Linux directory architecture More Details

Directory	Details source
/	Primary hierarchy root and root directory of the entire file system hierarchy.
/bin	Essential software typically needed to get the system running.
/boot	Files related to the boot menu/loader. Holds the file to boot the operating system.
/dev	Virtual files representing hardware devices.
/etc	Contains all the configuration files.
/home	User's personal folder. If we create user, it will create a folder inside the home directory using that username.
/lib	Support or library files required by software or applications. Kernel modules and shared libraries.
/media	Contains sub folders where storage device can be mounted. Temporary removable devices eg. CD RAM, USB, Floppy Disk.
/proc	Virtual folder containing files representing stats and settings.
/root	Personal folder for root user.
/sbin	Essential software for system maintenance, used only for the root user.
/tmp	Temporary files/folders.
/usr	Essentially, subdirectories containing most software used on the system, including system libraries and documentation.
/var	Data that is vital to the running of the system and that is constantly being updated.

Some Centos 7 command

1. Graphical interface

ctrl+alt+f1

2. Command line interface

ctrl+alt+f2

3. Login with same user as Command line interface

ctrl+alt+f3

4. To clear the screen

ctrl+l

5. To see the hosts

nano /etc/hosts

6. To see the terminal

tty

7. To see the CentOS version

hostnamectl 

8. Show Files and directories

Commands	Details
ls -a	Show all including hidden files, not show file size
ls -la	List all including hidden files, with bytes formatted file size
ls -lh	List only human created files, with well formatted file size
ls -lSh	List only human created files, with well formatted file size with sort
ls -i	Show files with id number
ls -li	List files with id number
ls -F	Show the all folders
ls -Fl	List the all folders
ls -r	Show all files in reverse order
ls -lr	List all files in reverse order
ls -R	Show subdirectory recursively
dir -Shli	List directory with shorted, human and id set
ls -ltr	Show the file and directory with latest modification of date and time
ls -l director_name	To show the file of a specific directory
dir -l /	To show the all directories inside root directory
dir -al /	To show the all directories inside root directory with hidden files
dir -nl --author	To show the all files group by user
dir -amil	To show the all files and folders that have hidden files
dir -amli /	To show the all files and folders that have hidden files inside root folder
dir -dl /etc	Show the directory with permission, who is the owner of that directory

9. Show the block device as tree structure and list structure.

lsblk 
lsblk -l

10. History or show to all executed command

history 

11. Create a directory

mkdir directory_name
mkdir -p dir1/dir2/dir3 [To create nested directory]

12. Create a file

touch file_name
touch file{1..5}.txt [Create files with file name = file1.txt to file5.txt]

13. See the file content

cat file_name

14. To add some data in a file

cat > file_name

Write something and press ctrl+d to close.

15. To join multiple files in one file

cat file1, file2, file3 > file_name.txt

16. To see the calendar

call

17. To see calendar for a specific month and year

cal 09 1994

18. To see the today's date

date

19. To get the basic calculator

bc

Linux-Basic-Command

Some Linux basic command for daily use

Install Full Webserver apache, php, mysql, phpmyadmin on ubuntu.

0. First Update sudo apt-get update
1. Install Apache sudo apt-get install apache2
2. Apache Config Test sudo apache2ctl configtest
3. Need to set server name sudo nano /etc/apache2/apache2.conf
4. Then need to paste ServerName 127.0.0.1 at the last line of apache2.conf file
5. Restart the apache server sudo systemctl restart apache2
6. Set permission to folder access sudo chmod 777 /var/www/html
7. Install mysql sudo apt-get install mysql-server
8. Mysql security issues sudo mysql_secure_installation
9. Install php sudo apt-get install php libapache2-mod-php php-mcrypt php-mysql
10. Add Index.php file first sudo nano /etc/apache2/mods-enabled/dir.conf
11. Restart Apache for current changes sudo systemctl restart apache2
12. Install phpmyadmin sudo apt-get install phpmyadmin
13. Open the file sudo nano /etc/apache2/apache2.conf and this Include /etc/phpmyadmin/apache.conf paste to the last line of the file.

Note: if face problem in mysql_secure_installation 0. SHOW VARIABLES LIKE 'validate_password%';

1. SET GLOBAL validate_password.LENGTH = 4;

2. SET GLOBAL validate_password.policy = 0;

3. SET GLOBAL validate_password.mixed_case_count = 0;

4. SET GLOBAL validate_password.number_count = 0;

5. SET GLOBAL validate_password.special_char_count = 0;

6. SET GLOBAL validate_password.check_user_name = 0;

7. ALTER USER 'user'@'localhost' IDENTIFIED BY 'pass';

8. FLUSH PRIVILEGES;

9. Change the project location in sudo nano /etc/apache2/sites-available/000-default.conf to DocumentRoot /home/juyel/www then this command sudo a2ensite 000-default.conf and sudo a2enmod rewrite finally sudo systemctl restart apache2

Some Linux Basic Command.

1. Upload file from local pc to remote scp -r /path/to/my/files root@0.0.0.0:/path/on/my/server

2. Download file from remote to local pc scp -r root@0.0.0.0:/path/on/my/server/file /path/to/my/path

3. Unzip a zip file first sudo apt install unzip then unzip test.zip

4. Installing Node.js with Apt Using a NodeSource PPA

   i. curl -sL https://deb.nodesource.com/setup_18.x -o nodesource_setup.sh

   ii. nano nodesource_setup.sh just see

   iii. sudo bash nodesource_setup.sh

   iv. sudo apt install nodejs

5. After add proxy to transfer http request to another port a2enmod proxy_http proxy headers session expires

6. Change Your default php version sudo update-alternatives --config php

There are 7 choices for the alternative php (providing /usr/bin/php).

  Selection    Path             Priority   Status
------------------------------------------------------------
  0            /usr/bin/php8.0   80        auto mode
  1            /usr/bin/php5.6   56        manual mode
  2            /usr/bin/php7.0   70        manual mode
* 3            /usr/bin/php7.1   71        manual mode
  4            /usr/bin/php7.2   72        manual mode
  5            /usr/bin/php7.3   73        manual mode
  6            /usr/bin/php7.4   74        manual mode
  7            /usr/bin/php8.0   80        manual mode

Press <enter> to keep the current choice[*], or type selection number: Here type the selection number and press enter

17. Install multiple version of php

sudo apt install php5.6 php5.6-fpm php5.6-mysql php5.6-sqlite3 php5.6-bcmath php5.6-gd php5.6-odbc php5.6-sybase php5.6-bz2 php5.6-gmp php5.6-opcache php5.6-tidy php5.6-cgi php5.6-imap php5.6-pgsql php5.6-xml php5.6-cli php5.6-interbase php5.6-phpdbg php5.6-xmlrpc php5.6-common php5.6-intl php5.6-pspell php5.6-xsl php5.6-curl php5.6-json php5.6-readline php5.6-zip php5.6-dba php5.6-ldap php5.6-recode php5.6-dev php5.6-mbstring php5.6-snmp php5.6-enchant php5.6-mcrypt php5.6-soap

sudo apt install php7.0 php7.0-fpm php7.0-mysql php7.0-sqlite3 php7.0-bcmath php7.0-gd php7.0-odbc php7.0-sybase php7.0-bz2 php7.0-gmp php7.0-opcache php7.0-tidy php7.0-cgi php7.0-imap php7.0-pgsql php7.0-xml php7.0-cli php7.0-interbase php7.0-phpdbg php7.0-xmlrpc php7.0-common php7.0-intl php7.0-pspell php7.0-xsl php7.0-curl php7.0-json php7.0-readline php7.0-zip php7.0-dba php7.0-ldap php7.0-recode php7.0-dev php7.0-mbstring php7.0-snmp php7.0-enchant php7.0-mcrypt php7.0-soap

sudo apt install php7.1 php7.1-fpm php7.1-mysql php7.1-sqlite3 php7.1-bcmath php7.1-gd php7.1-odbc php7.1-sybase php7.1-bz2 php7.1-gmp php7.1-opcache php7.1-tidy php7.1-cgi php7.1-imap php7.1-pgsql php7.1-xml php7.1-cli php7.1-interbase php7.1-phpdbg php7.1-xmlrpc php7.1-common php7.1-intl php7.1-pspell php7.1-xsl php7.1-curl php7.1-json php7.1-readline php7.1-zip php7.1-dba php7.1-ldap php7.1-recode php7.1-dev php7.1-mbstring php7.1-snmp php7.1-enchant php7.1-mcrypt php7.1-soap

sudo apt install php7.2 php7.2-fpm php7.2-mysql php7.2-sqlite3 php7.2-bcmath php7.2-gd php7.2-odbc php7.2-sybase php7.2-bz2 php7.2-gmp php7.2-opcache php7.2-tidy php7.2-cgi php7.2-imap php7.2-pgsql php7.2-xml php7.2-cli php7.2-interbase php7.2-phpdbg php7.2-xmlrpc php7.2-common php7.2-intl php7.2-pspell php7.2-xsl php7.2-curl php7.2-json php7.2-readline php7.2-zip php7.2-dba php7.2-ldap php7.2-recode php7.2-dev php7.2-mbstring php7.2-snmp php7.2-enchant php7.2-mcrypt php7.2-soap

sudo apt install php7.3 php7.3-fpm php7.3-mysql php7.3-sqlite3 php7.3-bcmath php7.3-gd php7.3-odbc php7.3-sybase php7.3-bz2 php7.3-gmp php7.3-opcache php7.3-tidy php7.3-cgi php7.3-imap php7.3-pgsql php7.3-xml php7.3-cli php7.3-interbase php7.3-phpdbg php7.3-xmlrpc php7.3-common php7.3-intl php7.3-pspell php7.3-xsl php7.3-curl php7.3-json php7.3-readline php7.3-zip php7.3-dba php7.3-ldap php7.3-recode php7.3-dev php7.3-mbstring php7.3-snmp php7.3-enchant php7.3-mcrypt php7.3-soap

sudo apt install php7.4 php7.4-fpm php7.4-mysql php7.4-sqlite3 php7.4-bcmath php7.4-gd php7.4-odbc php7.4-sybase php7.4-bz2 php7.4-gmp php7.4-opcache php7.4-tidy php7.4-cgi php7.4-imap php7.4-pgsql php7.4-xml php7.4-cli php7.4-interbase php7.4-phpdbg php7.4-xmlrpc php7.4-common php7.4-intl php7.4-pspell php7.4-xsl php7.4-curl php7.4-json php7.4-readline php7.4-zip php7.4-dba php7.4-ldap php7.4-dev php7.4-mbstring php7.4-snmp php7.4-enchant php7.4-mcrypt php7.4-soap

sudo apt install php8.0 php8.0-fpm php8.0-mysql php8.0-sqlite3 php8.0-bcmath php8.0-gd php8.0-odbc php8.0-sybase php8.0-bz2 php8.0-gmp php8.0-opcache php8.0-tidy php8.0-cgi php8.0-imap php8.0-pgsql php8.0-xml php8.0-cli php8.0-interbase php8.0-phpdbg php8.0-xmlrpc php8.0-common php8.0-intl php8.0-pspell php8.0-xsl php8.0-curl  php8.0-readline php8.0-zip php8.0-dba php8.0-ldap php8.0-dev php8.0-mbstring php8.0-snmp php8.0-enchant php8.0-mcrypt php8.0-soap