Linux tutorial video notes

I was requested to make a summary of a video about basic Linux stuff (like the SQL tutorial video notes); this time, I did most of the notes depending on the topic since I’m familiar with most of the stuff presented in the video. The video in question is: The Complete Linux Course: Beginner to Power User!. Also, some notes were taken from Arch Linux Wiki since it’s got pretty decent documentation, and, of course, general googling.

(Basic) commands

A list of basic commands and small explanation (note that options are started with either - or --, depending on the program, but most of the time - is used for letter options and -- for word options, -l vs --list for example):

And in general, to see the options supported by almost any command, use command -h or command --help, for a quick explanation. IMPORTANT: Most programs have man (manual) pages; to access them do man command, this is a very powerful tool to use.

Commands can be redirected to other commands (the output), which is powerful to create mini scripts or to achieve a goal in a single command. Most of the time the redirection can be done with the special characters >, < and most powerful, the | (pipe). Also, some commands accept an option to execute another command, but this depends on a command to command basis (exec option for find, for example).

Most terminal programs accept Ctrl-c or just q to exit the program.

File permissions and ownership

When listing files with ls -l, an output with file attributes (permissions) and ownership is shown, such as drwxr-xr-x 2 user group 4096 Jul 5 21:03 Desktop, where the first part are the attributes, and user and group the ownership info (all other info is irrelevant for now).

File attributes (drwxr-xr-x in the example above) are specified by 10 (sometimes 11) characters, and can be break into 4 parts (or 5):

Each of the three permission triads (rwx) can be:

To change attributes or ownership use chmod and chown, respectively.

Services

Special type of linux process (think of a program or set of programs that run in the background waiting to be used, or doing essential tasks). There are many ways to manage (start, stop, restart, enable, disable, etc.) services, the most common way (if using systemd) is to just use systemctl. Basic usage of systemctl is systemctl verb service, where verb could be start, enable, stop, disable, restart, etc. Also, to get a general system status run systemctl status or just systemctl for a list of running units (a unit is an instance of a service, or a mount point or even a device or a socket). For more: Arch Linux Wiki: systemd.

systemd also provides a way to do tasks based on a timer, where you can schedule from the second to the year. One could also use cron (using crontab with option e) to do this. These timers provide support for calendar time events, monotonic time events, and can be run asynchronously.

User and group management

Most mainstream linux distributions come with a Graphic User Interface (GUI) to manage users and groups on the system. For a Command-Line Interface (CLI) just use useradd (with passwd to create a password for a given user) and groupadd. Also, other useful commands are usermod, userdel, groups, gpasswd, groupdel and more, each used for a basic management of users/groups like modification, deletion, listing (of all existing users/groups), etc.. For more: Arch Linux Wiki: Users and groups.

Networking

Hosts file

Located at /etc/hosts, serves as a translator from hostname (web addresses or URLs) into IP addresses (think of DNS records), meaning that any URL can be overridden to make it point to whatever IP address it’s specified (only locally on the machine affected). The syntax of the file is pretty simple: first column for IP, second for hostname (URL) and third+ for aliases.

(Some) commands

These commands serve the sole purpose of showing information about the network and stuff related to it:


By: David Luévano

Created: Sun, Mar 14, 2021 @ 05:57 UTC

Edited: Mon, May 17, 2021 @ 20:59 UTC