.g., file “mylocal.zone“;), BIND will look for that file relative to this specified directory. Thus, it defines where BIND will find its zone files by default.
Incorrect:

B. It ensures that the sam user will be able to edit the BIND configuration.

The directory option in named.conf only sets BIND‘s working directory. It has no direct effect on the file system permissions for the sam user or their ability to edit configuration files. File permissions are controlled by standard Linux file system permissions.
C. It configures BIND to run as the sam user, thus improving the security of the server.

To configure BIND to run as a specific user, you would typically use the user directive in the options section (e.g., user named; or user sam;). The directory option only sets the working directory, not the user under which the daemon runs. While running as an unprivileged user (like named or a specially created user) improves security, this specific line does not achieve that.
D. It locks BIND in a chroot prison located in / home / sam / bind.

While BIND is often run in a chroot environment for security, the directory option alone does not implement a chroot jail. A chroot jail is typically set up by starting the named daemon with the -t option (e.g., named -t /home/sam/bind), or through systemd unit files that use RootDirectory=. The directory option defines the working directory within or outside the chroot, depending on how named is started. It does not initiate the chroot itself.

Correct:

A. CNAME

CNAME (Canonical Name) records are a standard and legal type of DNS record. They are used to create an alias from one domain name to another canonical (true) domain name. For example, http://www.example.com could be a CNAME for server1.example.com.
C. MX

MX (Mail Exchanger) records are a standard and legal type of DNS record. They are used to specify the mail server(s) responsible for accepting email for a particular domain. Each MX record includes a preference value, allowing for multiple mail servers to be listed with different priorities.
Incorrect:

B. ZF

ZF is not a standard or legal DNS record type. There is no such record type defined in DNS specifications.
D. DNS

DNS is not a standard or legal DNS record type. DNS is the acronym for the entire Domain Name System, not a specific record type within it. Common record types include A, AAAA, CNAME, MX, NS, PTR, SOA, TXT, SRV, etc.

Correct:

D. Using the allow-query statement {…;}; in the named configuration file.
This is the correct and standard BIND (named) configuration directive to control which hosts or networks are permitted to send DNS queries to the server. The allow-query statement is typically placed within the options block for global application or within individual zone blocks for specific zones. It takes an Access Control List (ACL) as an argument, which defines the allowed IP addresses or network prefixes. Any queries originating from sources not explicitly listed in the allow-query ACL (when one is defined) will be rejected.
Incorrect:

A. Using the answer {…;} statement; in the named configuration file.

There is no standard BIND configuration directive named answer. BIND uses directives like allow-query, allow-recursion, allow-transfer, etc., to control different types of access.
B. Using the answer only {…;} statement in the named configuration file.

Similar to option A, answer only is not a standard BIND configuration directive.
C. Using the query statement access {…;} in the named configuration file.

This is not a valid BIND configuration syntax or directive. While it contains relevant keywords like “query“ and “access,“ the structure and specific directive are incorrect.
E. Using the statement limit {…;}; in the named configuration file.

The limit statement exists in BIND, but it‘s used for resource limits (e.g., how many simultaneous queries, zones, or files can be open), not for controlling which hosts are permitted to query the server for domain name information.

Correct:

B. Run echo “nameserver 192.168.1.1“ >> /etc/resolv.conf

This command directly appends a line to the /etc/resolv.conf file, which is the standard configuration file on Linux clients for specifying DNS resolvers. The nameserver keyword followed by an IP address tells the system‘s resolver library which DNS server(s) to use for name lookups. The IP address in the option is 192.168.1.1, but assuming it should be 192.168.0.1 as per the question‘s premise, this is the correct method.
E. Add the 192.168.0.1 nameserver to /etc/resolv.conf

This is the conceptual explanation for option B. The fundamental way a Linux client is configured to use a specific DNS server is by listing its IP address(es) using the nameserver directive within the /etc/resolv.conf file. This file is read by the system‘s resolver library to find DNS servers.
Incorrect:

A. Run bind nameserver 192.168.1.1

bind is the name of the DNS server software (BIND), not a command-line utility for configuring client-side DNS. This command is syntactically incorrect and would not achieve the desired outcome.
C. Run ifconfig eth0 nameserver 192.168.0.1

ifconfig is used to configure network interfaces (like eth0), setting parameters such as IP addresses, netmasks, and MAC addresses. It does not have an option to directly configure DNS nameservers. DNS configuration is handled separately, usually via /etc/resolv.conf or network manager tools.
D. Run route add nameserver 192.168.0.1

The route command is used to manage the kernel‘s IP routing table. It adds or deletes routes to specific networks or hosts. It has no function related to configuring DNS nameservers. DNS server configuration is not a routing matter.

Correct:

E. http_access allow sales_net sales_time
This is the correct syntax and logic for http_access directives in Squid proxy server configuration (which is implied by the use of http_access and ACLs).
http_access: The directive for controlling HTTP access.
allow: The action to be taken if the following ACLs match.
sales_net: The first ACL to check. If the client‘s IP address matches the sales_net ACL, Squid proceeds to the next ACL.
sales_time: The second ACL to check. If the current time falls within the sales_time ACL, the entire line matches.
Squid processes http_access lines in order. When multiple ACLs are on the same line, they are combined with a logical AND. This means for the allow action to be taken, both sales_net and sales_time must match. This precisely meets the requirement: “users in the acl called ‘sales_net‘ must be allowed to access the Internet at the times specified in the time_acl called ‘sales_time‘.“
Incorrect:

A. http_access deny sales_time sales_net

This line would deny access if both sales_time and sales_net match, which is the opposite of the desired outcome (to allow access).
B. allow http_access sales_net sales_time

The allow keyword should come after http_access, as it‘s the action part of the directive, not the directive itself. The correct order is http_access [action] [acl1] [acl2] ….
C. http_access allow sales_net and sales_time

Squid‘s http_access directive uses implicit logical AND when multiple ACLs are listed on the same line. The explicit and keyword is not part of the http_access syntax. It would be a syntax error.
D. http_access sales_net sales_time

This line is missing the crucial action keyword (allow or deny). Without an action, the directive is incomplete and invalid.

Correct:

A. Prevent users from downloading files of a certain size.
reply_body_max_size in Squid limits the maximum size of the response body (i.e., the content of the file being downloaded, excluding headers) that Squid will retrieve and cache. If a file‘s content exceeds this limit, Squid will either stop downloading it or pass it directly to the client without caching, depending on other configurations. This is a direct way to control the size of files users can download through the proxy.
Incorrect:

B. Avoid overloading the cache_mem.

While reply_body_max_size can indirectly help manage cache usage by limiting what gets cached, its primary purpose is not to avoid overloading cache_mem (in-memory cache). cache_mem defines the maximum amount of RAM Squid will use for its in-memory cache, and cache_dir defines disk cache limits. Overloading cache_mem is typically managed by setting an appropriate cache_mem value itself and monitoring its usage, not by limiting individual reply body sizes. Large files are usually not cached in memory anyway, but directly streamed or written to disk cache.
C. Set a limit on the number of requests made to a single site by a single user.

This describes rate limiting or request throttling, which is typically controlled by ACLs and directives like delay_pools or specific per-user/per-site limits. reply_body_max_size has no relation to the number of requests.
D. Avoid attacks on the proxy server access port.

Attacks on the proxy server access port (e.g., port 3128 for HTTP) are mitigated by firewall rules, access control lists (http_access directives), and secure coding practices within Squid itself. Limiting the size of downloaded content (reply_body_max_size) does not prevent or mitigate attacks on the port itself.
E. Prevent the user from transmitting large video or audio files.

reply_body_max_size limits the size of downloads (responses from the server). It does not prevent users from transmitting (uploading) large files. Upload limits are typically managed by other directives or web server configurations. While video and audio files can be large, this option mischaracterizes the direction of the data flow controlled by reply_body_max_size.

Correct:

E. Reduce the size of cache_dir in the configuration file.
Explanation: Squid‘s cache_dir directive (e.g., cache_dir ufs /var/spool/squid 100 16 256) explicitly defines the location and maximum size of Squid‘s disk cache. Reducing the numeric value (e.g., changing 100 to 50 for 50MB) directly limits how much disk space Squid will consume for caching web objects. This is the most direct and effective way to reduce Squid‘s disk resource consumption.
Incorrect:

A. Rotate the log files regularly.

Explanation: Log file rotation (using tools like logrotate) manages the size of log files over time by archiving or deleting old logs. While this is crucial for overall system disk management and prevents log files from filling up a disk, it does not directly reduce Squid‘s cache disk resource consumption. The cache and logs are separate disk usage concerns.
B. Reduce the number of child processes to be started in the configuration file.

Explanation: Reducing the number of child processes (controlled by cache_peer_connect_timeout, workers, etc.) primarily affects CPU and RAM consumption, as well as the proxy‘s ability to handle concurrent connections. It does not directly impact the amount of disk space used for the cache.
C. Disable the registration of fully qualified domain names.

Explanation: This option doesn‘t correspond to a standard Squid configuration setting that directly impacts disk resource consumption. Squid needs to resolve FQDNs to IP addresses to function. Disabling or altering how it handles FQDNs wouldn‘t reduce disk usage; it would likely break functionality.
D. Disable the use of access lists.

Explanation: Access lists (acl and http_access directives) define who can access the proxy and what they can do. Disabling them would remove security and control over access but would not reduce disk cache consumption. In fact, if more traffic is allowed, the cache might even grow more (up to its defined cache_dir limit).

Correct:

A. Use iptables on your router to block traffic from all outgoing ports (port-80), except from the Proxy Server.

This is a common and effective method for enforcing proxy usage. By blocking direct outgoing HTTP traffic (port 80) from all hosts on the local network except the proxy server‘s IP, you force clients to use the proxy. If a client tries to connect directly to the internet on port 80, the router‘s firewall will block it, thus ensuring that the only path for HTTP traffic to the internet is through the proxy.
C. Use iptables on your router to redirect all outgoing ports (port-80) of traffic to the proxy server, except the proxy server itself.

This describes “transparent proxying.“ On the router (or gateway), iptables can be used with DNAT (Destination Network Address Translation) rules to intercept all outgoing traffic destined for port 80 and transparently redirect it to the proxy server‘s listening port (e.g., 3128 for Squid). Clients don‘t need to be explicitly configured to use the proxy; their requests are automatically forwarded. The exception for the proxy server itself is important to prevent a redirection loop for the proxy‘s own outgoing traffic.
Incorrect:

B. Use iptables on your proxy server to redirect all traffic from port 80 to the default port on the proxy server.

iptables on the proxy server itself would only affect traffic reaching the proxy server. If clients are not configured to send their traffic to the proxy in the first place, or if the router isn‘t forwarding traffic to it, rules on the proxy server won‘t force clients to use it for their internet access. This might be used for internal proxy configuration, but not for forcing all local network traffic through it from the client side.
D. Use iptables on your router to redirect all traffic to the proxy server to go to the Internet directly.

This statement is contradictory to the goal. Redirecting traffic to the proxy server to go to the Internet directly would bypass the proxy, which is the opposite of ensuring all access goes through the proxy. This would essentially undo any proxy configuration.

Correct:

D. openssl
openssl is the standard, multi-purpose command-line tool for working with SSL/TLS certificates, keys, and cryptographic functions on Linux and Unix-like systems. It is universally used to generate private keys and create Certificate Signing Requests (CSRs), which are then sent to a Certificate Authority (CA) to obtain an SSL/TLS certificate for an Apache (or any web) server to enable HTTPS.
Incorrect:

A. certgen

This is not a standard tool for generating certificates or CSRs. While some specific applications might have a utility with “certgen“ in its name, openssl is the generic and widely used command for this purpose in the Linux ecosystem.
B. apachectl

apachectl is a control script for the Apache HTTP Server. It‘s used to start, stop, restart, or check the syntax of Apache‘s configuration files. It does not have functionality to create cryptographic keys or CSRs.
C. csrtool

This is not a standard tool for creating CSRs. Like certgen, it‘s a plausible-sounding name but doesn‘t refer to a common Linux utility for this task.
E. httpsgen

This is not a standard tool for generating HTTPS-related files like keys or CSRs. openssl is the go-to utility.

Correct:

A. The client computer‘s IP address or host name.

Apache‘s access logs (typically access_log or access.log) record the IP address of the client that made the request. Depending on the LogFormat directive, this can sometimes be resolved to a hostname, though logging the raw IP is more common by default for performance reasons. This information is fundamental for understanding who is accessing the server.
D. The name of the browser claimed by the customer.

Apache‘s access logs, when configured with a common log format (like combined or a custom format including %u for user-agent), capture the User-Agent string sent by the client‘s web browser. This string typically identifies the browser type, version, and operating system. This is crucial for analytics and understanding client demographics.
Incorrect:

B. The route of network packets during the transfer.

Apache‘s access logs record application-level information about HTTP requests and responses. They do not record network-level details such as the specific hops (routers) that network packets traversed from the client to the server. This kind of information would be found using network diagnostic tools like traceroute or mtr, or by analyzing network packet captures (e.g., with tcpdump or Wireshark).
C. The size of the client‘s web browser window.

Apache access logs do not inherently record the dimensions of the client‘s web browser window. While some client-side JavaScript might capture this information and send it as part of a query string or custom header, it is not a standard piece of information logged by the Apache server itself. Server logs are generally concerned with the request and response, not client-side rendering details.