Q: In the vi editor, which command is used to save the current file without quitting, thereby remaining in the editing mode?

Introduction / Context: The vi editor in Unix/Linux is one of the most powerful text editors. A core skill is knowing how to save changes without exiting the editor. This helps when you want to preserve your work but continue editing further. Given Data / Assumptions: User is working in vi editor. Requirement is to save changes but remain in editing mode. Concept / Approach: Commands in vi begin with a colon (:) when in command mode. The :w command writes (saves) the file to disk but does not close it, allowing the user to continue editing. Step-by-Step Solution: Open vi with vi filename.txt.Make changes in insert mode, then press ESC to return to command mode.Type :w and press Enter.The editor reports “filename written” and remains open for editing. Verification / Alternative check: Compare :wq which saves and quits. Using only :w leaves you in vi to continue editing. Why Other Options Are Wrong: x: writes and exits. q!: quits without saving. :q: quits only if no changes are made. None of the above: incorrect because :w is correct. Common Pitfalls: Forgetting to press ESC before entering command mode. Confusing :w with :wq. Final Answer: :w.

Q: On a Unix/Linux system, which command is commonly used to see the services running on an NFS (Network File System) server?

Introduction / Context: NFS (Network File System) is widely used to share files across Unix/Linux systems. To troubleshoot or verify NFS service availability, administrators must know the command that lists running services. Given Data / Assumptions: The target is an NFS server. We want to list services registered with the RPC portmapper. Concept / Approach: The rpcinfo command queries the RPC bind (portmapper) service, which manages NFS services. By running rpcinfo -p servername, administrators can see ports and versions of NFS-related daemons. Step-by-Step Solution: Open terminal.Run rpcinfo -p localhost or rpcinfo -p nfsserver.View registered RPC services like nfs, mountd, status.Confirm NFS is active and ports are open. Verification / Alternative check: Cross-check with systemctl status nfs-server or showmount -e servername for exports. Why Other Options Are Wrong: serverinfo, NFSinfo, infserv: not valid Linux commands. None of the above: incorrect because rpcinfo is correct. Common Pitfalls: Running rpcinfo without -p lists nothing useful; always include -p. Confusing rpcinfo with showmount (which only shows shared exports). Final Answer: rpcinfo.

Q: By default, on which port does the Squid proxy server listen for incoming client requests?

Introduction / Context: Squid is a widely used proxy server for caching and filtering web traffic. One of the first steps in configuration or troubleshooting is knowing which TCP port it listens on by default. Given Data / Assumptions: The service in question is Squid proxy server. No custom configuration has been applied yet. Concept / Approach: By default, Squid listens on port 3128. This port is chosen historically and is distinct from port 80 (HTTP) or 443 (HTTPS). Administrators can change this value in the configuration file (squid.conf) if required. Step-by-Step Solution: Install squid package.Start service: systemctl start squid.Check default port: netstat -tulpn | grep squid or ss -ltnp.Confirm it listens on port 3128. Verification / Alternative check: Examine /etc/squid/squid.conf for http_port directive. Unless modified, it is set to 3128. Why Other Options Are Wrong: 4322, 2314, 7334: arbitrary numbers, not Squid defaults. None of the above: incorrect because 3128 is correct. Common Pitfalls: Confusing port 3128 with port 8080, which is sometimes used as an alternative proxy port. Assuming Squid listens on HTTP (80) by default—it does not. Final Answer: 3128.

Q: Linux desktop selection: Which utility lets you switch the default X Window desktop environment (for example, between GNOME and KDE) on certain Linux distributions?

Introduction / Context: Linux distributions that support multiple desktop environments often include a tool to change a user’s default X session without manually editing startup files. Historically, Red Hat–family systems provided switchdesk to toggle between GNOME, KDE, and other desktops. Given Data / Assumptions: You have multiple desktop packages installed. You want to change the default desktop for your X session. The distribution includes the switchdesk utility (or a similar tool). Concept / Approach: switchdesk updates the user’s desktop preference by writing the appropriate session or Xclients file. While modern distros may use display manager menus (GDM, SDDM, LightDM) at login, switchdesk remains a recognizable legacy tool for exam and certification contexts. Step-by-Step Solution: Ensure the target desktops (e.g., GNOME, KDE Plasma) are installed.Run switchdesk or switchdesk KDE (syntax varies) under your user account.Log out and log back in, or restart the display manager to apply changes.Alternatively choose the session from the display manager’s gear/options menu at login.Persist choice per user using the DM settings or ~/.Xclients if needed. Verification / Alternative check: After re-login, confirm the new desktop environment loads (desktop shell, panels, settings). Check ~/.Xclients or ~/.dmrc for updated entries on older systems. Why Other Options Are Wrong: b, c, d: intrc, xinitre, and Xchange are not standard tools for changing default desktops. e: Not applicable because switchdesk is an established utility for this purpose on certain distributions. Common Pitfalls: Expecting switchdesk on distributions that have deprecated it; forgetting that the display manager’s session chooser overrides defaults; lacking required desktop packages leading to fallback to a basic window manager. Final Answer: switchdesk

Question 1

On a Linux system, which command-line utility is used to access (connect to) a Windows/SMB network share?

Accepted Answer

Introduction / Context: Interoperability with Windows file sharing relies on the SMB/CIFS protocol. On Linux, the Samba suite provides tools to browse, connect to, and mount SMB shares. Choosing the correct client utility is crucial when you want to list shared resources or copy files to and from Windows servers from the terminal. Given Data / Assumptions: You need to interact with a remote SMB share (for example, //server/share). Administrative privileges are not strictly required just to list or copy files via the client. Samba tools are installed (for example, the 'samba-client' package). Concept / Approach: 'smbclient' is the interactive SMB/CIFS client similar to an FTP client. You can list shares, connect, and use commands like 'ls', 'get', and 'put'. For mounting an SMB share into the filesystem, 'mount -t cifs' (or 'mount.cifs') is used; however, the question asks for a command to access an SMB share, which fits 'smbclient' precisely. Step-by-Step Solution: List available shares: smbclient -L //server -U userConnect to a share: smbclient //server/share -U userTransfer files interactively: use 'get' to download and 'put' to uploadExit the session with 'quit' when finished Verification / Alternative check: As an alternative, test a mount: 'sudo mount -t cifs //server/share /mnt/share -o username=user'. Verify that the share becomes accessible under the mount point. Both approaches confirm SMB connectivity but 'smbclient' is the standalone tool for direct access without mounting. Why Other Options Are Wrong: NFS: A different protocol for Unix-like systems; not SMB. SMD: Not a valid tool in the Samba suite. smbserver: Not the correct client; Samba daemons are 'smbd' and 'nmbd'. None of the above: Incorrect because 'smbclient' is correct. Common Pitfalls: Confusing 'smbclient' (client) with 'smbd' (server daemon), and forgetting to include domain or workgroup in usernames when required (for example, DOMAIN\user or user@realm). Final Answer: smbclient

Question 2

In the vi (Vim) editor, which single-key Normal-mode command deletes exactly one character at the cursor position?

Accepted Answer

Introduction / Context: Mastering vi/Vim involves knowing concise Normal-mode commands for quick edits. Deleting a single character without entering Insert mode is a frequent operation when fixing typos or cleaning code, and there is a dedicated key for it. Given Data / Assumptions: You are in Normal mode (press Esc to ensure you are not inserting). The cursor is on the character to be deleted. You want to remove exactly one character without affecting surrounding text. Concept / Approach: The 'x' command deletes the character under the cursor. It can be prefixed by a count to delete multiple characters (for example, '3x' deletes three characters). Related commands include 'X' to delete the character to the left and 's' to substitute the character by entering Insert mode after deletion. Step-by-Step Solution: Press Esc to be in Normal mode.Place the cursor on the character to remove.Press x to delete that single character.Optionally repeat or use a count like 5x for five characters. Verification / Alternative check: Undo with 'u' to confirm exactly one character was affected. Compare with 'dl' (delete right), which achieves a similar effect; both operate at character granularity but 'x' is the canonical shortcut. Why Other Options Are Wrong: y: Yank (copy) text; it does not delete. a: Append after the cursor and enter Insert mode; no deletion. z: Scroll/center line operations; not deletion. None of the above: Incorrect because 'x' is correct. Common Pitfalls: Remaining in Insert mode and pressing 'x' results in literal typing of 'x'. Always ensure Normal mode before issuing motion/edit commands. Final Answer: x

Question 3

In classic PC partitioning (MBR), how many primary partitions can exist on a single physical drive?

Accepted Answer

Introduction / Context: Understanding legacy Master Boot Record (MBR) partitioning is still useful when maintaining older systems or preparing for certification exams. MBR imposes a specific layout and limits the number of primary partitions available per disk, a constraint that shaped common dual-boot and multi-OS strategies for decades. Given Data / Assumptions: The disk uses MBR (not GPT). You are counting only primary partitions as defined by the partition table format. Extended and logical partitions are considered separately from primary ones. Concept / Approach: MBR reserves a table with four entries for primary partitions. You can use all four as primary partitions, or consume one entry for an extended partition, inside which you may create multiple logical drives. This design is a workaround to the four-entry limit without modifying the original MBR specification. Step-by-Step Solution: Recognize MBR's fixed partition table with four slots.Decide layout: up to 4 primary partitions, or 3 primary + 1 extended.Place logical partitions inside the extended partition as needed.Apply tools (for example, fdisk) to view or edit the scheme. Verification / Alternative check: Use 'fdisk -l' on an MBR disk to see at most four entries flagged as primary/extended. On GPT disks, you will observe a different, more flexible scheme (often up to 128 partitions by default), confirming that the four-partition limit is unique to MBR. Why Other Options Are Wrong: 16/2/1: Do not match the MBR specification; these numbers can reflect logical partitions or unrelated limits. None of the above: Incorrect because the correct limit is four. Common Pitfalls: Confusing logical partitions within the extended area with primary partitions, and assuming GPT rules apply to legacy BIOS/MBR systems. Final Answer: 4

Question 4

For configuring the X Window System on legacy Linux distributions, which tool from the list is specifically the X-based graphical setup utility?

Accepted Answer

Introduction / Context: Before auto-configuration was common, administrators used setup tools to generate X server configuration files (for example, XF86Config). Some tools were text-mode dialogs, while others ran within X itself (graphical). Knowing which utility is X-based helps when an exam or legacy environment expects the historical distinction. Given Data / Assumptions: The context is XFree86-era tooling. We distinguish between graphical (X-based) and text/dialog-based utilities. Tool names are historically accurate: 'XF86Setup', 'XConfigurator' (Red Hat specific), and 'xf86config'. Concept / Approach: 'XF86Setup' is the X-based configuration program distributed with XFree86; it launches under the X server and presents graphical dialogs. By contrast, 'xf86config' is a text-mode, question-and-answer program. 'XConfigurator' (Red Hat) primarily provided text-based/newt dialogs rather than a true X-based GUI in most releases. Hence, among these options, only 'XF86Setup' is definitively the X-based tool. Step-by-Step Solution: Identify the requirement: X-based (graphical) configuration utility.Match tools to interfaces: XF86Setup → graphical; xf86config → text; XConfigurator → largely text/newt.Select XF86Setup as the correct answer.Note that modern systems prefer auto-detection or Xorg.conf.d snippets. Verification / Alternative check: Consult legacy XFree86 documentation showing screenshots and instructions for running 'XF86Setup'. Comparisons demonstrate that 'xf86config' runs fully in a terminal, confirming the interface difference. Why Other Options Are Wrong: XConfigurator: Historically a distribution tool with text-based dialogs; not strictly X-based. xf86config: Pure text-mode tool. All of the above: Incorrect because not all listed tools are X-based. Common Pitfalls: Assuming any tool with 'X' in the name is graphical, or confusing distribution-specific utilities with upstream XFree86 tools. Final Answer: XF86Setup

Question 5

In shell pattern matching (globbing), which wildcard matches any number of characters, including zero characters (that is, it can match an empty string)?

Accepted Answer

Introduction / Context: Command shells like bash and zsh expand wildcard patterns before executing commands. Understanding how each wildcard behaves prevents accidental file matches and enables precise selections when scripting or working interactively on large directories of files. Given Data / Assumptions: You are using standard POSIX-style globbing (not regular expressions). You want a pattern that can match an arbitrary-length sequence of characters, including none. Character classes and single-character wildcards are also available. Concept / Approach: The asterisk '' matches any string of characters, including the empty string. The question mark '?' matches exactly one character. Bracket expressions like '[ijk]' match exactly one character chosen from the set, and '[!ijk]' matches exactly one character not in the set. Therefore, only '' satisfies the requirement of matching zero or more characters. Step-by-Step Solution: Match all files: ls Match all .txt files: ls .txt (matches .txt and may include 'file.txt')Match files starting with chap: ls chapDemonstrate empty match: echo XY matches 'XY' if no characters occur between Verification / Alternative check: Use 'printf '%s
' ' in an empty directory and observe that shells may pass the literal '' if 'nullglob' is not set; with 'nullglob' enabled, the pattern expands to nothing. This illustrates shell options but does not change the semantic that '' can match zero characters in principle. Why Other Options Are Wrong: ? : Matches exactly one character, not zero-or-more. [ijk] : Matches one character from the set i, j, or k. [!ijk] : Matches one character that is not i, j, or k. None of the above: Incorrect because '' is correct. Common Pitfalls: Confusing shell globs with regular expressions, and forgetting that some shells require options like 'nullglob' for empty expansions to vanish instead of leaving a literal asterisk. Final Answer: *

Question 6

Which command can you execute to count only the number of lines in a file on Unix/Linux?

Accepted Answer

Introduction / Context: Counting lines is a frequent need when validating datasets, logs, or configuration files. Unix/Linux provides a compact utility that can report multiple metrics, and with the right switch it outputs exactly the line count, making it convenient for scripting and quick checks. Given Data / Assumptions: You have a text file and want the total number of lines. Only standard POSIX tools are assumed. Output format should be script-friendly if needed. Concept / Approach: The 'wc' (word count) utility prints lines, words, and bytes. By passing the '-l' option, 'wc' restricts output to the line count. You can supply one or more filenames; with multiple files, it prints per-file counts plus a total. In pipelines, 'wc -l' counts the number of input lines from standard input. Step-by-Step Solution: Count lines in file: wc -l filenameCount lines from a pipeline: grep ERROR app.log | wc -lSuppress filename in output: wc -l < filenameCount lines across multiple files: wc -l file1 file2 Verification / Alternative check: Use 'awk 'END{print NR}' filename' or 'nl -ba filename | tail -n 1' to confirm the same count. For binary or huge files, ensure the input has newline-terminated records to avoid off-by-one expectations. Why Other Options Are Wrong: lc / cl / count: Not standard Unix commands. None of the above: Incorrect because 'wc -l' is the exact tool for line counts. Common Pitfalls: Assuming bytes equal characters in multi-byte encodings (irrelevant for line counts) and forgetting input redirection when you do not want the filename echoed with the count. Final Answer: wc -l

Question 7

Within the OSI networking model, which statement correctly describes the responsibility of the Physical layer (Layer 1)?

Accepted Answer

Introduction / Context: The OSI reference model separates networking into layered responsibilities. Accurately mapping functions to layers helps in protocol analysis and troubleshooting. The Physical layer is the foundation, dealing with raw bit transmission and hardware signaling, while upper layers handle framing, addressing, routing, and reliability. Given Data / Assumptions: Layer numbering goes from 1 (Physical) up to 7 (Application). We must select the statement that matches Layer 1 duties. Terminology such as frames and packets refers to upper layers. Concept / Approach: The Physical layer defines electrical, mechanical, and procedural interfaces for transmitting bits. This includes voltage levels, timing, modulation, connector pinouts, optical wavelengths, and radio characteristics. Data Link (Layer 2) builds frames and provides error detection/correction, while Network (Layer 3) constructs packets and performs routing. Therefore, only the statement about electrical characteristics aligns with Layer 1. Step-by-Step Solution: Identify key terms: 'electrical characteristics', 'frames', 'packets'.Map to layers: electrical → L1; frames/error control → L2; packets/routing → L3.Eliminate statements that belong to higher layers.Select the Physical layer responsibility regarding signaling characteristics. Verification / Alternative check: Consult examples: Ethernet PHY chips, fiber-optic transceivers, RJ-45 pinouts, and Wi-Fi radio parameters are Physical layer topics. CRC checks and MAC addressing belong to Data Link, while IP addressing and routing belong to Network—confirming the layer separation. Why Other Options Are Wrong: Constructs packets and sends them: That is a Network layer (and partially lower) responsibility; not Physical. Controls error detection/correction: Primarily Data Link layer. All of the above: False because only one statement matches Layer 1. None of the above: False because one statement is correct. Common Pitfalls: Confusing 'bits on the wire' (L1) with framing (L2) and packet delivery (L3), and assuming error correction is always handled at the physical level—it is generally handled in L2 and above in the OSI model context. Final Answer: Defines the electrical characteristics of signals passed between the computer and communication devices

Question 8

In the vi editor, which command is used to save the current file without quitting, thereby remaining in the editing mode?

Accepted Answer

Introduction / Context: The vi editor in Unix/Linux is one of the most powerful text editors. A core skill is knowing how to save changes without exiting the editor. This helps when you want to preserve your work but continue editing further. Given Data / Assumptions: User is working in vi editor. Requirement is to save changes but remain in editing mode. Concept / Approach: Commands in vi begin with a colon (:) when in command mode. The :w command writes (saves) the file to disk but does not close it, allowing the user to continue editing. Step-by-Step Solution: Open vi with vi filename.txt.Make changes in insert mode, then press ESC to return to command mode.Type :w and press Enter.The editor reports “filename written” and remains open for editing. Verification / Alternative check: Compare :wq which saves and quits. Using only :w leaves you in vi to continue editing. Why Other Options Are Wrong: x: writes and exits. q!: quits without saving. :q: quits only if no changes are made. None of the above: incorrect because :w is correct. Common Pitfalls: Forgetting to press ESC before entering command mode. Confusing :w with :wq. Final Answer: :w.

Question 9

On a Unix/Linux system, which command is commonly used to see the services running on an NFS (Network File System) server?

Accepted Answer

Introduction / Context: NFS (Network File System) is widely used to share files across Unix/Linux systems. To troubleshoot or verify NFS service availability, administrators must know the command that lists running services. Given Data / Assumptions: The target is an NFS server. We want to list services registered with the RPC portmapper. Concept / Approach: The rpcinfo command queries the RPC bind (portmapper) service, which manages NFS services. By running rpcinfo -p servername, administrators can see ports and versions of NFS-related daemons. Step-by-Step Solution: Open terminal.Run rpcinfo -p localhost or rpcinfo -p nfsserver.View registered RPC services like nfs, mountd, status.Confirm NFS is active and ports are open. Verification / Alternative check: Cross-check with systemctl status nfs-server or showmount -e servername for exports. Why Other Options Are Wrong: serverinfo, NFSinfo, infserv: not valid Linux commands. None of the above: incorrect because rpcinfo is correct. Common Pitfalls: Running rpcinfo without -p lists nothing useful; always include -p. Confusing rpcinfo with showmount (which only shows shared exports). Final Answer: rpcinfo.

Question 10

By default, on which port does the Squid proxy server listen for incoming client requests?

Accepted Answer

Introduction / Context: Squid is a widely used proxy server for caching and filtering web traffic. One of the first steps in configuration or troubleshooting is knowing which TCP port it listens on by default. Given Data / Assumptions: The service in question is Squid proxy server. No custom configuration has been applied yet. Concept / Approach: By default, Squid listens on port 3128. This port is chosen historically and is distinct from port 80 (HTTP) or 443 (HTTPS). Administrators can change this value in the configuration file (squid.conf) if required. Step-by-Step Solution: Install squid package.Start service: systemctl start squid.Check default port: netstat -tulpn | grep squid or ss -ltnp.Confirm it listens on port 3128. Verification / Alternative check: Examine /etc/squid/squid.conf for http_port directive. Unless modified, it is set to 3128. Why Other Options Are Wrong: 4322, 2314, 7334: arbitrary numbers, not Squid defaults. None of the above: incorrect because 3128 is correct. Common Pitfalls: Confusing port 3128 with port 8080, which is sometimes used as an alternative proxy port. Assuming Squid listens on HTTP (80) by default—it does not. Final Answer: 3128.

Question 11

Linux server interoperability: During custom installation or configuration, which package group enables a Linux machine to share files and printers with Windows clients using SMB/CIFS?

Accepted Answer

Introduction / Context: Cross-platform file and printer sharing is common in mixed environments. Windows clients use the SMB/CIFS protocol. On Linux/UNIX, Samba implements SMB/CIFS, allowing seamless participation in Windows workgroups or Active Directory domains. Given Data / Assumptions: Linux system needs to communicate with Windows clients using standard Windows file/print sharing. Custom install screens present grouped package selections. Networking is properly configured (IP address, routing, DNS). Concept / Approach: The correct feature set is provided by Samba (often labeled “SMB (Samba) Connectivity”). Samba includes smbd and nmbd (or winbindd) for file/print services and domain integration. Alternatives like IPX/NetWare support are for older Novell NetWare networks, while Dial-up Workstation relates to PPP/Modem connectivity, not SMB. Step-by-Step Solution: Select the Samba/SMB package group during installation or install later via your package manager.Configure /etc/samba/smb.conf to define shares, workgroup/domain, and access controls.Start and enable Samba services (for example, systemctl enable --now smb nmb or smb.service).Create or map user accounts and set Samba passwords (for example, smbpasswd -a username).Test from a Windows client with \servername\sharename. Verification / Alternative check: Use smbclient -L //server -U user to list shares. Confirm browsing/printing from Windows. Check firewall rules (ports 137–139, 445) and SELinux contexts where applicable. Why Other Options Are Wrong: b: IPX/NetWare Connectivity supports NetWare, not Windows SMB/CIFS. c: Dial-up Workstation focuses on modem-based remote connectivity, not LAN file sharing. d: Only SMB connectivity is needed; the others do not enable Windows SMB file/print sharing. Common Pitfalls: Forgetting to align Linux and Windows time sources (Kerberos/AD joins are time-sensitive); neglecting firewalls; mismatching workgroup/domain names; overlooking file permissions and SELinux labeling of share paths. Final Answer: SMB (Samba) Connectivity

Question 12

Linux desktop selection: Which utility lets you switch the default X Window desktop environment (for example, between GNOME and KDE) on certain Linux distributions?

Accepted Answer

Introduction / Context: Linux distributions that support multiple desktop environments often include a tool to change a user’s default X session without manually editing startup files. Historically, Red Hat–family systems provided switchdesk to toggle between GNOME, KDE, and other desktops. Given Data / Assumptions: You have multiple desktop packages installed. You want to change the default desktop for your X session. The distribution includes the switchdesk utility (or a similar tool). Concept / Approach: switchdesk updates the user’s desktop preference by writing the appropriate session or Xclients file. While modern distros may use display manager menus (GDM, SDDM, LightDM) at login, switchdesk remains a recognizable legacy tool for exam and certification contexts. Step-by-Step Solution: Ensure the target desktops (e.g., GNOME, KDE Plasma) are installed.Run switchdesk or switchdesk KDE (syntax varies) under your user account.Log out and log back in, or restart the display manager to apply changes.Alternatively choose the session from the display manager’s gear/options menu at login.Persist choice per user using the DM settings or ~/.Xclients if needed. Verification / Alternative check: After re-login, confirm the new desktop environment loads (desktop shell, panels, settings). Check ~/.Xclients or ~/.dmrc for updated entries on older systems. Why Other Options Are Wrong: b, c, d: intrc, xinitre, and Xchange are not standard tools for changing default desktops. e: Not applicable because switchdesk is an established utility for this purpose on certain distributions. Common Pitfalls: Expecting switchdesk on distributions that have deprecated it; forgetting that the display manager’s session chooser overrides defaults; lacking required desktop packages leading to fallback to a basic window manager. Final Answer: switchdesk

Question 13

Network services registry: On UNIX/Linux systems using inetd (or xinetd historically), which file lists service names and their corresponding TCP/UDP port numbers?

Accepted Answer

Introduction / Context: Classic UNIX networking stacks map human-readable service names (like http, smtp, ssh) to well-known port numbers. System libraries consult a canonical file for these mappings, enabling tools and daemons to specify services symbolically. Given Data / Assumptions: The host uses traditional name service files in /etc. inetd/xinetd or network libraries resolve service-to-port mappings from a local database. No special name service switch overrides are considered. Concept / Approach: The file /etc/services lists services with their port/protocol pairs (for example, ssh 22/tcp). C library functions like getservbyname consult this database. While many systems now prefer systemd socket activation or stand-alone daemons, /etc/services remains the canonical reference for service names and ports. Step-by-Step Solution: Open /etc/services to view mappings such as ftp 21/tcp and http 80/tcp.Confirm a service by running getent services ssh (where supported).Use netstat or ss to correlate listening ports with service names.Update custom services locally by appending new entries if needed (avoid conflicts).Coordinate with firewall rules to allow or block corresponding ports. Verification / Alternative check: Check nsswitch behavior in /etc/nsswitch.conf to ensure the services database is consulted locally. Validate resolution using getent services servicename. Why Other Options Are Wrong: b: /etc/nsorder is not standard across modern systems. c: /etc/nsswitch.conf configures name service lookup order; it does not list service-port pairs. d: /etc/hosts maps hostnames to IP addresses, not ports. e: Not applicable because /etc/services is correct. Common Pitfalls: Confusing service names with daemon binary names; assuming /etc/services changes active daemon ports (it is informational, not authoritative for running daemons); forgetting protocol distinctions (tcp vs udp). Final Answer: /etc/services

Question 14

OSI model fundamentals: Which OSI layer provides services for end-user applications, including authentication, resource sharing, file transfer, and network management features?

Accepted Answer

Introduction / Context: The OSI reference model separates networking responsibilities into seven layers, clarifying where functions such as reliability, encryption, session control, and user-facing services belong. Correctly placing capabilities like file transfer and authentication helps diagnose issues and design protocols. Given Data / Assumptions: We are using the standard 7-layer OSI model. User/application support features are mentioned: passwords (authentication), resource sharing, file transfer, and network management. We must identify the appropriate layer. Concept / Approach: Layer 7, the Application layer, interfaces directly with applications and end users. It provides services like HTTP, FTP, SMTP, SNMP, and related mechanisms for authentication, resource discovery, and management. Layer 6 (Presentation) focuses on data representation (encryption, compression, translation), and Layer 5 (Session) manages dialog control and synchronization. Layer 4 (Transport) provides end-to-end reliability and flow control. Step-by-Step Solution: Identify the features listed (file transfer, resource sharing, user authentication, management).Map these to known Application layer protocols (FTP for file transfer, SMB at the application suite level, SNMP for management).Confirm that lower layers provide supporting functions rather than user-facing services.Choose Layer 7 as the layer delivering these services to applications.Validate by checking common protocol classifications in OSI teaching material. Verification / Alternative check: Look up protocol-to-layer mappings: HTTP/FTP/SMTP/SNMP are cited as Application layer protocols. Verify that Transport (Layer 4) concerns segments and reliability, not user services. Why Other Options Are Wrong: a: Layer 4 focuses on transport (TCP/UDP), not user/application services. b: Layer 5 coordinates sessions but does not implement file transfer itself. c: Layer 6 handles syntax/semantics (encryption/encoding), not end-user application services. e: Not applicable because Layer 7 is correct. Common Pitfalls: Confusing Presentation (encryption/compression) with Application services; assuming Session performs authentication universally; forgetting that OSI is a model, while real-world TCP/IP stacks may merge layers functionally. Final Answer: Layer 7 protocols

Question 15

User identity queries in UNIX: Which command displays information about the current user in a human-friendly form (commonly showing login name, terminal, and time)?

Accepted Answer

Introduction / Context: When working on multi-user UNIX systems, it is useful to confirm which account you are using and the terminal or remote session you occupy. Multiple commands provide identity or environment information, and choosing the right one depends on what detail you need. Given Data / Assumptions: You want a readable summary of your login identity and terminal. You are in a typical shell session (local or remote). Standard userland utilities are available. Concept / Approach: The who command reports logged-in users. With the am i arguments, it returns details of the current session: username, terminal, login time, and possibly source host. Alternatives like id print UIDs/GIDs numerically, and pwd prints the present working directory, not user identity. which only locates executables in PATH. Step-by-Step Solution: Run who am i in the shell.Read the output fields: username, TTY/PTS, login time, optional remote host.Use id for UID/GID details if needed (id -un for username only).Combine with tty to see the device file for your terminal.Use who -m (on some systems) as an equivalent to who am i. Verification / Alternative check: Compare who am i output with environment variables like $USER and $LOGNAME, and with id -un for consistent identity information. On SSH, check last or w for session history and current processes. Why Other Options Are Wrong: a: which shows where a command binary resides, not user identity. b: pwd prints your current directory path. c: i /4 is not a standard UNIX command. e: Not applicable because who am i is correct for user/session info. Common Pitfalls: Assuming $USER always reflects effective UID; in sudo contexts, id and who may reflect different identities; misreading who output fields when connected via remote TTYs. Final Answer: who am i

Question 16

File rename operation in UNIX: Which command is used to rename a file (and can also move it between directories)?

Accepted Answer

Introduction / Context: In UNIX/Linux, file manipulation is performed by a small set of powerful commands. Renaming a file is conceptually the same as moving it within the same filesystem to a new name. The mv utility handles both rename and move actions. Given Data / Assumptions: You need to rename a file within the same directory or move it to a different directory. There are no filesystem permission issues preventing rename/move. No special DOS/Windows commands are available (pure UNIX environment). Concept / Approach: mv old new renames a file to a new name in the same directory. mv file dir/ moves a file to another directory, optionally changing the name (dir/new). Unlike copy, mv does not duplicate data; it updates directory entries. Across filesystems, mv effectively performs a copy-and-remove under the hood. Step-by-Step Solution: To rename: mv report.txt report_old.txtTo move (same name): mv report.txt archive/To move and rename: mv report.txt archive/report_2025.txtUse -i to prompt before overwriting an existing destination.Use -v for verbose output during batch operations. Verification / Alternative check: Run ls or stat on the destination path to confirm the new name and location. When moving large files across filesystems, monitor disk usage to verify the copy-and-remove succeeded. Why Other Options Are Wrong: a: ren is a DOS/Windows command, not standard on UNIX. c: remove is not the UNIX command (rm deletes files). d: change is not a UNIX file utility. e: Not applicable because mv is correct. Common Pitfalls: Overwriting existing files without -i; moving across filesystems unexpectedly (which can be slow); attempting to rename files without proper write permissions on the directory. Final Answer: mv

Question 17

Linux/UNIX filesystem basics  Which directory on a typical Linux system contains many system administrator executables and related system-management tools (alongside some configuration locations elsewhere)?

Accepted Answer

Introduction / Context: The Linux/UNIX filesystem is organized by role. Understanding where administrative commands and configuration live helps with troubleshooting, scripting, and security hardening. While configuration files are generally in /etc, many privileged system-management binaries are in /sbin (and /usr/sbin). Knowing the distinction prevents accidental edits in the wrong place and enables faster navigation during maintenance or recovery. Given Data / Assumptions: The question asks for the location of system administrator executables and related tools. Single best answer among core top-level directories: /home, /proc, /var, /sbin. Standard Filesystem Hierarchy Standard (FHS) conventions apply. Concept / Approach: /sbin holds system binaries primarily intended for the superuser (root): boot utilities, network configuration tools, filesystems administration, and recovery commands. These differ from ordinary user commands in /bin and site-wide apps in /usr/bin. System configuration files (text) are mostly under /etc, but the executables used to apply or manage those configurations live in /sbin or /usr/sbin. Step-by-Step Solution: Identify directory purpose: /sbin = system administration executables.Contrast with /etc, which stores configs, not offered as an option.Exclude other options based on their roles.Select the directory that best matches administrative binaries: /sbin. Verification / Alternative check: Run which ip or which fsck on a Linux host; results typically point to /usr/sbin or /sbin, confirming admin-binary locations. Reading the FHS documentation further reinforces this mapping. Why Other Options Are Wrong: /home stores user home directories, not admin executables./proc is a virtual filesystem exposing kernel and process state./var contains variable data like logs, spool, and caches, not core admin binaries. Common Pitfalls: Confusing /etc (configs) with /sbin (binaries). Assuming /usr/sbin and /sbin are interchangeable across all distros without PATH considerations. Running admin tools without root privileges and expecting success. Final Answer: /sbin

Question 18

Linux installation methods  Which types of Linux installations typically require a special boot disk or boot image because additional drivers (for networking or laptop controllers) are needed to start the installer?

Accepted Answer

Introduction / Context: Historically, many Linux distributions supported installations over the network or on laptops with PCMCIA controllers. In such cases, the standard boot media sometimes lacked the necessary network or controller drivers. A dedicated boot disk or specialized boot image was used to load those drivers and bring up the installer environment. Given Data / Assumptions: NFS or FTP installations require networking drivers early in the boot process. PCMCIA (common in older laptops) requires controller support before storage or network devices are usable. The question asks which install types typically need a special boot disk/image. Concept / Approach: When the installer must access network shares (NFS/FTP) or PCMCIA-attached devices, it needs appropriate kernel modules very early. Distributions provided “network/PCMCIA boot disks” or “netinst” images to initialize hardware before the full installer ran. Step-by-Step Solution: Recognize NFS and FTP installs demand early network initialization.Note that PCMCIA controllers also need early driver loading.Therefore, a special boot disk/image is common to all three scenarios.Choose the inclusive answer. Verification / Alternative check: Review historical documentation for classic distros (e.g., Debian netinst, Red Hat boot images) that shipped separate boot media for network and PCMCIA installs. Why Other Options Are Wrong: NFS only (Option A) omits FTP and PCMCIA needs.FTP only (Option B) omits NFS/PCMCIA.PCMCIA only (Option C) omits network-based installs. Common Pitfalls: Assuming modern USB installers never need extra drivers; some hardware still requires special initrds. Confusing repository access after install with pre-install driver needs. Not verifying network hardware compatibility before choosing a net install. Final Answer: All of the above

Question 19

IPv4 classful addressing (legacy concept)  Which IPv4 address class historically suited a very small number of networks with a very large number of hosts (nodes) per network?

Accepted Answer

Introduction / Context: Before Classless Inter-Domain Routing (CIDR), IPv4 used classful addressing with Classes A, B, and C to divide the address space. Each class traded off the number of available networks against the number of hosts per network. Understanding the legacy model helps interpret older documentation and exam questions, even though modern networks use CIDR. Given Data / Assumptions: Class A, B, C differ in network vs. host bits. We seek the class with very few networks but very many hosts per network. Historical ranges: A (0–127), B (128–191), C (192–223) in first octet. Concept / Approach: Class A allocated 8 bits for the network (7 usable) and 24 bits for hosts, yielding a tiny number of networks but roughly 16 million host addresses per network (theoretical). Class B balanced both, and Class C offered many networks with few hosts per network. Step-by-Step Solution: Identify the class with maximum host bits: Class A has 24 host bits.Recognize this implies very large host capacity per network.A consequence is a small count of networks compared to Classes B and C.Therefore select Class A. Verification / Alternative check: Compare: Class B has 16 bits host portion (~65,534 hosts). Class C has 8 bits host portion (~254 hosts). This confirms Class A is the intended answer. Why Other Options Are Wrong: Class B balances networks and hosts; not “very few networks.”Class C provides many small networks; opposite of the requirement.All of the above is invalid because the property uniquely matches Class A. Common Pitfalls: Confusing modern CIDR with legacy classes. Assuming private address ranges (10.0.0.0/8) define the class behavior; they are examples within the classful scheme. Forgetting that network and broadcast addresses reduce usable host counts slightly. Final Answer: Class A

Question 20

Linux FTP access control  In which configuration file can a Linux administrator list user accounts that are not allowed to log in via FTP service?

Accepted Answer

Introduction / Context: FTP services on UNIX/Linux historically used a deny-list file to prevent certain user accounts from authenticating over FTP. This is important for hardening systems, as accounts such as root, daemon, or system service users should never have FTP access. Given Data / Assumptions: Classic FTP daemons (e.g., wu-ftpd, vsftpd in some modes) recognize a local deny list. We need the specific file used to list users denied FTP access. System uses standard locations rather than custom builds. Concept / Approach: /etc/ftpusers traditionally contains a newline-separated list of usernames not permitted to log in via FTP. Although different FTP daemons may have additional files (like /etc/ftpaccess) for broader policy, /etc/ftpusers is the canonical deny list for user-based restrictions. Step-by-Step Solution: Recall that /etc/ftpusers is a deny list of accounts.Recognize that /etc/hosts.deny is part of TCP Wrappers, controlling host-level access, not specific FTP usernames.Note that /etc/ftpaccess configures broader FTP behaviors and permissions, not the simple deny list.Select /etc/ftpusers. Verification / Alternative check: Check your FTP daemon documentation. Many examples ship with /etc/ftpusers containing root, bin, daemon, and similar non-login accounts by default. Why Other Options Are Wrong: /etc/hosts.deny controls hosts via TCP Wrappers, not user lists./etc/ftpaccess provides general FTP configuration but not specifically the user deny list.All of the above cannot be correct because only one file is the standard deny list. Common Pitfalls: Forgetting that vsftpd may also use /etc/vsftpd/user_list with allow/deny semantics; always check daemon-specific docs. Assuming disabling shell access also disables FTP; they are separate. Leaving sensitive accounts enabled by default. Final Answer: /etc/ftpusers

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