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1. Introduction to operating systems
While web developers primarily focus on coding web applications and front-end development, having a good grasp of operating systems is essential for ensuring the compatibility, security, performance, and reliability of their applications, as well as for troubleshooting and optimizing various aspects of web development.
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2. Introduction to data networks
Networking is an integral part of web development because web applications rely on network communication to function. A solid understanding of networking concepts and practices is essential for building secure, performant, and reliable web applications.
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3. The shell. Linux commands
Knowing Linux commands for a system administrator or even a software developer is of utmost importance because most servers run on a Linux or Unix operating system.
- 3.1 ls : showing files
- 3.2 file permissions
- 3.3 mkdir. Creating directories
- 3.4 rmdir. Deleting directories
- 3.5 Moving/renaming files and directories
- 3.6 Other commands
- 3.7 Mounting units
- 3.8 Daemons
- 3.9 What processes are running?
- 3.10 Who am I and where am I?
- 3.11 Files has its owner
- 3.12 Other commands
- 3.13 Users
- 3.14 The /etc/passwd file
- 3.15 The /etc/group file
- 3.16 Links
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4. Shell script
In this chapter I want you to learn shell script but based on examples. Once you see the example I will propose another very similar one. If you do it and it works great, that means that not only do you understand the exercise but you are able to perform similar exercises. Keep in mind that with shell scripts you have to be patient. Misplaced whitespace can even cause a script to not work. If that happens, take a deep breath, be patient and persist, you will surely find the solution to the problem.
- 4.1. Your first shell script
- 4.2. Adding comments to your shell script
- 4.3. Variables in bash
- 4.4. Functions in bash
- 4.5 Conditional sentences
- 4.6. Repetitive sentences. Loops
- 4.7. Returning to functions
- 4.8. Arguments passed to a shell script.
- 4.9. Interaction with the user.
- 4.10. Using bash as a calculator
- 4.11. The expr command
- 4.12. What is the exit command and exit status?
- 4.13. File comparisons.
- 4.14. Comparisons of integers.
- 4.15. The shift command.
- 4.16. The let command and the arithmetic operators.
- 4.17. Logical operators.
- 4.18. The generation of random numbers.
- 4.20. C-style variables.
- 4.21. Menus in shell scripts.
- 4.22. Length of a string.
- 4.23. Finding out the numerical position of a substring in a string.
- 4.24. Extraction of a substring.
- 4.25. Deleting a substring.
- 4.26. Replacing a substring.
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5. NETWORKING
3.13 Users
Linux, as a clone of Unix, a system born on the Internet, is designed to serve several users at the same time. For this, there is the “root” or superuser account, and the other system users accounts.
3.13.1 creating a user
To create a user, we type, logging in as root, “useradd” without the quotes plus the username. Ex:
useradd carlos
You will have created a user without an access code. It will be necessary to create an access key for the new user created and for that we will see the passwd command later
3.13.2 Deleting a user
To delete a user, simply write the command:
“userdel” and the username, example:
user del carlos
3.13.3 User change
su [options] [username]
With su we can login to the system as if we were another user.
If we type su user we will start a new shell as if we were the user usuario
Example:
su carlos
Once this is typed, it will ask us for the password of the user carlos. (root will not be prompted)
3.13.4 I want to change the password
passwd [user]
Users can change their password with this command.
Root can change the password of any user on the system.
3.13.5 Miscellany
Rebooting the system
- reboot
How much free memory do I have in the system?
- free
How much does this information occupy?
directory?
- du
How much space do I have left on the disk
hard?
- df -k .
Search for a file… Search for the file mio.txt in the /home/antonio directory:
- find /home/antonio –name my.txt
Search for the file mio.txt in the WHOLE system:
- find / –name of mine.txt
What will this file have…. Command: cat file_name
- cat mio.txt
It will show the content of the file mio.txt
Searching for strings in files: grep command Example:
- grep “sofia” file.txt
It will look for sofia in the file named file.txt
Will these two files be the same???
- diff file1 file2
The diff command compares the contents of any pair of files. It will tell us the lines that do not match. With this command we can know if our files are equal or they differ in some way.