I want to prevent a specific file or folder from being deleted, even with the root user.

Problem

How to stop Linux from erasing the file(s) or folder(s)?

Solution

In Linux, there are two commands you can use to prevent unauthorized changes, protect the critical file(s) or folder(s), and ensure the integrity of the system: the lsattr and chattr commands.

A. The lsattr command

To see the properties of files or directories on a file system that supports extended attributes, use the lsattr command. So, lsattr command displays special attributes that are not visible with the ls -l command. Run the command below to see the list of attributes:

lsattr

By default, if your server uses the ext4 format, a file or folder on that Linux server will have the e attribute, or extent format, which is a more efficient file storage method than the traditional block method. Below is a brief explanation of the various attributes:

File/Folder Attributes

B. The chattr command

With Linux, users can modify the properties of files and directories with the ‘chattr’ (change attribute) command. Using this command, you can protect a file or directory from deletion or addition, which is very useful for protecting critical files or folders. To use this command, you can follow the format below:

chattr [operator][attribute] file(s)/folder(s)

You can see the attributes in the table above, while the table below shows the operators you can use:

The Operators in attribute file(s)/folder(s)

1. Making a file undeletable

Use the command below to make a file undeletable in a file, for example, test.txt:

chattr +i test.txt

Then, try deleting the file. It should be undeletable even with the root user, as shown in the image below:

You cannot even rename the file or move it to another folder, as shown in the image below:

If you want to really delete a file, you have to run the command below, and you can delete the file like in the image below:

2. Append data without modifying existing data on a File

If you want the file to be able to add content without deleting the content that is already in the test.txt file, use the command below

chattr +a test.txt

Then try running the two commands below:

echo "Add test" > test.txt
echo "Just test" >> test.txt

And only the second command should be able to be executed, as shown in the image below:

To get the file back to “normal”, use the command below:

chattr -a test.txt

3. Making a folder secure

Use the command below if you want your folder to be undeleted, for example, the docs folder:

chattr -R +i docs/

Now, try to delete the folder, and it should not be deletable as shown in the image below:

Even you can’t delete the files in the folder, as shown in the image below:

For the folder to be deleted, use the command below:

chattr -R +i docs/

Note

You can run more than one option to change the attributes of a file in a command. For example, you want the file to be undeletable and appended without deleting the content that was previously present in the test.txt file, then use the command below:

chattr +ia test.txt

Likewise, you can delete more than one attribute for the test.txt file, then use the command below:

chattr -ia test.txt

You can also run and change the attribute in more than one file or folder. For example, you want to change the attributes for test.txt and ok.txt, use the following command:

chattr +ia test.txt ok.txt 

References

geeksforgeeks.org
tecmint.com
howtoforge.com

I want to access the user on the Ubuntu server that has the privilege of root using the sudo command, but I forgot my user password.

Problem

How to reset the password in Ubuntu?

Solution

Here are the steps to reset the password in Ubuntu:

1. Reboot the server

Reboot the server and press the Esc key or Shift key, and there should be a display like below:

2. Click the first option

To enter recovery mode, select the top part of the image above and push the e button, so that there will be a display like the image below:

Find the line starting with linux, similar to the picture below:

Remove everything from ro and append rw init=/bin/bash to the end of this line, like the picture below:

After you change the script, press F10 or Ctrl+x to boot these parameters.

3. Run the commands

In the recovery mode, run the command below:

mount | grep -w /

After that, execute the command below to change the password:

passwd 

After you change the password, run the commands below:

mount -o remount,ro /
exec /sbin/init

The Linux server will reboot, and after that, try to log in with the new password that you set before.

Note

By default, you cannot log in directly as root on Ubuntu, so you can’t change your password to root because to be root on Ubuntu, you only need to use your sudo command and enter your user password.

References

tecmint.com
askubuntu.com
infotechys.com

The previous article has explained how to display progress in a process, but unfortunately, this application is limited to displaying the copy and move process. This article will explain how to display a progress that not only displays the copy and move process, but can also display the backup process and restore a database.

Problem

How to display the progress bar in Linux commands?

Solution

By default, Linux commands do not display a progress bar, so you don’t know when the process is complete, like in the image below:

Therefore, Andrew Wood, An Experienced Unix Sysadmin, created an application to display a progress bar named Pipe Viewer or PV. To install the application, use the command below:

RockyLinux/AlmaLinux/CentOS

yum install epel-release
yum install pv

Ubuntu/Debian

sudo apt update
sudo apt install pv

OpenSUSE

sudo zypper install pv 

If you want to install pv applications in addition to the operating system shown above, you can go to this page. Here are some methods when using the pv application:

A. Copy

1. Copy the file

Use the format below to copy the file:

pv file1 > /folder/filename

So, if you want to copy an instances.sql to the /tmp folder, use the command below:

pv instances.sql > /tmp/instance.sql

2. Copy more than one file

If you want to copy more than one file to the folder, use the format below:

tar cf - file1 file2 file3 | pv | tar xf - -C /folder

Here is the command to copy more than one file to the /tmp folder

tar cf - babel.sql babel.sql.gz babel.sql.tar.gz  | pv | tar xf - -C /tmp

3. Copy the folder

If you want to copy the folder, use the format below:

tar cf - folder_name/ | pv | tar xf - -C /folder

If you want to copy the example folder to the /tmp folder, use the command below:

tar cf - example/ | pv | tar xf - -C /tmp

4. Copy more than one folder

If you want to copy more than one folder, use the format below:

tar cf - folder1/ folder2/ | pv | tar xf - -C /folder

So, if you want to copy more than one folder to the /tmp directory, use the command below:

tar cf - example/ test-project/ | pv | tar xf - -C /tmp

B. Move

If you want to use the move command on the PV application, then you can actually use the command to copy number 1, but add the command && rm -rf file1/folder1 behind it.

1. Move the file

So, if you want to move an instances.sql to the /tmp folder, use the command below:

pv instances.sql > /tmp/instance.sql && rm -rf instances.sql 

2. Move more than one file

If you want to move some files to the /tmp folder, use the command below:

tar cf - babel.sql babel.sql.gz babel.sql.tar.gz  | pv | tar xf - -C /tmp && rm -rf babel.sql babel.sql.gz babel.sql.tar.gz 

3. Move the folder

If you want to move a folder to the /tmp folder, use the command below:

tar cf - example/ | pv | tar xf - -C /tmp && rm -rf example/

4. Move more than one folder

If you want to move some folders to the /tmp folder, use the command below:

tar cf - example/ test-project/ | pv | tar xf - -C /tmp && rm -rf example/ test-project/ 

C. Compress

1. Using gz
Use the format below to run the gz command in pv application:

pv filename | gzip > filename.gz

For example, you want to compress babel.sql using gz, so use the command below:

pv babel.sql | gzip > babel.sql.gz

2. Using tar
Use the format below to run the tar command in pv application:

tar cf - filename | pv | gzip > filename.tar.gz

For example, you want to compress babel.sql using tar, use the command below:

tar cf - babel.sql | pv | gzip > babel.sql.tar.gz

3. Using bz2
Use the format below to run the tar command in pv application:

pv filename | bzip2 > filename.bz2

For example, you want to compress babel.sql using bz2, use the command below:

pv babel.sql | bzip2 > babel.sql.bz2

4. Using zip
Use the format below to run the tar command in pv application:

pv filename | zip filename.zip -q -

For example, you want to compress babel.sql using bz2, use the command below:

pv babel.sql | zip babel.sql.zip -q -

D. Extract

1. Using gunzip
Use the format below to extract the gz compression in pv application:

pv filename.gz | gunzip > filename

For example, you want to extract babel.sql.gz, so use the command below:

pv babel.sql.gz | gunzip > babel.sql

2. Using tar.gz
Use the format below to extract the gz compression in pv application:

pv filename.tar.gz | tar zxf -

For example, you want to extract babel.sql.tar.gz, so use the command below:

pv babel.sql.tar.gz | tar xzf -

3. Using bunzip2
Use the format below to extract the bz2 compression in pv application:

pv filename.sql.bz2 | bunzip2 > filename.sql

For example, you want to extract babel.sql.bz2, so use the command below:

pv babel.sql.bz2 | bunzip2 > babel.sql

4. Using unzip
Use the format below to extract the zip compression in pv application:

unzip filename.zip | pv

For example, you want to extract babel.sql.zip, so use the command below:

unzip babel.sql.zip | pv

E. Backup DB

If you use MariaDB, you can use the commands below:
1. Without compressing the database 
Use the format below to back up the database without compression in pv application:

mariadb-dump -u username -p dbname | pv > dbname.sql

So, use the command below to back up the database without compression in pv application:

mariadb-dump -uroot -p babel | pv > babel.sql

2. Back up the database using gz
Use the format below to back up the database using gz compression in pv application:

mariadb-dump -u username -p dbname | pv | gzip > dbname.sql.gz

Use the command below to back up the database using gz compression in pv application:

mariadb-dump -uroot -p babel | pv | gzip > babel.sql.gz

3. Backup the database using bz2
Use the format below to back up the database using bz2 compression in pv application:

mariadb-dump -u username -p dbname | pv | bzip2 > dbname.sql.bz2

Use the command below to back up the database using bz2 compression in pv application:

mysqldump -uroot -p babel | pv | bzip2 > babel.sql.bz2

F. Restore DB

If you use MariaDB, you can use the commands below:
1. Restore the database without compression
Use the format below to restore the database without compression in pv application:

pv backup_file.sql | mariadb -u username -p

So, use the command below to restore the database without compression in pv application:

pv babel.sql | mariadb -uroot -p

2. Restore the database with gz compression
Use the format below to restore the database using gz compression in pv application:

pv backup_file.gz | gunzip | mysql -u username -p

Use the command below to restore the database using gz compression in pv application:

pv babel.sql.gz | gunzip | mariadb -uroot -p 

3. Restore the database with bz2 compression
Use the format below to restore the database using bz2 compression in pv application:

pv backup_file.sql.bz2 | mariadb -u username -p

Use the command below to restore the database using bz2 compression in pv application:

pv babel.sql.bz2 | bunzip2 | mariadb -uroot -p babel

Note

If you are using a MySQL database, then you can use the commands in point E to back up the database and the commands in point F to restore the database by changing the mariadb-dump command to mysqldump and changing the mariadb command to mysql.

References

superuser.com
howtogeek.com
dba.stackexchange.com
tecmint.com
catonmat.net

The previous articles have explained how to perform a database backup in MariaDB. This article will explain how to perform a database restore in MariaDB.

Problem

How to restore the database in MariaDB?

Solution

There are several methods to perform the database restore in MariaDB:

1. Restore the entire database

To restore the backup file of the entire database, use the format below:

mysql -u username -p < backup_file.sql

Use the command below if your backup file name is backup_all_databases.sql:

mysql -u root -p < backup_all_databases.sql

After you run the above command, the database will be restored in MariaDB as shown in the image below:

2. Restore a database

Use the following format to restore a database’s backup file:

mysql -u username -p -e'create database new_database;' < backup_file.sql

If you want to restore the nodes database, then you can use the command below:

mysql -uroot -p -e'create database nodes;' < backup_nodes_db.sql

After you run the command above, MariaDB will restore the database like in the image below:

3. Restore the table(s)

If you want to restore the table(s), you can follow the format below:

mysql -u username -p db_name < table_backup_file.sql

So, use the command below if you want to restore the tables in the nodes database:

mysql -u root -p nodes < table_backup_file.sql

4. Restore a compressed backup file

There are two methods to restore a compressed backup file:

a. Restore the .gz backup file

If you want to restore a .gz backup file, use the format below:

gunzip < database.sql.gz | mysql -u username -p -e'create database new_database;'

For example, if you want to restore a database that uses .gz compression, then use the command below:

gunzip < nodes_backup_db.sql.gz | mysql -u root -p -e'create database nodes;'

b. Restore the .gz backup file

If you want to restore a .bz2 backup file, use the format below (but make sure your server has already installed the bzip2 package):

bunzip2 < database.sql.bz2 | mysql -u username -p -e'create database new_database;'

For example, if you want to restore a database that uses .bz2 compression, then use the command below:

bunzip2 < nodes.sql.bz2 | mysql -u root -p -e'create database nodes;'

Note

You can restore a database backup file that is compressed using method number 4, whether you compress when backing up the database or after backing up the database.

References

mariadb.com
stackoverflow.com
serverfault.com
bitbook.io

I want to back up the database in MariaDB.

Problem

How to back up the database in MariaDB?

Solution

Before doing a backup, it is highly recommended to ensure that there are no transactions in the database. Maybe you can turn off the application that is connected to the database or turn off the connection to the database so that it will produce a good backup file. In this article, I have 3 databases to use as an example, like the image below:

And below are the commands to back up the MariaDB database:

1. Back up the entire database

If you want to back up all databases in MariaDB, use the format below:

mariadb-dump -u username -p --all-databases > backup_file_name.sql

So, run the command below to back up your entire database:

mariadb-dump -u root -p --all-databases > backup_all_databases.sql

2. Backup a database

If you want to back up a database in MariaDB, use the format below:

mariadb-dump -u username -p db_name > backup_file_name.sql

So, run the command below if you want to back up the nodes database:

mariadb-dump -u root -p nodes > backup_nodes_db.sql

3. Backup more than one database

If you want to back up more than one database, use the format below:

mariadb-dump -u username -p db1_name db2_name > backup_file_name.sql

So, if you want to back up the nodes and image databases, use the format below:

mariadb-dump -uroot -p --databases nodes image > backup_nodes_and_image_db.sql

4. Backup database only

When you back up a database, by default, the database will be backed up in its entirety, both the database and the database structure. But sometimes you just want to back up the database without the structure, so you can use the format below:

mariadb-dump -u username -p --no-create-db --no-create-info db_name > dbname_db_only.sql

So, if you want to back up the database only for the nodes database, you can use the command below:

mariadb-dump -u root -p --no-create-db --no-create-info nodes > nodes_db_only.sql

5. Backup the database structure only

If you want to back up the database structure only, without the need to back up the database, then you can use the format below:

mariadb-dump -u username -p -–no-data db_name > dbname_structure_only.sql

So, use the command below if you want to back up the structure only for the nodes database: 

mariadb-dump -u root -p --no-data nodes > nodes_structure_only.sql

6. Backup table only

If you want to back up the specific table only in a database, you can use the format below:

mariadb-dump -u username -p db_name table1 table2 > backup_table1_table2_dbname.sql

So, if you want to back up 2 tables in the nodes database for babel and category tables, use the command below:

mariadb-dump -uroot -p nodes babel category > backup_babel_category_nodes.sql

7. Backup with compression

By default, when people perform database backups, they will usually use .sql as an extension of the database backup file. But actually, you can compress the database backup files when you do a backup. There are 2 methods of compressing database backups, namely using the tar.gz method and the .bz2 method. If you want to use the first method, use the format below:

mariadb-dump -u username -p db_name | gzip -9 -c > db_backup_file.sql.gz

Suppose you want to compress the nodes database, then use the command below:

mariadb-dump -u root -p nodes | gzip -9 -c > nodesdb_backup_file.sql.gz

And if you want to use bz2 compression when backing up databases, then make sure that the bz2 package is already installed on your server. If the package is not already installed, use the command below:

RockyLinux/AlmaLinux/CentOS

dnf install bzip2

Ubuntu/Debian

sudo install bzip2

OpenSUSE

zypper install bzip2

After you install the package, try to back up your database using the format below:

mariadb-dump -u username -p db_name | bzip2 > database.sql.bz2

If you want to back up your database, for example nodes database, run the below command:

mariadb-dump -u root -p nodes | bzip2 > nodes_backup_db.sql.bz2

Below is a comparison image of the size of the backup file that does not use compression, uses .tar.gz compression, and .bz2 compression:

Note

You should know that the mariadb-dump command has many useful options, including the ‐-single-transaction and ‐-lock-tables options. If you have a database that uses the InnoDB storage engine, then you should use the ‐-single-transaction option because this option starts a transaction before dumping and reads data from a consistent snapshot without locking the tables for extended periods, allowing concurrent reads and writes. However, if you are using the MyISAM storage engine, you can use the ‐-lock-tables option when backing up the database in MariaDB. If your database has a different storage engine, it is recommended to back up the database partially; some tables that use InnoDB use the ‐-single-transaction option, and some tables that use MyISAM use the ‐-lock-tables option when backing up the database.

References

mariadb.com
tecmint.com
linode.com
serversforhackers.com

If you are a user of the MariaDB database, you should know about the term storage engine.

Problem

How to display the storage engine in MariaDB?

Solution

A database engine (or storage engine) is the underlying software component that a database management system (DBMS) uses to create, read, update, and delete (CRUD) data from a database. To see a list of all available storage engines on the server, use the command below in the MariaDB prompt:

SHOW ENGINES;

and it will appear as shown in the image below:

From the image above, you can see that InnoDB is the default storage engine in MariaDB. You can also use the command below to see the default storage engine in MariaDB:

SHOW GLOBAL VARIABLES LIKE 'default_storage_engine';

You can change the default storage engine by using the command below, which changes the default storage engine to MyISAM:

SET GLOBAL default_storage_engine='MyISAM';

Or you can use the below command if the session default storage engine supersedes the global default during this session:

SET SESSION default_storage_engine='MyISAM';

You should know that the storage engine is used per table and not per database, and to see it, you can use the command below:

SELECT TABLE_NAME, ENGINE
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'nodes';

and the result will look like below:

From the image above, it can be seen that all tables in the nodes database use InnoDB, so it can be said that the nodes database uses InnoDB. However, one database (schema) can have a table with a different engine, and the query below is the sample to create 2 tables that use different storage engines:

CREATE TABLE product (
    id INT PRIMARY KEY,
    name VARCHAR(100)
) ENGINE=InnoDB;

CREATE TABLE access_log (
    id INT PRIMARY KEY AUTO_INCREMENT,
    time DATETIME,
    user VARCHAR(50)
) ENGINE=MyISAM;

where the product table uses InnoDB and the table access_log uses MyISAM. If a database uses various storage engines and you want to know how many storage engines are used, you can use the query below:

SELECT ENGINE, COUNT(*) AS Number_of_tables
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'db_name'
GROUP BY ENGINE;

You can change the storage engine of a table by using the query below, for example, change it to MyISAM:

ALTER TABLE database_name.table_name ENGINE=MyISAM;

Note

As explained above, there are many storage engines that you can use. But before you decide to use a storage engine, you should first find out the advantages and disadvantages of each storage engine, and to briefly see the differences between storage engines in the image below:

And below is a flowchart to determine the storage engines you will use:

However, as far as I know, among the many choices of storage engines, generally people use 2 types of storage engines, namely InnoDB and MyISAM. Maybe you can see the difference between the two through this site.

References

By default, in MariaDB, 4 databases are automatically created by the database system, namely information_schema, mysql, performance_schema, and sys. But I just want to display a database created by the user and not the default system databases.

Problem

How to display all databases created by the user in MariaDB?

Solution

If you use the show databases command after you access successfully accessing MariaDB, it will display all databases created by the user and default system databases, as shown below:

If you want to list only User-Created Databases, you can use a query as below:

SELECT SCHEMA_NAME
FROM information_schema.SCHEMATA
WHERE SCHEMA_NAME NOT IN ('information_schema','mysql','performance_schema','sys');

and it will display like the image below:

Note

If you want to run the Linux command to display all databases created by the user only, use the command below:

mysql -u root -p -e "SELECT SCHEMA_NAME FROM information_schema.SCHEMATA WHERE SCHEMA_NAME NOT IN ('information_schema','mysql','performance_schema','sys');"

And you will see the result like the image below:

References

stackoverflow.com
kinsta.com