CentOS Linux Administration

Master absolute and relative paths, learn your present working directory with pwd, and identify file types: regular files, directories, executables, symbolic links, and device files using the file command.

Learn to use the find command to locate files and directories across a directory tree using criteria like name, permissions, size, and type, and to perform actions on matches.

Learn to use the find command to locate files and directories. Use -exec for commands like chmod 644, delete files, and find empty or hidden files and directories by type.

Install the locate tool on Red Hat Linux, update its database regularly, and use locate for fast, case-insensitive file search while requiring root privileges.

Learn how to manage linux file permissions and access rights, using ls -l to view owner, group, and others, and chmod to add or remove read, write, and execute rights.

Create a directory in your home folder and a file, then view and adjust permissions with chmod, including recursive changes, and manage ownership and group assignments.

Learn vim basics with two modes, insert and normal, switch via escape or i, navigate with h j k l and shortcuts w b e, and search and edit efficiently.

Learn Vim basics for CentOS Linux administration: switch between insert and command modes, navigate with h j k l, edit text, and save with w and quit with q.

Learn how to access Vim help from the command line, browse topics, begin typing to filter results, and exit back to your session.

Practice creating and editing a new file in vim by naming it text one, inserting text, exiting insert mode with escape, and saving with wq.

Open Vim at a specific line or by search pattern, use read-only mode to protect edits, and recover changes after a crash using Vim's capabilities.

Learn to open multiple files and split windows in vim from the command line, using horizontal and vertical splits, buffers, and status line control to navigate and edit efficiently.

Enable vim's mouse option to work with two files when the mouse is disabled by default, and use control-w to quickly switch between windows.

Install vim on ubuntu, macOS, or Windows, launch vim, enter insert mode, and navigate text with h, j, k, l, w, B, 0, and $ using numeric multipliers.

Learn basic Vim editing for CentOS Linux administration, including movement, search highlighting, copying and pasting lines, deleting to end of file, and inserting text with append and O commands.

Practice vim navigation with hands-on exercises, learning to move between paragraphs using curly braces and jump to the start, middle, and end of the window, line, and file.

Learn advanced vim navigation and editing, including searching for Python occurrences with n and N, deleting words and lines, deleting to end of line, and using undo, redo, and save.

Learn Vim basics and advanced text editing, from creating and opening files to deleting, copying, pasting, undoing, and redoing, with visual mode, multi-line edits, and customization.

Practice text editing in vim by creating and editing a file, entering insert mode, deleting, undoing, changing words, moving, appending, searching, yanking, pasting, and commenting with a visual block.

Master vim editing techniques for CentOS administration by practicing block moves, text deletion, and reordering sections, using search, visual selection, and the global command to insert notes.

Explore how bash initializes per user, uses startup and initialization files, and leverages the bash history to recall and edit past commands with history and exclamation marks.

Learn to use the cat command to read files and standard input, redirect output to new files with the > operator, and concatenate multiple files into one.

Connect the output of the who command directly to sort or wc using a pipe, eliminating temporary files and enabling quick counts of logged on users.

Learn to manage linux processes and jobs, foreground and background execution, using & and the jobs, fg, and the bg commands, suspend with ctrl-z, and kill with pid or %job.

Master essential special characters and keystrokes used in the CentOS shell, including exclamation mark, slashes, quotes, brackets, underscore, asterisk, and navigation shortcuts like ctrl-a and ctrl-e.

Chain commands in CentOS Linux administration using backgrounding with ampersand, semicolon separators, and conditional operators &&, ||, and ! to control execution with file and cat examples.

Learn to view and print the current shell aliases, set per-session aliases for commands like ls, persist them in ~/.bashrc, and remove all aliases with unalias -a.

Explore using the watch command to monitor command output and file changes in real time, adjust the refresh interval, highlight differences with -d, and pair with tail for live logs.

Explore how Red Hat Enterprise Linux manages rpm packages, including dependency resolution, package naming conventions, metadata storage, and subscription management via the customer portal.

Install and manage packages on CentOS using rpm commands, handle dependencies, upgrade, freshen, and overwrite or remove packages, and verify integrity with md5 and gpg keys.

View GPG keys with rpm, verify package attributes using rpm -V, and interpret the codes that signal changes to owner, group, permissions, size, and digest.

Explore Yume, the Yellow Dog Updater Modified, a front end to RPM for package management via software repositories, configured via yume.conf with cache, log, gpg, plugins, and obsoletes.

Explore yum's common subcommands, manage repositories, and build a local yum repository from installation media; install packages, search, update, and review history with wrapper tools.

Master the yum package manager in CentOS Linux administration by installing, updating, searching, and removing packages and package groups, using local and remote repositories, and tracking transaction history.

Master the ip command to view and assign addresses, inspect link and address details with ip link show and ip address show, and explore route management with ip route.

Master nmcli to manage the network manager daemon, devices, and connections in CentOS, creating, activating, and modifying DHCP and static configurations, viewing status, and applying DNS and IP settings.

Validate network configuration by listing interfaces with ip link and ip addr show, identifying MAC and IP addresses. Use tracepath or traceroute and ss to verify routing, connectivity, and sockets.

Configure a static IPv4 lab connection on eth2 with 172.25.250.11/24 and 10.0.1.1/24, gateway 172.25.250.254, and DNS 172.25.250.254. Set auto start, update hosts file, reboot, and verify.

Explore how user accounts define security boundaries with root, system, and regular users; use id, ps, and ls to reveal ownership and process information from /etc/passwd.

Practice gaining superuser access with sudo, switching to root, and inspecting environment variables like home and path; create a test user with sudo privileges.

Create and manage user accounts in CentOS Linux administration by adding operator two, operator three, and operator four; modify details with usermod and set passwords, then delete operator four.

Create and verify local groups operators (GID 30,000) and admin, add users with usermod -aG, confirm with id and /etc/group, and grant admin rights via /etc/sudoers.d/admin using sudo.

Master local users and groups management by creating the consultants group (gid 40000), granting sudo rights, adding consultant1–3, and enforcing 90-day expiry, 15-day policy for consultant2, and first-login password changes.

Explore how Linux file permissions govern access to files by owner, group, and others, with read, write, and execute rights, where the most specific permissions apply.

Master file and directory permissions with chmod by using symbolic and numeric methods to set read, write, and execute rights for user, group, and others, including recursive changes.

Manage file and directory ownership on CentOS by using chown with owner:group syntax, apply -R for recursive changes, and use chgrp as an alternative for group ownership.

Discover how to control default permissions with umask and set special permissions such as setuid, setgid, and sticky to manage group ownership and file access on CentOS Linux.

Learn to control file access in a CentOS linux administration lab by creating a shared directory, setting tag docs group ownership, applying setgid, and enforcing a restrictive umask.

Learn to monitor and control Linux processes on a Red Hat Enterprise Linux eight system, using ps and top to view status, resource use, ownership, load average, and process states.

Analyze Linux load average and identify processes causing high resource use on a server, considering CPU, disk I/O, and network I/O, with tools like uptime and top.

Learn to access remote command lines securely using ssh with OpenSSH on CentOS Linux. Configure key-based authentication, restrict root and password logins, and manage host key verification and known_hosts.

Configure OpenSSH to disable direct root logins and password authentication, enable key-based authentication, and reload sshd to apply changes.

Describe how the system log architecture records events with system journal and syslog, configure journaling and time synchronization with NTP, and navigate /var/log files like messages, secure, cron, and boot.log.

Explore how syslog uses facilities, priorities, and severities, and configure rsyslog rules to route messages to files. Learn to monitor logs with tail and test logging with logger.

Configure the system journal to persist across reboots by setting the storage parameter to persistent, volatile, or auto in the systemd journald configuration, and verify with journalctl and reboot checks.

Learn to archive and compress files with tar, creating, listing, and extracting archives, using gzip, bzip2, or xz compression. Transfer securely and synchronize local files with remote servers via ssh.

Schedule deferred tasks on CentOS using the at daemon and the add command with flexible timespecs. View, inspect, and manage these jobs via ad queue and add commands.

Learn to interpret and set access control lists (ACLs) on files and directories with getfacl and setfacl, including default ACLs, named users, named groups, mask, and precedence.

Extend the logical volume and volume group by adding a new pv, then resize the logical volume and the mounted zfs filesystem, verifying with df and ls commands.

Resize server1 lv1 to 768 MiB and create server1-lv2 128 MiB with a zfs file system mounted persistently at /storage/data2, illustrating LVM concepts like PV, VG, and LV.

Create and manage a Stratis pool, add data devices, and deploy a thin provisioned Stratis file system. Verify dynamic growth and access data from a snapshot via mount.

Learn to configure Stratis storage pools on CentOS, create thinly provisioned file systems, snapshot and mount volumes, and explore deduplication and compression with a virtual data optimizer.

Learn to mount and unmount NFS shares on CentOS, create mount points, use mount and fstab for persistent access, and configure NFS conf for NFS version 4.

learn to view and set the default boot target, switch to multi-user, and boot into rescue mode on CentOS Linux using systemctl and bootloader menu techniques.

Learn to control the boot process in CentOS: reset root password, troubleshoot boot failures, fix fstab and SELinux relabel, and set the default target to graphical.

Master foundational IPv4 networking concepts—tcp/ip four-layer model, ip addressing, subnet masks and cidr, routing tables, and name resolution—through hands-on labs using nmcli and static configurations.

Create a private key with OpenSSL on Red Hat Linux, using RSA 2048, protect with a passphrase, and generate a self-signed X.509 certificate for a server host.

Create and manage a certificate authority with self-signed roots using OpenSSL, generating a 2048-bit private key, a root certificate, and preparing to sign server certificates.

Create a self-signed CA certificate and a server certificate using OpenSSL, generate private keys and CSRs, sign requests, and prepare server and CA directories for testing TLS.

Learn Linux root access security through hands-on practice, check root status with su and sudo, and explore modular sudoers handling per-user and per-role rules.

Configure granular sudoers policies to enforce least privilege, shaping sudoers structure, environment controls, and role based access for users and groups, with no password policies and secure path enforcement.

Create a restrictive sudo configuration for the service admin user in sudoers.d to allow passwordless systemctl and journalctl across all servers, while requiring passwords for apt update or dnf upgrade.

Define role-based access control groups for web admins, db admins, and backup admins. Configure sudoers for group members with no-password access and a 60-minute password grace for backups.

Master sudoers file permissions and role-based access validation on CentOS Linux by ensuring root ownership, 0440 permissions, and testing web, db, and backup admin access, including nginx and mariadb actions.

Explore environment security in sudoers to prevent privilege escalation by enforcing a clean environment, secure_path, and safe env_keep settings, and deleting dangerous variables like ld_preload.

Demonstrates testing environment variables to reveal privilege escalation risks via ld preload, and shows how sudo env handling and secure_path mitigations through sudoers configuration protect against leakage.

Analyze effective sudo policies for users and groups in CentOS, inspect allowed commands with sudo -l and -U, and troubleshoot policy mismatches via error redirection.

Explore sudoers best practices and set up a modular configuration repository that enforces least privilege, with example role configurations published on GitHub.

Learn to use udevadm to query the udev database, view device attributes, and monitor real time udev events for troubleshooting hardware and writing rules.

Install the btrfs module and utilities on Red Hat Enterprise Linux, troubleshoot package availability, and manage repositories, subscriptions, and snapd for Snap package manager, using dnf, CodeReady Builder, and EPEL.

Use dmesg to monitor kernel messages and troubleshoot hardware, with readable timestamps and colorized output, and filter for errors and warnings in real time.

Explore the lspci command to view PCI devices, IRQ settings, PCI bus speed, and vendor identification, while noting it omits system battery type and Ethernet MAC address.

Explain how systemd treats manually mounted file systems not in fstab and how systemctl mount sync can create a mount unit from an existing mount, with a usb example.

Master using the man command to access section 1 manuals for user commands, navigate docs efficiently with specific sections, and read command and configuration file information in CentOS Linux administration.

Explore the ln command, create hard links that share the same inode, and differentiate symbolic (soft) links with practical examples and inode checks.

Explore system v init configuration by examining symbolic links in rc two dot d, and learn how s and k scripts start or stop apache2 at runlevels one and two.

Identify which package owns a given file on Debian systems using dpkg -S, with examples like /etc/debian_version and /bin/bash.

Explore archive manipulation with gzip and tar. Gunzip texts.tgz containing a.txt and b.txt leaves texts.tar, illustrating how gzip, gunzip, and tar work together.

Explore the bios boot sequence, including configurable boot steps and how the bios initiates boot after power on, with the bootloader loading the linux kernel.

Learn how to remove packages with dpkg purge, which deletes both the package and its configuration files, and compare it to dpkg remove through a hands-on htop example.

Explore linux process management with nice levels and the nice command to start a process with modified priority. Note that default nice value is zero, and values range from -20.

Demonstrates how to print the current working directory in bash using the PWD command or the echo ${PWD} variable, highlighting case sensitivity and script usage.

Extract usernames and their login shells from /etc/passwd using cut -d: -f 1,7, then format with column -t -s : for readability.

Discover that on system v init-based systems the init process has pid 1, consistently across reboots and run levels, and is the first process responsible for system initialization.

Prevent faulty kernel modules from loading at boot by blacklisting the module in /etc/modprobe.d/blacklist.conf; use modprobe -r for temporary unloads, then reboot to verify.

Learn how to use the Zypper package manager for pattern-based installation, including installing all packages ending in foo with the asterisk wildcard, and performing a dry run.

Explains how Ctrl+Z sends the stop signal (Sigstop) to foreground processes, how to suspend and resume with bg/fg, and how Sigint (Ctrl+C) differs from Sigstop in Unix-like systems.

Learn how to use the tee command for command output redirection to display results on screen while saving them to a file, enabling real-time logging, debugging, and monitoring.

Use the find command to locate files owned by root in /tmp and subdirectories, print results with -print or rely on implicit, and search by -user root or -uid root.

Learn how to use the tune to fs command to set the file system check interval to 200 days on /dev/sda1 for ext2/3/4, balancing boot time and system integrity.

Convert windows line endings to linux by using tr -d '\r' to remove carriage returns from a text file, creating a linux-formatted output such as new list.txt.

Pressing control plus C sends SIGINT, the interrupt signal, allowing a process to catch it and terminate gracefully instead of SIGKILL, a forced termination.

Install grub boot files into the active file systems and the boot loader on the first disk with grub install /dev/sda, using sudo for privileges.

Run rpm --query --all to list all installed packages on an rpm-based system, such as CentOS nine, and browse results with a pager like less.

Learn how to install grub2 into the master boot record on the third hard disk using grub install dev sdc with sudo, noting the target device may vary.

Learn how appending an ampersand to a command runs it in the background of the current shell, freeing the terminal for other tasks, with practical examples.

Repair ZFS file system inconsistencies after power outages using zfs repair on an unmounted system, avoiding force mounts or special mount options.

Learn why hard links are limited to one file system and cannot point to files on a different system. The lecture demonstrates creating a hard link and confirms identical inodes.

Identify that man pages are stored in the usr share man directory per the filesystem hierarchy standard, ensuring consistent access by the man command across CentOS Linux systems.

Learn how to display inode numbers for files on Linux using ls -i and the stat command, and understand how inode metadata helps identify file information.

View the contents of a gzip compressed tar archive using tar z tf archive.tgz to peek inside without extracting.

Explore how the split command divides a large file into smaller segments, using a specified line count, with a practical demonstration on generating split_log files in CentOS Linux administration.

Configure yum repositories on Red Hat based Linux systems by distributing repository definitions across multiple files in etc/ume wrappers.d, using base, search, and releasever variables for dynamic URLs.

During boot with system v init, the kernel starts /sbin/init (PID 1), the parent of all processes. Learn how to inspect the init process and its command line.

Search file contents with regular expressions using grep, a tool for Linux administration. Grep represents global regular expression print and supports log analysis, code review, and troubleshooting.

Learn how hard links in backup software improve storage efficiency and speed by reusing inodes to avoid duplicating unchanged files, while noting cross-file-system limitations.

Apply the find command's maxdepth option to limit searches to a specific number of subdirectory levels, preventing deep traversal in nested directories.

Compare Linux containers with traditional virtual machines by examining kernel controlled process isolation, resource management, hypervisor roles, and how containers on the same host share the host kernel.

Learn how to paste deleted content below the current line in vi using the lowercase p command, with a practical walkthrough of delete and put operations in CentOS Linux administration.

Learn to execute shell scripts in the current shell without spawning a subshell using the source command or the dot operator, so environment changes persist.

Explore how a braille display provides a tactile interface, translating digital content into small raised dots for visually impaired users.

Identify that the /etc/passwd file stores a user's primary group and other essential details in colon-delimited fields, and practice locating your own account and its primary group.

Identify valid IPv6 addresses by recognizing eight groups of four hexadecimal digits separated by colons, using 0–9 and A–F, with a single double colon to compress zeros.

Learn how the dot forward file routes incoming mail to one or more recipients, with immediate effect, and understand user ownership and permissions in Linux mail management.

Explore DNS resolution on CentOS by configuring resolv.conf with keywords such as search and nameserver, learn about default domain appending, and safely edit the file.

Learn how to use the dig command for DNS debugging, which shows the name server response and query details, including query time, server used, and mx records when requested.

Locate and edit the SSH client configuration file at /etc/ssh/ssh_config and view host settings. Create a user config at ~/.ssh/config with host and user, then connect with ssh.

Use the journalctl since and until parameters to define a precise time window for log queries, viewing entries from a start time onward up to an end time.

Discover the two key network manager states, portal and full connectivity, and learn to observe them with the network manager cli on Linux.

Use lpstat and lpqueue to display and monitor print queue jobs in a Linux environment. Practice checking the current queue and understanding results when no printer is connected.

Use the chage command to modify password expiry information, including minimum and maximum days between changes, last change date, account expiration, and warning period.

Identify the Spice protocol as the virtual machine video output protocol designed for VM graphics output, delivering low latency and high-quality display.

Explain which files are read directly by a bash login shell and why .bashrc is not among them, while outlining the startup-file order including /etc/profile, ~/.bash_profile, ~/.bash_login, and ~/.profile.

Learn how nmcli device wifi connect creates and activates a new wifi connection, naming it and handling errors, with practical steps to list networks and disconnect when needed.

Configure global shell variables by editing the /etc/profile file to apply variables system-wide at login. The lecture shows exporting a variable and validating it with echo.

Learn how sudo configuration controls user permissions, including no password and password directives that govern commands like kill, id, and fdisk, with root password required for some actions.

Spice enables remote application access, local USB device integration, and downloading and locally installing applications from a remote machine; it does not replace X.Org and cannot upload or run binaries.

Discover how the systemd timer unit schedules tasks through the timer section, using on boot and on calendar directives to trigger its associated service, as shown with hello.service and hello.timer.

Explore bash scripting with a while read loop that processes echo 1-6 through a pipe, assigns to a, b, c, and echoes in reverse to produce 345621.

Use valid shell script syntax in the dot profile file in a user's home directory, since it is sourced on login; it need not be executable or have a shebang.

Identify how the /etc/group file stores group names and the comma-separated member lists, while noting that it omits home directories, default ACLs, and group descriptions.

Explain that ssh host keys provide the server identity to clients to establish trust and prevent man-in-the-middle attacks. Store the keys in /etc/ssh and use fingerprints to aid verification.

Learn how to assign the output of a command to a shell variable using command substitution, with the correct syntax mydate="$(date)" and the pitfalls of other methods.