Systemctl to disable service on boot

We will learn basic commands to manage systemd services and units using systemctl.

Using systemctl we can enable disable particular service to be started or stopped when system boot.

To check status of service use

systemctl status postfix.service

To stop service use

systemctl stop postfix.service

To start service

systemctl start postfix.service

To disable the service from starting automatically on boot, type:

systemctl stop postfix.service

and then

systemctl disable postfix.service

This will make sure service is stopped now and will not start automatically after server reboot.

If you want service should be started automatically when server boot you will need to enable it using following command.

systemctl enable postfix.service

Setup LAMP on centos 7

Here are steps provided to install LAMP on centos 7.

Check version of OS using command

cat /etc/redhat-release

Command to install all packages required for Apache, mysql and php

yum install httpd php php-mysql mariadb-server -y

Let’s enable and start all services using commands

systemctl enable httpd mariadb

Now start httpd and mariadb services.

systemctl start httpd mariadb

Try to access your server IP in browser and you will find apache accessible.

To check php version execute following command

echo "<?php phpinfo(); ?>" > /var/www/html/phpinfo.php

Try to access this page using url

http://IP-of-machine/phpinfo.php

Let’s configure mysql service.

To configure MariaDB, run ‘mysql_secure_installation’

[root@midnight~]# mysql_secure_installation
/usr/bin/mysql_secure_installation: line 379: find_mysql_client: command not found

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MariaDB to secure it, we'll need the current
password for the root user.  If you've just installed MariaDB, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none):
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MariaDB
root user without the proper authorisation.

Set root password? [Y/n] Y
New password: NewPasswordHere
Re-enter new password: NewPasswordHere
Password updated successfully!
Reloading privilege tables..
 ... Success!


By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] Y
 ... Success!

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] Y
 ... Success!

By default, MariaDB comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] Y
 - Dropping test database...
 ... Success!
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] Y
 ... Success!

Cleaning up...

All done!  If you've completed all of the above steps, your MariaDB
installation should now be secure.

Thanks for using MariaDB!

 

Now your server is ready to host website supporting php and mysql database.

Restore a Deleted File in Linux

We will learn how to restore delete file in linux

Foremost is not available in any of the CentOS/RHEL repositories, so we’ll need to install it using RPM.

For centos 7 use following command

yum install https://forensics.cert.org/centos/cert/7/x86_64//foremost-1.5.7-13.1.el7.x86_64.rpm -y

For Centos 6 use following command

yum install https://forensics.cert.org/centos/cert/6/x86_64//foremost-1.5.7-13.1.el6.x86_64.rpm -y

Once formost installed let’s try to delete one file and recover it.

Get details of file midnight.jpg which we will delete and recover

file midnight.jpg
md5sum midnight.jpg

Now delete file

rm -f midnight.jpg

Restore a Deleted File

mkdir /root/recover
foremost -i /dev/sda1 -t jpg -o /root/recover/

Here -i used to specify disk and -t used to define type of file which we want to restore.
This command will find any .jpg files in /dev/sda1 and restore them into the /root/restored/ directory, as long as the space they are using on disk has not yet been overwritten by anything else.
Now go to /root/restored/jpg folder and execute md5sum 17602156.jpg and you will find md5 hash of this file is exactly same as that of midnight.jpg.