Linux System Administration I (Based on RHEL8)

Explore Linux as the leading open source operating system, its copyleft and permissive licenses like the GPL, and Red Hat Enterprise Linux's enterprise subscription model.

Master the bash shell and command line interface for Linux administration, including logging in, using the terminal, and essential commands like ls and pwd.

Log in to a linux server via putty or a physical console, recognize root's hash prompt versus normal user's prompt, and review home directories (/root, /home/username).

Explore how the linux shell executes commands by breaking them into command, option, and target, with examples like locking a user and using less for listings.

Learn to distinguish physical, virtual, and graphical consoles in Linux, access them via keyboard shortcuts like Ctrl+Alt+F1–F6, and switch between text and graphical logins.

explore the gnome 3 desktop as the default linux environment, log in, navigate the dash and activities, and learn to manage favorites and display server options.

Master basic Linux commands such as date for custom formats, passwd for changing passwords, and file for identifying file types and executables, with practices that enhance security.

Learn basic shell commands to view and edit files with cat and vi, inspect content with head and tail, analyze lines with wc, and navigate history with tab completion.

Learn tab completion to quickly complete commands and paths on the linux prompt, and master command-line editing with ctrl-a, ctrl-e, and ctrl-u to navigate and modify input.

explain linux file system hierarchy, detailing /boot, /bin, /sbin, /tmp, and /home, and describe how boot components like grub, kernel image, and initramfs load the system.

Explore how linux treats every object as a file, focusing on /dev device files. Learn that /etc stores local configuration, while /media and /mnt are mount points.

Explain the Linux filesystem hierarchy and inverted root structure, with root at the top and /home for user homes. Highlight how /root serves the root user’s home and FHS standard.

Describe how lib stores libraries and how /proc reveals live process data. Note /usr links to bin and lib, and /opt and /var store third-party and variable data.

Master essential linux command line file management by creating, deleting, copying, moving, and listing files and directories, including recursive and force options, and handling hidden files.

Learn how to specify file locations with absolute and relative paths, including how absolute paths start with a slash and how relative paths reference the current directory.

Manage files and directories in linux using command-line tools to create, copy, move, and delete items, with recursive, forceful options and visibility of hidden files.

Explore hard links and symbolic (soft) links in Linux, showing how multiple names reference the same data via inodes, cross-filesystem limits, and the effects on permissions and deletion.

Match file names with shell expansion and pattern matching to efficiently manage multiple files, using wildcards and single-character and multi-character patterns, and home directory and variable expansion.

Learn to get help in Linux with man pages, info pages, the whatis command, and keyword searches, through manual page sections 1 to 9, to navigate Red Hat Enterprise Linux.

Learn how to use the Linux man command to read and navigate manual pages, search content, and exit efficiently, with tips for jumping, scrolling, and locating options.

Learn how to use the info command to access hypertext information pages, navigate a documentation tree, and search commands and options through cross references and anchored keywords.

Use the whatis command to get a one-line description of any Linux command, see its manual page description, and learn common options such as enabling debugging output.

Explore input and output redirection in Linux, using files as standard input and redirecting or appending standard output to files with <, >, and >>.

Explore how to perform input and output redirection in Linux, redirecting standard output and standard error to files with > and >>, and understanding file descriptors.

Explore the Linux pipes feature, a redirection method that transfers a command's output to another command, enabling chaining like ls | less, grep, and wc -l for admin tasks.

Learn how the tee command duplicates standard output to the terminal and a file, enabling simultaneous display and redirection with pipes and examples.

Explore vim, the improved vi editor, with its four modes: insert, command, extended command, and visual, learned through creating and saving a file with basic commands like :wq.

Learn to use vim editor by switching between insert, command, and ex modes to write, edit, copy, paste, replace content, save, and quit files.

Master vim visual mode across character, line, and block modes. Use v, shift-v, and ctrl-v to select text, then delete, copy, or edit, and undo with u.

Examine bash variables in the linux shell, including environmental and system variables; define, display with dollar notation, and perform arithmetic, noting that variables are local to a single shell.

Define environmental variables with export, usually in capital letters, to set global shell settings across shell instances, including language (LANG) and home (HOME), and view or unset them with env.

Explore local user and group management in Linux, learn to distinguish super users, system users, and regular users, and manage privileges and UID ranges for secure administration.

Manage local Linux users and groups by creating users with useradd, setting passwords with passwd, and noting default /home directories and groups named after each user.

Explore user management in Linux system administration (based on RHEL8): learn how /etc/passwd and /etc/shadow store user data, the meaning of fields, and how password and expiry are handled.

Discover how the passwd and shadow files manage user accounts, including password storage with SHA-512, account lock with exclamation, and password aging fields.

This lecture explains the chage command for managing user password expiry, inactivity, and change intervals, including examples using -m, -M, -I, and -e and viewing with -l.

Explore how Linux uses primary and supplementary groups to manage file permissions, ownership, and access, with practical examples of assigning a primary group such as sales and enforcing group-based rights.

Understand how login.defs defines uid ranges for system and regular Linux accounts and directs user creation with useradd, including primary and supplementary groups and shadow file password storage.

Learn to manage linux users and groups from the command line, including creating and deleting users with or without home directories, renaming groups, changing gids, and inspecting /etc/passwd and /etc/group.

Understand how the sudoers file governs privileges, letting normal users perform privileged changes with their own credentials while auditing who makes each change on multiple servers.

Explore configuring sudo privileges in the sudoers file, granting specific users or groups access to run commands on selected hosts, and the syntax fields for user, host, runas, and commands.

Configure sudo access for a normal user by editing the sudoers file to grant full or restricted privileges and enable optional passwordless sudo, with actions logged under the invoking user.

Learn how Linux file permissions control access for owner, group, and others using read, write, and execute. The lecture explains interpreting ls -l output and absolute versus symbolic permission methods.

Apply chmod using the absolute method to set owner, group, and others permissions with octal values like 700, 777, and 000, using ls -l to verify.

Learn how to use chown to change a file’s owner and group from root to another user, enabling that user to manage the file.

Learn to manage file permissions from the command line by creating groups, adding users, and assigning owner and group rights for read and write access.

Learn to modify file permissions using symbolic mode with user, group, and others, employing plus, minus, and equals to add, remove, or set read, write, and execute rights.

Learn how suid and sgid bits enable a user process to perform actions with owner or group privileges, as shown when passwd updates /etc/shadow under root privileges.

Learn to set the setuid bit with chmod in absolute and symbolic modes, and read how owner, group, and others execute permissions display as s or S.

Set the setgid bit on a file or directory to grant the directory's group ownership to new files, using chmod g+s and observing the s bit in permissions.

Apply the sticky bit to publicly accessible directories to prevent other users from deleting a user's files, using chmod and directory examples to illustrate behavior.

Learn how the Linux kernel manages processes from creation to termination, including foreground and background tasks and states like new, ready, running, waiting, and terminated, with memory and I/O management.

Learn how the kernel communicates with processes by examining process states and status codes with top and ps, including running, ready, sleeping, zombie, stopped, and exit states.

Explore the top command for a real-time view of Linux processes, including CPU and memory usage, load averages, and foreground versus background task management.

Use the top command to monitor Linux processes in real time, view CPU and memory usage, adjust refresh intervals, sort by priority, and kill processes when needed.

learn to manage processes with the ps command, view pid and terminal, monitor cpu and memory usage, and tailor output with options like aux, -e, -f, and -l.

Learn to work with foreground and background processes, using ps and top to monitor, kill, and manage parent and child processes across terminals.

Learn to manage Linux processes with kill signals, and identify processes using ps and grep. Understand default SIGTERM and forced SIGKILL via kill -9.

Explore how systemd manages Linux starting processes and daemons, highlighting parallel startup, automatic restarts, resource control with cgroups, on-demand service start, and unit types like service, socket, and path.

Explore systemd with systemctl to manage service units, sockets, and targets; learn to list, check status, start, stop, restart, enable, and disable services on RHEL8.

Learn to set run levels with systemd targets using systemctl and symbolic links, switching between graphical, multi-user, and rescue targets, and view the system default target.

Set up runlevel with a symbolic link to the multi-user target in systemd and set the default to multi-user without graphics. List active targets to verify the runlevel.

Switch from multi-user to graphical runlevel by setting the graphical target as default with systemd; learn how service moves to systemctl for managing network-manager and enabling read-ahead.