Question 1

In Unix/Linux file management, which command is used to remove (delete) one or more files from the filesystem?

Accepted Answer

Introduction / Context: Removing files safely and correctly is a fundamental shell skill. The standard POSIX command for deleting files is short and powerful, supporting interactive prompts, recursive removal for directories, and forceful deletion when required. Knowing the right command prevents confusion with DOS/Windows terminology. Given Data / Assumptions: We are operating in a Unix-like shell (bash, zsh, etc.). Target objects are regular files (not necessarily directories). Standard GNU coreutils or equivalent are available. Concept / Approach: The command 'rm' removes directory entries for files. Common switches include '-i' for interactive confirmation, '-f' to force and ignore nonexistent files, and '-r' (or '-R') to recurse into directories. Deletion is immediate; recovery relies on backups or snapshots, so caution is advised, especially with wildcards and elevated privileges. Step-by-Step Solution: Delete a single file: rm file.txtDelete multiple files: rm *.logPrompt before each removal: rm -i *.confRemove a directory tree: rm -r old_project/ (optionally add -i) Verification / Alternative check: Run 'ls' after the command to confirm the files are gone. For critical data, simulate first with 'echo rm ...' to ensure globbing expands as expected before committing the real removal. Why Other Options Are Wrong: erase/delete: DOS/Windows commands; not standard on Unix. dm: Not a standard deletion command. None of the above: Incorrect because 'rm' is the correct Unix command. Common Pitfalls: Using 'rm -rf /' style destructive commands, forgetting that 'rm' does not use a trash can, and not quoting filenames with spaces or special characters. Final Answer: rm

Question 2

In the context of X Window System development, which project (from the options listed) is historically known for developing and distributing the X server on common PC hardware?

Accepted Answer

Introduction / Context: The X Window System provides the network-transparent graphical foundation used by many Unix-like environments. Over the years, several organizations have contributed, but historically on PCs the XFree86 Project was the well-known distributor and developer of the X server supporting a wide array of video hardware. Understanding this history helps when reading legacy documentation and certification materials. Given Data / Assumptions: The question refers to historical/legacy context. Options include various open-source groups that focus on different layers of the Linux desktop stack. We must identify the one tied to the X server implementation on commodity PCs. Concept / Approach: XFree86 Project, Inc. produced widely used releases of the X server tailored to x86 and compatible hardware through the 1990s and early 2000s. While modern systems commonly use the X.Org Server (a fork led by the X.Org Foundation), that choice is not listed among the options. RHAD Labs (an early Red Hat Advanced Development group) and the GNOME Project primarily focused on desktop environments, libraries, and applications—not on the core X server itself. Step-by-Step Solution: Identify the component in question: the X server (display server).Match to organizations with historical responsibility for PC support.Select XFree86 Project, Inc. as the best match among given choices.Note that contemporary distributions commonly ship X.Org (not offered in the options). Verification / Alternative check: Consult legacy Linux distribution release notes from the era; they reference XFree86 versions and drivers for chipsets from S3, ATI, Matrox, and others, confirming XFree86's role in X server distribution on PCs. Why Other Options Are Wrong: RHAD Labs: Known for development of tools and technologies at Red Hat, not the X server core. GNOME Project: Maintains a desktop environment that runs on top of X; it does not implement the X server itself. All of the above: Incorrect because only one organization directly maintained the server. None of the above: Incorrect since XFree86 is a direct, valid answer. Common Pitfalls: Confusing the display server (X) with desktop environments (GNOME/KDE) or assuming today's X.Org Foundation is the only answer historically relevant. Final Answer: XFree86 Project, Inc.

Question 3

On Unix/Linux, which of the following is not a user-to-user communication or messaging-related command?

Accepted Answer

Introduction / Context: Unix-like systems historically provide several terminal-based tools for real-time or near-real-time communication between users. Distinguishing these tools from general text-processing utilities is important in both administration and user support contexts. Given Data / Assumptions: We focus on classic shell commands available on multi-user systems. Communication involves messaging to terminals or sending email. One choice is a text-search utility, not a communication command. Concept / Approach: mail sends electronic mail. write sends a live message to another user's terminal (TTY). mesg toggles whether a user's terminal permits such messages ('mesg y/n'). In contrast, grep searches for patterns in text and has nothing to do with inter-user communication. Therefore, the non-communication command is grep. Step-by-Step Solution: List communication tools: mail, write, mesg.Identify their purpose: email, instant terminal messaging, permission control.Recognize grep as a pattern-matching tool used for filtering text.Select grep as the odd one out (not communication). Verification / Alternative check: Run 'man grep' to confirm it is a text filter. Compare with 'man write' and 'man mesg' to see their roles in messaging and permissions. Testing 'write username' demonstrates real-time delivery on the target TTY if 'mesg y' is set. Why Other Options Are Wrong: mail: Email tool; clearly communication-related. mesg: Controls terminal message permissions; part of the communication workflow. write: Sends direct terminal messages to logged-in users. None of the above: Incorrect because one option (grep) is indeed not a communication tool. Common Pitfalls: Assuming 'mesg' sends messages (it does not; it toggles permissions), or thinking 'grep' interacts with users because it can read from stdin—it only filters text. Final Answer: grep

Question 4

Which command pattern below would not correctly list exactly the files chap01, chap02, and chap04 in a Unix/Linux shell?

Accepted Answer

Introduction / Context: Shell globbing expands wildcard patterns to matching filenames. Bracket expressions like [124] select specific characters at a given position, while matches any string (including none). Understanding where and how to use these patterns is critical for selecting the intended files and avoiding accidental matches or omissions. Given Data / Assumptions: The existing files of interest are named: chap01, chap02, chap04. Other similar files (for example, chap03) may exist alongside them. We evaluate which pattern does not list those specific files. Concept / Approach: ls chap0[124] matches filenames beginning with 'chap0' and ending with 1, 2, or 4. It correctly selects chap01, chap02, and chap04. ls chap lists every name starting with 'chap', which includes the three targets (though not exclusively). In contrast, ls chap[124] looks for filenames with exactly five characters where the fifth character is 1, 2, or 4 (for example, chap1, chap2). It does not match chap01, chap02, or chap04 because those have six characters with a zero between 'chap' and the final digit. Therefore, that pattern fails to list the required files. Step-by-Step Solution: Check desired form: chap0X where X in {1,2,4}.Pattern that works: chap0[124] ➜ matches exactly chap01, chap02, chap04.Broad pattern: chap* ➜ includes all chap* files (superset, but still lists the three).Incorrect pattern: chap[124] ➜ matches chap1/chap2/chap4, not chap0X. Verification / Alternative check: Run 'printf "%s
" chap*' in a test directory and compare expansions for each pattern. Observe that chap[124] never includes the '0' required for chap0[124]. Why Other Options Are Wrong: ls chap*: Although it lists extra files, it still lists the three target files. ls chap0[124]: Precisely matches the three names. ls - x chap0[124]: Interpreted (typo aside) as an '-x' option with the same matching set; it still lists the targeted files on many systems. Common Pitfalls: Forgetting that bracket expressions match a single character, misplacing the '0', or assuming globbing uses regex rules like '?' and '+'—shell globs are simpler and differ from regular expressions. Final Answer: ls chap[124]

Question 5

Historically in Red Hat Linux, which hardware architecture from the list below was not supported as a primary target platform?

Accepted Answer

Introduction / Context: Linux distributions have varied widely in the hardware architectures they support. Red Hat historically focused on specific platforms that matched its commercial goals. Knowing which platforms were primary targets helps interpret legacy installation guides and certification items that refer to architecture support. Given Data / Assumptions: The context is legacy Red Hat Linux (pre–RHEL era), not modern Fedora or community remixes. Options list several well-known CPU/platform architectures. We want the item not supported as a primary Red Hat platform historically. Concept / Approach: Red Hat's primary and longest-supported platform was the IBM-compatible x86 PC family. There were periods of official ports for architectures such as Alpha and SPARC in some releases. In contrast, classic Apple Macintosh (particularly pre-Intel PowerPC Macintosh) was not a primary supported target for Red Hat Linux; other distributions (like Yellow Dog Linux) focused on PowerPC Macintosh systems. Therefore, among these choices, 'Macintosh' best represents the architecture not supported as a main Red Hat platform. Step-by-Step Solution: Identify IBM-compatible (x86) as Red Hat's core platform.Note historical ports for Alpha/SPARC that existed in some releases.Observe that PowerPC Macintosh support was not a principal Red Hat focus.Select 'Macintosh' as the unsupported primary target among the options. Verification / Alternative check: Review old Red Hat release notes and installation manuals. You will commonly find x86 as primary, with occasional mentions of Alpha/SPARC editions in certain versions, and little to no official Red Hat Macintosh support compared to PowerPC-focused distributions. Why Other Options Are Wrong: IBM-compatible: The canonical Red Hat platform. Alpha: Had official ports in some eras. SPARC: Also saw Red Hat ports historically. None of the above: Incorrect because 'Macintosh' is the outlier here. Common Pitfalls: Conflating modern Fedora/derivatives (which may have broader community ports) with historical Red Hat Linux, or assuming that PowerPC Macintosh was a first-class Red Hat target. Final Answer: Macintosh

Question 6

Within the TCP/IP suite, which protocol provides remote terminal connection service (allowing users to log in to a remote host interactively)?

Accepted Answer

Introduction / Context: Remote administration and interactive sessions predate SSH. In the classic TCP/IP suite, a standardized protocol enabled users to open a terminal session on a remote machine. Recognizing the purpose of each protocol avoids misconfiguration and helps in understanding historical tools and their modern replacements. Given Data / Assumptions: We are discussing legacy, clear-text protocols in the original TCP/IP stack. Focus is on interactive remote terminal access. Options include protocols with distinct functions unrelated to terminal login. Concept / Approach: TELNET (TCP port 23) provides an interactive, text-based remote terminal connection. It negotiates terminal options and transmits keystrokes and screen output. Although insecure by modern standards (no encryption), it is the classic answer for remote terminal service. In contrast, FTP handles file transfer, UDP is a transport layer protocol (not an application protocol), and RARP maps MAC addresses to IPs in early boot scenarios; none of these create an interactive login shell like TELNET does. Step-by-Step Solution: Identify the need: interactive, bidirectional terminal session.Map to protocol: TELNET fits this use case.Eliminate distractors: FTP (file transfer), UDP (transport), RARP (address resolution).Select TELNET as the correct protocol. Verification / Alternative check: Modern practice uses SSH (Secure Shell) as a secure replacement for TELNET. Running 'telnet host 23' (if available) demonstrates the unsecured login prompt, reinforcing TELNET's role while highlighting its security drawbacks. Why Other Options Are Wrong: FTP: Transfers files; does not provide terminal login. UDP: A transport; not a remote terminal application protocol. RARP: Used for address resolution during booting diskless systems; not interactive login. None of the above: Incorrect because TELNET directly satisfies the requirement. Common Pitfalls: Equating TELNET with SSH in security properties (they are not equivalent) or believing FTP includes remote command execution by default—it does not provide an interactive shell. Final Answer: TELNET

Question 7

In free and open-source software history, the acronym FSF stands for which organization that champions user freedoms such as the right to run, study, share, and modify software?

Accepted Answer

Introduction / Context: The Free Software movement introduced a rights-based framing for software usage and development. The organization most closely associated with this movement has influenced licensing (for example, the GNU General Public License) and advocacy for users' control over their computing. Recognizing the correct expansion of FSF is a common foundational question in IT curricula. Given Data / Assumptions: FSF is a widely cited acronym in software freedom discussions. The question concerns the official name of the organization, not a technical component. Distractor options resemble plausible but incorrect expansions. Concept / Approach: FSF expands to Free Software Foundation, a nonprofit founded to support the development of free software (not merely zero-cost, but freedom-respecting) and to promote licenses that secure users' freedoms to run, study, share, and modify programs. The FSF sponsors projects such as GNU and maintains positions on software patents, DRM, and user rights. Step-by-Step Solution: Identify the domain: software freedom and licensing.Recall the canonical expansion: Free Software Foundation.Eliminate look-alike expansions that are not organizational names.Select the accurate organizational name. Verification / Alternative check: Review common references to the GNU Project, GPL licenses, and official statements; they cite the Free Software Foundation by its full name, never by the alternative phrases offered in distractors. Why Other Options Are Wrong: Free Software File: Not an organization; a mismatched phrase. File Server First / First Serve First: Irrelevant to the free software movement. None of the above: Incorrect because the exact, correct expansion is available among the options. Common Pitfalls: Confusing 'free' as in price with 'free' as in freedom; FSF emphasizes user freedoms irrespective of cost. Final Answer: Free Software Foundation

Question 8

In the context of DNS on Unix/Linux systems, which server daemon is provided with the BIND (Berkeley Internet Name Domain) package?

Accepted Answer

Introduction / Context: BIND (Berkeley Internet Name Domain) is the most widely used Domain Name System (DNS) software on the Internet. To understand DNS server configuration in Linux/Unix environments, it is important to know the name of the actual daemon process included with BIND. Given Data / Assumptions: The package in question is BIND. We need to identify the specific server daemon associated with it. Linux/Unix system service naming conventions apply. Concept / Approach: The BIND package provides the 'named' daemon (short for 'name daemon'). This service listens for DNS queries and responds based on configured zone files. It is typically managed by systemd or init scripts on Linux distributions and runs continuously to provide DNS resolution. Step-by-Step Solution: Check package: BIND includes the named binary.Start/stop service: systemctl start named or service named start.Confirm process: ps -ef | grep named.Verify DNS: dig example.com @localhost to test. Verification / Alternative check: Examine /etc/named.conf for configuration and run named -v to check version. Many Linux distros bundle named as part of the 'bind' package. Why Other Options Are Wrong: httpd: Apache web server, unrelated to DNS. shttp: secure HTTP daemon, not part of BIND. dns: generic label, not the actual daemon name. None of the above: incorrect since 'named' is correct. Common Pitfalls: Confusing the service name 'bind' (package) with 'named' (daemon). Assuming DNS resolution on Linux is handled by systemd-resolved; BIND remains widely used for authoritative and recursive servers. Final Answer: named.

Question 9

On Unix/Linux systems, which command is used to remove an empty directory from the filesystem?

Accepted Answer

Introduction / Context: Managing directories from the shell requires specific commands. Unlike removing files, removing directories safely ensures that filesystem structure is not corrupted. There is a specific command in Linux for deleting empty directories. Given Data / Assumptions: The directory is empty (contains no files or subdirectories). We are using a Unix/Linux shell with standard GNU coreutils. Concept / Approach: The rmdir command removes directories, but only if they are empty. For non-empty directories, rm -r is needed. Using the correct command prevents accidental recursive deletions. Step-by-Step Solution: Create test: mkdir testdirRemove: rmdir testdirError if not empty: 'Directory not empty'Use rm -r testdir for forced recursive deletion if needed. Verification / Alternative check: Check with ls before and after removal. rmdir will fail on directories with contents, which is expected behavior. Why Other Options Are Wrong: rdir: not a valid Linux command. remove: command does not exist in standard Unix. rd: DOS/Windows command, not Linux. None: incorrect because 'rmdir' is correct. Common Pitfalls: Confusing 'rmdir' with 'rm -r'; rmdir only works for empty directories. Using DOS-style 'rd' on Linux, which will not work. Final Answer: rmdir.

Question 10

In the OSI reference model, which layer defines the interface between the system and the end user, providing services such as file access, email, and virtual terminals?

Accepted Answer

Introduction / Context: The OSI (Open Systems Interconnection) model has seven layers, each with distinct functions. Identifying the correct layer that provides user-facing services is key to mapping protocols and troubleshooting networking issues. Given Data / Assumptions: We need the layer that defines the user interface for network services. Examples include file transfer, remote login, email, and directory services. Concept / Approach: The Application layer (Layer 7) is closest to the user. It provides the interface between applications and the underlying network services. Protocols like HTTP, SMTP, FTP, and Telnet operate at this layer. It does not include the graphical UI but defines the network service layer accessible by applications. Step-by-Step Solution: Identify goal: interface with the end user.Match OSI responsibilities: Application layer provides services like email, file transfer.Conclusion: correct layer is Application. Verification / Alternative check: Review OSI responsibilities: Layer 5 (Session) manages sessions; Layer 6 (Presentation) translates formats; Layer 7 (Application) interacts with user processes. Only Layer 7 fits the description. Why Other Options Are Wrong: Session: manages sessions and dialogues, not direct user interface. Data-link: handles framing and local delivery, not user interface. Network: routing and addressing; not for user-facing services. None: incorrect since Application is correct. Common Pitfalls: Assuming 'Application layer' means GUI programs—it refers to protocol layer providing services to software. Confusing Session and Application layers. Final Answer: Application.

Question 11

In free software history, the acronym GNU stands for which recursive phrase?

Accepted Answer

Introduction / Context: GNU is a foundational project in the free software movement, started by Richard Stallman in 1983. Understanding the meaning of its name helps contextualize its philosophy and importance in the history of Linux and open-source software. Given Data / Assumptions: The acronym in question is GNU. We are discussing the GNU project in computing, not unrelated terms. Concept / Approach: GNU is a recursive acronym for 'GNU's Not Unix.' It emphasizes that while GNU was designed to be Unix-compatible, it was developed independently and released as free software. The recursive naming style reflects hacker humor and traditions in computing culture. Step-by-Step Solution: Identify acronym: GNU.Expand recursively: GNU's Not Unix.Note philosophy: compatible with Unix but free/open source.Association: GNU components plus Linux kernel form GNU/Linux systems. Verification / Alternative check: Check GNU.org project pages, which confirm the recursive acronym. Verify that GNU utilities (gcc, bash, glibc, coreutils) are part of most Linux distros. Why Other Options Are Wrong: Greek Needed Unix, General Unix, General Noble Unix: fabricated expansions with no relation to computing history. None: incorrect because the correct phrase is listed. Common Pitfalls: Thinking GNU is just another Unix—GNU specifically emphasizes being independent and free. Overlooking that Linux distributions often combine GNU software with the Linux kernel. Final Answer: GNU's not Unix.

Question 12

In the vi editor, which command appends new text at the end of the current line?

Accepted Answer

Introduction / Context: Text editing in vi involves switching between normal and insert modes. Knowing the difference between lowercase and uppercase commands allows faster editing. Appending specifically at the end of a line is a common task. Given Data / Assumptions: You are using vi/Vim in normal mode. You want to add text at the end of the current line without manually moving with arrow keys. Concept / Approach: The uppercase command A moves the cursor to the end of the line and enters insert mode, ready for appending. This differs from lowercase a, which appends immediately after the cursor only. Step-by-Step Solution: Open a file in vi.In normal mode, press A.Cursor jumps to end of line, then insert mode starts.Type additional text and press ESC to return to normal mode. Verification / Alternative check: Compare A with lowercase a. Use A to quickly append to a line regardless of cursor position. Why Other Options Are Wrong: I: inserts at beginning of line. i: inserts before cursor. a: appends after cursor, not end of line. None: incorrect because 'A' is correct. Common Pitfalls: Confusing lowercase and uppercase commands in vi—they have different behaviors. Assuming a will always take you to end of line—it does not. Final Answer: A.

Question 13

In the vi editor, which command searches for a pattern in the forward direction from the current cursor position?

Accepted Answer

Introduction / Context: Searching text efficiently is central to navigating in vi/Vim. Different search commands look forward or backward, and knowing the right one for forward search saves significant time. Given Data / Assumptions: You are in normal mode in vi/Vim. You want to search forward in the file from the cursor location. Concept / Approach: The / command starts a forward search. After typing /pattern, pressing Enter will move the cursor to the next occurrence of 'pattern' after the cursor. Typing n repeats the search forward; N repeats it in the opposite direction. Step-by-Step Solution: Enter normal mode.Type /pattern and press Enter.The cursor jumps to the next match in forward direction.Use n to repeat search forward, N to reverse. Verification / Alternative check: Compare with ?pattern, which searches backward. Try on a sample file with repeated words to confirm direction. Why Other Options Are Wrong: ??: invalid, not a vi command. //: repeats last search, does not initiate. ?: backward search. None: incorrect because / is correct. Common Pitfalls: Confusing / with ? for direction. Forgetting to press Enter after typing the pattern. Final Answer: /.

Question 14

On Linux systems, which command is used to create a new file system on a partition or block device before it can be mounted?

Accepted Answer

Introduction / Context: Before a partition or block device can be used for storing files, it must be formatted with a file system. Linux provides a specific command for this purpose, which abstracts details of different file system types. Given Data / Assumptions: We have a new or unformatted partition or block device. We want to create a usable file system on it. Linux standard utilities are installed. Concept / Approach: The mkfs command ('make file system') initializes a partition with a chosen file system (ext4, xfs, vfat, etc.). Variants like mkfs.ext4 or mkfs.xfs provide specific implementations. Step-by-Step Solution: Identify device: lsblk or fdisk -l.Run: mkfs.ext4 /dev/sdb1 (example).Wait for formatting to complete.Mount the filesystem: sudo mount /dev/sdb1 /mnt. Verification / Alternative check: Check with file -s /dev/sdb1 or blkid. Mount and verify with df -h. Why Other Options Are Wrong: fdisk: partitions disks, does not format. fsck: checks and repairs file systems. mount: attaches a filesystem to a directory tree, does not create one. None: incorrect since mkfs is correct. Common Pitfalls: Confusing partitioning with formatting. Accidentally formatting the wrong device (always double-check identifiers). Final Answer: mkfs.

Question 15

In BSD printing systems, which command removes one or more jobs from the print queue?

Accepted Answer

Introduction / Context: Traditional Unix printing follows the BSD model, where different commands handle job submission, monitoring, and removal. Knowing which tool removes jobs from the queue is essential for administrators and users managing print workloads. Given Data / Assumptions: BSD printing commands are available (lpr, lpq, lprm, lpc). User has jobs in the print queue. Concept / Approach: The lprm command removes print jobs. By default, lprm with no arguments deletes the current user's jobs. Specific job IDs can also be provided. Administrators can remove jobs submitted by other users if permissions allow. Step-by-Step Solution: Submit job: lpr file.txtList queue: lpqRemove: lprm jobIDVerify: lpq shows job is gone Verification / Alternative check: Cross-check with CUPS logs (/var/log/cups/) and web UI if CUPS provides BSD-compatible lpr/lprm interfaces. Why Other Options Are Wrong: lpq: displays queue; does not remove. lpr: submits jobs; opposite of removal. lpc: printer control, not job deletion. None: incorrect since lprm is correct. Common Pitfalls: Forgetting job IDs when multiple jobs exist; lpq helps identify them. Confusing lprm with lpr (submission). Final Answer: lprm.

Question 16

In computer networking, which service translates human-readable domain names (for example, www.example.com ) into numerical IP addresses?

Accepted Answer

Introduction / Context: The Internet relies on a service that converts domain names into IP addresses so that clients can connect to servers without memorizing numeric values. This translation is fundamental for web browsing, email delivery, and most networked applications. Given Data / Assumptions: The goal is mapping names like www.google.com to IPv4/IPv6 addresses. We are comparing DNS to other unrelated services. Concept / Approach: The Domain Name System (DNS) provides hierarchical, distributed name resolution. A resolver queries recursive or authoritative servers, receives an IP address, and allows applications to establish network connections transparently to the user. Step-by-Step Solution: Type: dig www.example.com or nslookup www.example.com DNS server returns A (IPv4) or AAAA (IPv6) records.Application connects using IP received.If DNS fails, users must manually use IP addresses. Verification / Alternative check: Use ping www.example.com and observe it resolves to IP. Check system resolvers in /etc/resolv.conf or with systemd-resolve --status. Why Other Options Are Wrong: NFS: Network File System, unrelated to name resolution. SMB: Server Message Block, file/printer sharing protocol. NIS: Network Information Service, provides directory info but not DNS. None: incorrect because DNS is correct. Common Pitfalls: Confusing DNS with DHCP (which provides IP configuration, not name resolution). Assuming browser autocomplete replaces DNS—it still relies on DNS queries. Final Answer: DNS.

Question 17

In the vi editor, which command replaces text continuously from the current cursor position to the right, until you exit replace mode?

Accepted Answer

Introduction / Context: Vi provides both single-character replacement and continuous replacement modes. Knowing the difference is important for efficient editing when making larger inline changes without deleting whole words or lines. Given Data / Assumptions: User is editing text in vi normal mode. The goal is to overwrite multiple characters continuously. We must distinguish between lowercase r and uppercase R. Concept / Approach: The uppercase R enters replace mode, where every keystroke overwrites existing characters until you press ESC. Lowercase r replaces only one character. This makes R the correct choice for replacing text from the cursor onward. Step-by-Step Solution: Open file in vi.Navigate to text to overwrite.Press R (uppercase).Type replacement text; existing characters are overwritten.Press ESC to return to normal mode. Verification / Alternative check: Compare with lowercase r: rX replaces one character with X only. With R, typing 'HELLO' overwrites five existing characters until stopped. Why Other Options Are Wrong: S: changes entire line and enters insert mode. s: substitutes one character and enters insert mode for further input. r: replaces only a single character. None: incorrect because R is correct. Common Pitfalls: Confusing R with r; lowercase affects one character only. Forgetting to press ESC to exit replace mode. Final Answer: R.

Question 18

In Unix/Linux system administration, which command is used to display the characteristics and current status of running processes (for example, PID, TTY, CPU time, and the command)?

Accepted Answer

Introduction / Context: Being able to view process characteristics is essential for Unix/Linux troubleshooting and performance tuning. Administrators and developers rely on a standard tool to see a snapshot of running processes, including process IDs, controlling terminals, resource usage, parent relationships, and the command that launched each process. Given Data / Assumptions: You are using a Unix-like shell such as bash or zsh. You wish to inspect live process information like PID, TTY, CPU time, and command. No third-party utilities are assumed; only core system tools. Concept / Approach: The command 'ps' (process status) prints process attributes in various formats. Common invocations include 'ps aux' (BSD style) to list all processes system-wide and 'ps -ef' (SysV style) for a full-format listing. Options like '-o' allow custom column selection, while filters such as '-u user' or a specific PID restrict the output to what you need. Step-by-Step Solution: List your terminal's processes: psShow all processes: ps auxSysV-style full listing: ps -efCustom columns (PID and command): ps -eo pid,cmdFilter by user: ps -u username Verification / Alternative check: Cross-check PIDs reported by 'ps' with corresponding entries under '/proc/' on Linux, or use dynamic viewers like 'top'/'htop' to confirm that the same processes are present. Exit statuses and process hierarchies should align across tools. Why Other Options Are Wrong: pid: This is a process identifier concept, not a listing command. du: Reports disk usage; unrelated to process inspection. au: Not a standard command for process display. None of the above: Incorrect because 'ps' is precisely the required tool. Common Pitfalls: Mixing BSD and SysV option styles (some flags differ), assuming 'ps' auto-updates (it does not; it is a snapshot), or forgetting to elevate privileges when listing processes owned by other users and expecting complete results. Final Answer: ps

Question 19

In the vi (or Vim) text editor, which symbol is used to backspace over typing errors while entering text?

Accepted Answer

Introduction / Context: While editing in vi/Vim, you often need to correct mistakes quickly as you type. The question asks specifically for a symbol that backs up over typing errors. Understanding vi's Insert-mode editing keys prevents needless mode switches and speeds up everyday text manipulation. Given Data / Assumptions: You are in Insert mode (press Esc to leave, i to enter). You want to erase characters you just typed. Options presented are printable symbols (for example, '!', '$'). Concept / Approach: In vi/Vim, the normal way to correct typing errors in Insert mode is to press the Backspace key, which often generates the control character ^H. Some terminal configurations may also allow Control-H to act as backspace. These are control keys, not printable symbols. Therefore none of the listed punctuation characters perform the backspace function in vi's Insert mode by default. Step-by-Step Solution: Enter Insert mode with i.Type a few characters, then press Backspace to remove mistakes.If Backspace does not work, check ':set backspace?' and consider 'set backspace=indent,eol,start' in your vimrc.Use Esc to return to Normal mode; Normal-mode deletion uses commands like x and X. Verification / Alternative check: Run 'stty -a' in the terminal to confirm which control character is mapped as erase (commonly ^H or ^?). In Vim, ':help backspace' documents behavior and configuration that ensures Backspace works as expected in Insert mode. Why Other Options Are Wrong: '!': Shell history expansion in some shells; not a vi backspace. '$': End-of-line motion in many contexts, not deletion. '#': Not a backspace key in vi. '@': Macro register invocation in Normal mode; not a backspace. Common Pitfalls: Confusing Normal-mode commands with Insert-mode editing, or expecting printable symbols to perform control functions without custom mappings. Also, terminal misconfiguration can disable Backspace unless 'backspace' option is set in Vim. Final Answer: None of the above

Question 20

On Unix/Linux, which command is used to sort the lines of a file in ascending (alphabetical/lexicographic) order?

Accepted Answer

Introduction / Context: Sorting text is a common step in log analysis, report preparation, and data cleaning. The standard 'sort' utility orders lines lexicographically by default and can be tuned for numeric sorts, locale specifics, and key-based ordering, making it a versatile tool for shell pipelines and scripts. Given Data / Assumptions: You have a plain-text file containing multiple lines. You want the default ascending ordering. No special collation or key selection is required. Concept / Approach: Running 'sort filename' outputs lines in ascending order according to the system's locale. You can adjust behavior with options such as '-n' for numeric sort, '-k' to select sort keys, and '-r' for reverse order. Combining these options yields powerful one-liners for complex sorting tasks. Step-by-Step Solution: Alphabetical sort: sort input.txt > output.txtReverse order: sort -r input.txtNumeric sort on column 2: sort -k2,2n file.csvStable sort (GNU): sort -s -k1,1 file Verification / Alternative check: Compare the output of 'sort' with an editor's sorted view, or use 'uniq' afterwards to collapse duplicates if de-duplication is also desired. For numeric data, verify that '-n' is used; otherwise 10 may appear before 2 due to string comparison rules. Why Other Options Are Wrong: sort - r: Represents reverse sorting (and contains a spacing error); it is not the default ascending order. sh: Invokes the shell, not a sorting utility. st: Not a standard Unix command. None of the above: Incorrect because 'sort' is correct. Common Pitfalls: Forgetting '-n' for numeric fields, ignoring locale effects on ordering, or sorting the wrong column when working with delimited data without specifying '-k' and '-t' properly. Final Answer: sort

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