Section 13

What command lists the contents of a directory in Linux? (Windows equivalent: dir)

ls — lists file system objects; use ls -la to show all files including hidden (dot) files with permissions, owner, group, size, and date

What command prints the current/working directory in Linux?

pwd (print working directory)

What command changes directories in Linux?

cd — use cd .. to go up one directory, cd . for current directory

In Linux, what command moves OR renames a file?

mv (move) — format: mv source destination. Moving copies the file then deletes the original

What command copies a file in Linux?

cp (copy) — format: cp source destination. Leaves the original intact

What command deletes/removes a file in Linux? How do you remove a non-empty directory?

rm (remove). Use rm -rf (recursive + force) to delete a directory and its contents

What command displays free disk space per file system in Linux?

df (disk free) — shows file system, total size, used, available, % used, and mount point

What command estimates disk usage of files/directories in Linux?

du (disk usage) — shows size of a directory, its contents, and underlying directories

What Linux command checks and repairs a file system? (Windows equivalent: chkdsk)

fsck (file system check) — unmount the file system first; often runs automatically after an unclean shutdown

What command attaches a file system to a directory in Linux?

mount — temporary; lost on reboot. For persistent mounts, edit /etc/fstab

Name the easy-to-use Linux command-line text editors.

nano and pico — beginner-friendly with on-screen command hints (e.g., Ctrl+O to save, Ctrl+X to exit)

What is vi and what makes it different from nano?

vi — an older MODAL text editor (insert mode, command/normal mode). Harder to use; no on-screen menu. vim = "vi improved" (adds spell check, autocomplete, plugins)

What does the cat command do in Linux?

Concatenate — creates, views, or combines files. Use > to overwrite a file, >> to append to a file

What command searches the file system for a file by name, date, owner, or permissions?

find — e.g., find directory -name file2.txt

What command searches for a string/regular expression INSIDE a file?

grep (Global Regular Expression Print) — useful for searching log files

find vs grep — which searches for files and which searches inside files?

find = searches for files (by name/attributes). grep = searches for content within files

What command switches to another user in Linux?

su (substitute user) — requires that user's password

What command runs a single command as the root user? (Windows equivalent: Run as administrator)

sudo (superuser do) — the account must be on the sudoers list

What are the commands to add, modify, and delete a USER in Linux?

useradd (create), usermod (modify), userdel (delete)

What command changes or resets a user's password in Linux?

passwd

What are the commands to add, modify, and delete a GROUP in Linux?

groupadd (create), groupmod (modify), groupdel (delete)

What command changes file/directory permissions in Linux?

chmod (change mode) — uses symbolic or octal notation

In chmod octal notation, what are the values for read, write, and execute?

read (r) = 4, write (w) = 2, execute (x) = 1. Add them together per group. Example: rwx = 7, rw- = 6

What does chmod 664 mean for the three permission groups?

Owner = rw- (6), Group = rw- (6), Everyone = r-- (4). Order is always Owner, Group, Everyone

What command changes the OWNER of a file/directory in Linux?

chown (change ownership)

What command changes the GROUP ownership of a file in Linux?

chgrp (change group)

How do you read a Linux permission string like drwxr-xr--?

First char = type (d = directory, - = file). Then 3 sets of 3: Owner, Group, Everyone — each as read/write/execute

Which package manager is used on Debian-based distros (e.g., Ubuntu)?

apt / apt-get (Advanced Packaging Tool) — uses .deb packages

Which package managers are used on Red Hat-based distros (Red Hat, CentOS, Fedora)?

rpm (oldest, low-level), yum (easier), and dnf (newest, updates yum) — use .rpm packages

What command displays a list of currently running processes in Linux?

ps (process status) — use ps -e to see all processes across all users

What Linux command shows real-time CPU and memory usage by process? (like Task Manager)

top

What command configures network interfaces and shows IP info in Linux? (replaced the older ifconfig)

ip — e.g., ip addr (shows IP), ip link (interface status)

How does the ping command differ in Linux vs Windows?

Linux pings INDEFINITELY until stopped (Ctrl+C); Windows sends 4 by default. Use ping -c 4 to limit count in Linux

What is the Linux spelling of the route-tracing command?

traceroute (fully spelled out; Windows uses tracert)

What command queries DNS servers for domain name info in Linux? (like nslookup)

dig — e.g., dig diontraining.com

What command transfers data to/from servers and supports HTTP, HTTPS, FTP, etc.?

curl (client URL) — useful for testing web services/APIs

How do you get help on a Linux command?

--help (after the command name) for basic usage, OR man (manual pages) for detailed reference

What are the three key components of the Linux OS (boot to runtime)?

Bootloader (loads kernel into memory), Kernel (core — manages hardware/software, processes, memory), systemd / system daemon (initializes and manages services at runtime)

Name two common Linux bootloaders.

GRUB (Grand Unified Bootloader — more common) and LILO (Linux Loader)

What does the Linux /etc/passwd file store?

User account info (username, UID, GID, home directory). Used for authentication. Passwords NOT stored here anymore

What does the Linux /etc/shadow file store?

Encrypted passwords + security info (last change date, expiration). Readable only by root

What does the /etc/hosts file do in Linux?

Local mapping of IP addresses to hostnames (resolves names without DNS)

What does the /etc/fstab file do in Linux?

Defines how storage devices/partitions are mounted — read at boot for automatic, persistent mounting

What does the /etc/resolv.conf file do in Linux?

Configures the DNS client — specifies which name servers to query for domain name resolution

What is Samba in Linux?

A cross-platform file-sharing tool that supports the SMB (Server Message Block) protocol, used to share files/printers with Windows systems

What service and editor are used to schedule automated tasks (e.g., backups) in Linux?

cron service; edit jobs with crontab -e (crontab editor)

What are the key Linux best practices for the exam?

Updates/patches (apt-get or yum/dnf/rpm), antivirus (e.g., ClamAV) + firewall/IDS/IPS, backups (cron + tools like tar/gzip), and Samba for Windows integration