Category Archives: Linux

Discover DevOps roles and learn Linux from basics to advanced at DevOpsRoles.com. Detailed guides and in-depth articles to master Linux for DevOps careers.

Linux

Centos 8 LEMP WordPress

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In this tutorial, How to Install and configure LEMP WordPress running a Centos 8. LEMP is an acronym for Linux, Nginx, MySQL, and PHP. Now, let’s go to Centos 8 LEMP WordPress.

Centos 8 LEMP WordPress Environment

  • Centos 8
  • Nginx
  • MySQL
  • WordPress

1.Nginx Install

The first, Your update for Centos 8.

[root@DevopsRoles vagrant]# dnf update

Next, Install Nginx on Centos 8

[root@DevopsRoles vagrant]# dnf install nginx
# Set to start automatically at reboot 
[root@DevopsRoles vagrant]# systemctl enable  --now nginx
# Check status
[root@DevopsRoles vagrant]# systemctl status nginx

Firewall port setting HTTP (80) Allow HTTPS(443)

[root@DevopsRoles vagrant]# firewall-cmd --add-port=80/tcp --permanent
[root@DevopsRoles vagrant]# firewall-cmd --reload

2.Install MySQL

[root@DevopsRoles vagrant]# dnf install @mysql
 # After installation, familiar service start, and automatic start setting
[root@DevopsRoles vagrant]# systemctl start mysqld
[root@DevopsRoles vagrant]# systemctl enable mysqld
 # The initial security settings of mysql
[root@DevopsRoles vagrant]# mysql_secure_installation
# Operation check
[root@DevopsRoles vagrant]# mysql -u root -p

3.Install PHP

[root@DevopsRoles vagrant]# dnf install php-fpm php-cli php-json php-opcache php-xml php-gd php-curl
# php is also set to start automatically
[root@DevopsRoles vagrant]# systemctl enable --now php-fpm

Extension php required to run WordPress on Centos 8

[root@DevopsRoles vagrant]# dnf install php-cli php-json php-opcache php-xml php-gd php-curl php-mysqlnd

4.Database Creation

[root@DevopsRoles vagrant]# mysql -u root -p
# db creation (name can be anything)
SQL> create database wordpressdb;
# Create user, set permissions and reflect settings
SQL> create user wpadmin@localhost identified by 'Stro123@.';
SQL> grant all on wordpressdb.* to wpadmin@localhost;
SQL> flush privileges;
SQL> quit

5.Install WordPress

# Download wordpress
[root@DevopsRoles vagrant]# wget https://wordpress.org/latest.tar.gz
# Create a folder for #wordpress
[root@DevopsRoles vagrant]# mkdir /usr/share/nginx/wp.devopsroles.com
# Decompress
[root@DevopsRoles vagrant]# tar xzf latest.tar.gz -C /usr/share/nginx/wp.devopsroles.com/ --strip-components=1
# Copy configuration file
[root@DevopsRoles vagrant]# cp /usr/share/nginx/wp.devopsroles.com/wp-config-sample.php /usr/share/nginx/wp.devopsroles.com/wp-config.php
# Open configuration file
[root@DevopsRoles vagrant]# vi /usr/share/nginx/wp.devopsroles.com/wp-config.php

Look like wp-config.php file as below:

/** MySQL database name */
define( 'DB_NAME', 'wordpressdb' );
/** MySQL database user name */
define( 'DB_USER', 'wpadmin' );

/** MySQL database password */
define( 'DB_PASSWORD', 'Stro123@.' );

/** MySQL hostname */
define( 'DB_HOST', 'localhost' );

/** Database character set when creating database table */
define( 'DB_CHARSET', 'utf8' );

/** Database collation (should not be changed in most cases) */
define( 'DB_COLLATE', '' );

Get the authentication unique key for WordPress.

curl -s https://api.wordpress.org/secret-key/1.1/salt/

Copy and paste the returned contents into wp-config.php

define('AUTH_KEY',         'balabal');
define('SECURE_AUTH_KEY',  'balabal');
define('LOGGED_IN_KEY',    'balabal');
define('NONCE_KEY',        'balabal');
define('AUTH_SALT',        'balabal');
define('SECURE_AUTH_SALT', 'balabal');
define('LOGGED_IN_SALT',   'balabal');
define('NONCE_SALT',       'balabal');

6.Nginx Settings

I have configured Nginx for WordPress with content as below:

vi /etc/nginx/conf.d/devopsroles.conf

server {
    listen       80 default_server;
    server_name  devopsroles.com;
    root         /usr/share/nginx/wp.devopsroles.com;

    access_log /var/log/nginx/access_devopsroles.com.log;
    error_log /var/log/nginx/error_devopsroles.com.log;

    index   index.php;

    location / {
        try_files    $uri $uri/ /index.php?$args;
    }
    location ~ \.php$ {
        fastcgi_pass unix:/run/php-fpm/www.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
        fastcgi_index index.php;
    }
    error_page 404 /404.html;
        location = /40x.html {
    }

    error_page 500 502 503 504 /50x.html;
        location = /50x.html {
    }
}

Set user and group nginx for the folder as below

chown -R nginx:nginx /usr/share/nginx/wp.devopsroles.com/

Restart Nginx

systemctl restart nginx

I have installed success Centos 8 LEMP WordPress. Have a good nice 🙂 Thank you for reading the DevopsRoles page!

Linux

Using Netdata to Monitor PHP-FPM

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In this tutorial, How to Monitor the PHP-fpm using Netdata on Centos 7. Netdata is a free open source. It is very easy to install and configure for real-time monitoring. Now, let’s go to Netdata to Monitor PHP-FPM.

PHP-FPM (FastCGI Process Manager) is an alternative PHP FastCGI. It is commonly used in LEMP ( Linux Nginx MySQL/MariaDB PHP) stack; Nginx uses PHP FastCGI for serving dynamic HTTP content.

Steps install and configure

  • Centos 7 Server or RHEL 7 Server
  • Install PHP and enable PHP-FPM status
  • Install Netdata and configure Monitor for PHP-FPM status.

1. How to Install PHP

For example, How to install PHP version 7.3 on Centos 7.

2. Enable the PHP-FPM status page.

Check php-fpm running on your system.

[root@DevopsRoles vagrant]# netstat -nplt | grep php-fpm
tcp        0      0 127.0.0.1:9000          0.0.0.0:*               LISTEN      4328/php-fpm: maste 
[root@DevopsRoles vagrant]# ps -ef | grep php
root      4328     1  0 21:50 ?        00:00:00 php-fpm: master process (/etc/opt/remi/php73/php-fpm.conf)
apache    4329  4328  0 21:50 ?        00:00:00 php-fpm: pool www
apache    4330  4328  0 21:50 ?        00:00:00 php-fpm: pool www
apache    4331  4328  0 21:50 ?        00:00:00 php-fpm: pool www
apache    4332  4328  0 21:50 ?        00:00:00 php-fpm: pool www
apache    4333  4328  0 21:50 ?        00:00:00 php-fpm: pool www
root      4381  3003  0 21:52 pts/0    00:00:00 grep --color=auto php

Configure file php-fpm status as shown.

$ sudo vim /etc/php-fpm.d/www.conf 
OR
$ sudo vim /etc/opt/remi/php73/php-fpm.d/www.conf	#for PHP versions 7.0, 7.1,7.3 vvv

You find and uncomment the variable pm.status_path = /status as shown in the screenshot.

[root@DevopsRoles vagrant]# cat /etc/opt/remi/php73/php-fpm.d/www.conf | grep pm.status_path
pm.status_path = /status

Save the changes and exit the file.

Check the PHP-FPM configuration file for any errors

$ sudo php-fpm -t
OR
$ sudo systemctl restart php73-php-fpm

Create a new Nginx config for PHP-FPM as shown

[root@DevopsRoles ~]# vi /etc/nginx/conf.d/php-fpm.conf

# The content as below:

    server {

        listen       80;
        #listen       [::]:80 default_server;
        server_name  127.0.0.1;

    location  /status {
        access_log off;
        allow 127.0.0.1;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_index index.php;
        deny all;
        include fastcgi_params;
        fastcgi_pass 127.0.0.1:9000;
   }
   }

Reload PHP-FPM and Nginx config for changes to take effect.

[root@DevopsRoles ~]# systemctl reload php73-php-fpm
[root@DevopsRoles ~]# systemctl reload nginx

Now, Use the curl command to check php-fpm status.

root@DevopsRoles ~]# curl http://127.0.0.1/status
pool:                 www
process manager:      dynamic
start time:           18/Jul/2020:10:16:17 +0700
start since:          878
accepted conn:        14
listen queue:         0
max listen queue:     0
listen queue len:     128
idle processes:       4
active processes:     1
total processes:      5
max active processes: 1
max children reached: 0
slow requests:        0

Memo: meaning of different values of PHP-FPM Status

-pool – the name of the pool.
-process manager – possible values static, dynamic or ondemand. We never use static.  Trying ondemand is on todo list.
-start time – the date and time FPM has started or reloaded.
-start since – number of seconds since FPM has started
-accepted conn – the number of request accepted by the pool
-listen queue – the number of request in the queue of pending connections. If this number is non-zero, then you better increase number of process FPM can spawn.
-max listen queue – the maximum number of requests in the queue of pending connections since FPM has started
-listen queue len – the size of the socket queue of pending -connections
-idle processes – the number of idle processes
-active processes – the number of active processes
-total processes – the number of idle + active processes
-max active processes – the maximum number of active processes since FPM has started
-max children reached – number of times, the process limit has been reached, when pm tries to start more children. If that value is not zero, then you may need to increase max process limit for your PHP-FPM pool. Like this, you can find other useful information to tweak your pool better way.
-slow requests – Enable php-fpm slow-log before you consider this. If this value is non-zero you may have slow php processes. Poorly written mysql queries are generally culprit.

3. Install Netdata on Centos 7 here

4. Configure Netdata to Monitor PHP-FPM

The Netdata configure for Nginx in folder /etc/netdata/python.d which is written in YAML format.

You can open it or create a new file php-fpm.conf as shown

[root@DevopsRoles python.d]# cat /etc/netdata/python.d/php-fpm.conf 
# The output as below:
localhost:
  name : 'local'
  url  : 'http://localhost/status'

localipv4:
  name : 'local'
  url  : 'http://127.0.0.1/status'

Restart Netdata Server

[root@DevopsRoles ~]# systemctl restart netdata

5. Using Netdata to Monitor PHP-FPM

Open a web browser access the netdata web UI.

http://NETDATA_SERVER_IP:19999
or
http://DOMAIN_NAME:19999

The result as the picture below

Conclusion

Through the article, you can use Netdata to monitor PHP-FPM. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Using Netdata to Monitor Nginx

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In this tutorial, How to Monitor the Nginx using Netdata on Centos 7. Netdata is a free open source. It is very easy to install and configure for real-time monitoring.

Steps install and configure

  • Centos 7 Server or RHEL 7 Server
  • Install Web Server Nginx
  • Install Netdata and configure Monitor for Web Server Nginx.

1. Install Web Server Nginx

Enable EPEL repository

[root@DevopsRoles ~]# yum install epel-release

Install the Nginx package, as follows.

[root@DevopsRoles ~]# yum install nginx

Start and enable Nginx Web Server, as follows.

[root@DevopsRoles ~]# systemctl start nginx
[root@DevopsRoles ~]# systemctl enable nginx
[root@DevopsRoles ~]# systemctl status nginx

If you are running a firewall. You need to open port 80/443 for Nginx Webserver.

Enable Nginx Stub_Status Module

I will enable the stub_status module which netdata uses to collect metrics from your Nginx web server.

[root@DevopsRoles ~]# vi /etc/nginx/nginx.conf

Copy and paste the location configuration as below

location /server_status {
 	stub_status;
 	allow 127.0.0.1;	#only allow requests from localhost
 	deny all;		#deny all other hosts	
 }

restart the Nginx service to effect

[root@DevopsRoles ~]# nginx -t
[root@DevopsRoles ~]# systemctl restart nginx

Now, Use curl command to check 

curl http://127.0.0.1/server_status

# The output terminal as below:
[root@DevopsRoles ~]# curl http://127.0.0.1/server_status
Active connections: 1 
server accepts handled requests
 1 1 1 
Reading: 0 Writing: 1 Waiting: 0

3. Install Netdata on Centos 7 here

4. Configure Netdata to Monitor Nginx

The Netdata configure for Nginx in folder /etc/netdata/python.d which is written in YAML format.

You can open it or create a new file nginx.conf as below

[root@DevopsRoles python.d]# cat /etc/netdata/python.d/nginx.conf 
# The output as below:
localhost:
  name : 'local'
  url  : 'http://localhost/server_status'

localipv4:
  name : 'local'
  url  : 'http://127.0.0.1/server_status'

Restart Netdata Server

[root@DevopsRoles ~]# systemctl restart netdata

5. Using Netdata to Monitor Nginx Web Server

Open a web browser access the netdata web UI.

http://NETDATA_SERVER_IP:19999
or
http://DOMAIN_NAME:19999

The result as the picture below

Conclusion

Through the article, you can use Netdata to monitor Nginx. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Using Netdata to Monitor MariaDB Database

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In this tutorial, How to Monitor the MariaDB database using Netdata on Centos 7. Netdata is a free open source. It is very easy to install and configure for real-time monitoring.

Steps install and configure

  • Centos 7 Server or RHEL 7 Server
  • Install MariaDB Database
  • Install Netdata and configure Monitor for MariaDB Database.

1. Install MariaDB Database

Adding MariaDB YUM software repository.

[root@DevopsRoles ~]# vim /etc/yum.repos.d/MariaDB.repo

The content file MariaDB.repo is as follows.

[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.1/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

Install the MariaDB package, as follows.

[root@DevopsRoles ~]# yum install MariaDB-server MySQL-python MariaDB-client -y

Start and enable MariaDB Database Server, as follows.

[root@DevopsRoles ~]# systemctl start mariadb
[root@DevopsRoles ~]# systemctl enable mariadb
[root@DevopsRoles ~]# systemctl status mariadb

By default, the MySQL installation is unsecure and you need to secure it, as follows

[root@DevopsRoles ~]# mysql_secure_installation

To create this user MariaDB

MariaDB [(none)]> create user 'netdata'@'localhost'; 
MariaDB [(none)]> grant usage on *.* to 'netdata'@'localhost'; 
MariaDB [(none)]> flush privileges;

If you are running a firewall. You need to open the port 3306 for MariaDB Database

3. Install Netdata on Centos 7 here

4. Configure Netdata to Monitor MariaDB

The netdata configure for MariaDB in folder /etc/netdata/python.d which is written in YAML format.

You can open it or create a new file mysql.conf as below

[root@DevopsRoles python.d]# cat /etc/netdata/python.d/mysql.conf 
localhost:
  name : 'local'
  user : 'netdata'
  port : '3306'

Restart Netdata Server

[root@DevopsRoles ~]# systemctl restart netdata

5. Using Netdata to Monitor MariaDB Database

Open a web browser access the netdata web UI.

http://NETDATA_SERVER_IP:19999
or
http://DOMAIN_NAME:19999

The result as the picture below

Netdata debug for mariadb

/usr/libexec/netdata/plugins.d/python.d.plugin 1 debug mysql

Error netdata for MariaDB code (Fixed)

2020-07-05 16:32:37: python.d ERROR: mysql[localhost] : MySQLdb or PyMySQL module is needed to use mysql.chart.py plugin

On My Centos missing MySQL-python package

Conclusion

Through the article, you can use Netdata to Monitor MariaDB Database. I hope will this your helpful.

Linux

Using Netdata to Monitor Apache Performance

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In this tutorial, How to Monitor Apache Performance using Netdata on Centos 7. Netdata is a free open source. It is very easy to install and configure for real-time monitoring.

Steps install and configure

  • Centos 7 Server or RHEL 7 Server
  • Install Apache HTTP Server with mod_status_module enabled
  • Install Netdata and configure Monitor for Apache HTTP Server.

1. Install Apache HTTP server

First, install the Apache HTTP server on Centos. I will Yum package manager to install Apache.

[root@DevopsRoles ~]# yum install httpd

Start and enable Apache HTTP server.

[root@DevopsRoles ~]# systemctl start httpd
[root@DevopsRoles ~]# systemctl enable httpd
[root@DevopsRoles ~]# systemctl status httpd

If you are running a firewall. You need to open ports 80 and 443 for Apache.

2. Enable mod_status module in Apache

You need to enable and configure the mod_status module in apache, This is required by Netdata.

[root@DevopsRoles ~]# cat /etc/httpd/conf.modules.d/00-base.conf | grep mod_status
LoadModule status_module modules/mod_status.so

Create a server-status.conf for the Apache server-status page as below

[root@DevopsRoles ~]# cat /etc/httpd/conf.d/server-status.conf
<Location "/server-status">
    SetHandler server-status
    #Require host localhost           #uncomment to only allow requests from localhost 
</Location>

Restart Apache HTTP Server

[root@DevopsRoles ~]# systemctl restart httpd

Test working Apache Server status page.

[root@DevopsRoles ~]# curl http://localhost/server-status

3. Install Netdata on Centos 7 here

4. Configure Netdata to Monitor Apache Performance

The Netdata configure for Apache in folder /etc/netdata/python.d

You can open it or create new file apache.conf as below

[root@DevopsRoles ~]# cat /etc/netdata/python.d/apache.conf
localhost:
  name : 'local'
  url  : 'http://localhost/server-status?auto'

localipv4:
  name : 'local'
  url  : 'http://127.0.0.1/server-status?auto'

Restart netdata server

[root@DevopsRoles ~]# systemctl restart netdata

5. Using Netdata to Monitor Apache Performance

Open a web browser access the Netdata web UI.

http://NETDATA_SERVER_IP:19999
or
http://DOMAIN_NAME:19999

The result as below

Conclusion

Thought the article, you can use Netdata to monitor Apache Performance. I hope will this your helpful.

Linux

Step-by-Step Guide to Install Tomcat7, Java 1.8, and Solr on CentOS 7

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Introduction

In this tutorial, we’ll walk through the process of Install Tomcat7 , Java 1.8, and Solr on CentOS 7. First, ensure your system is up to date by running the necessary updates. Then, proceed to download and install Java 1.8, configuring the environment variables accordingly. Next, set up Tomcat 7, adjusting the necessary configurations for optimal performance.

Finally, integrate Solr into Tomcat to leverage its powerful search capabilities. Throughout the tutorial, I’ll provide step-by-step instructions to guide you seamlessly through each installation process. By the end, you’ll have a fully functional and efficient setup of Tomcat 7, Java 1.8, and Solr on your CentOS 7 system.

Install Tomcat7 java 1.8 and Sorl

Install Java 1.8 and Tomcat 7

sudo yum install java-1.8.0-openjdk*
sudo yum install tomcat
sudo firewall-cmd --zone=public --add-port=8080/tcp --permanent
sudo systemctl restart firewalld.service
sudo systemctl enable tomcat.service
sudo systemctl start tomcat

Download Ant and ivy used to compile Solr as well.

yum install wget
wget -P /home/vagrant/ http://archive.apache.org/dist/lucene/solr/4.10.2/solr-4.10.2-src.tgz
wget -P /home/vagrant/ https://downloads.apache.org//ant/binaries/apache-ant-1.10.8-bin.tar.gz
wget -P /home/vagrant/ https://downloads.apache.org/ant/ivy/2.4.0/apache-ivy-2.4.0-bin.tar.gz
cd /home/vagrant/
tar zxvf solr-4.10.2-src.tgz
tar zxvf apache-ant-1.10.8-bin.tar.gz
tar zxvf apache-ivy-2.4.0-bin.tar.gz

[vagrant@Server01 ~]$ cp apache-ivy-2.4.0/ivy-2.4.0.jar apache-ant-1.10.8/lib/

Setting environment variables

export ANT_HOME=/home/vagrant/apache-ant-1.10.8
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64/
export PATH=${PATH}:/${ANT_HOME}/bin/

Edit /etc/tomcat/server.xml file

<Connector port="8080" protocol="HTTP/1.1"
 connectionTimeout="20000"
 redirectPort="8443" URIEncoding="UTF-8" useBodyEncodingForURI="true" />

Compiling Solr

cd /home/vagrant/solr-4.10.2
ant clean
ant compile
cd solr
ant dist

logging settings

cp solr-4.10.2/solr/example/lib/ext/* /usr/share/tomcat/lib
cp solr-4.10.2/solr/example/resources/log4j.properties /usr/share/tomcat7/lib

Arrangement of War files and various

cp solr-4.10.2/solr/dist/solr-4.10.2-SNAPSHOT.war to /var/lib/tomcat/webapps/solr.war

Create a directory for solr.home

mkdir /var/lib/solr/home
chmod -R a+w /var/lib/solr/home
vi /var/lib/solr/home/solr.xml
<?xml version="1.0" encoding="UTF-8" ?>
<solr persistent="false">
  <cores adminPath="/admin/cores">
  <core name="test" instanceDir="test" config="solrconfig.xml" schema="schema.xml"/>
  </cores>
</solr>

Modify /etc/tomcat/tomcat.conf

JAVA_OPTS="${JAVA_OPTS} -Djavax.sql.DataSource.Factory=org.apache.commons.dbcp.BasicDataSourceFactory -Dsolr.solr.home=/var/lib/solr/home"

Create a directory for the core

mkdir /var/lib/solr/home/test
mkdir /var/lib/solr/home/test/conf
mkdir /var/lib/solr/home/test/data
chmod -R a+x /var/lib/solr/home/test/data
cp solr-4.10.2/solr/example/solr/collection1/conf/* /var/lib/solr/home/test/conf/

please edit as you like it.

vi /var/lib/solr/home/test/conf/solrconfig.xml
vi /var/lib/solr/home/test/conf/schema.xml

Conclusion

In this guide, we have successfully installed and configured Tomcat7, Java 1.8, and Solr on CentOS 7. By following the detailed steps outlined above, you should now have a fully functional setup that is ready for web application deployment and advanced search capabilities.

This combination of technologies provides a robust foundation for developing and managing enterprise-level applications. Remember to regularly update your software to ensure security and performance enhancements. If you encounter any issues or have further questions, don’t hesitate to consult the official documentation or seek help from the community. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Mastering the rev command in Linux: Reversing Text Lines

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Introduction

In this guide, we’ll explore how to use the rev command in Linux, a powerful tool for reversing the characters in each line of text. Essential for many DevOps roles, the rev command enhances file manipulation and helps in reversing outputs from other commands. Let’s dive into how this simple yet effective command can streamline your text-processing tasks in Linux environments.

The syntax rev command in Linux

rev [option] [file...]

Some common options for the “rev” command include:

  • -V: Displays the version information for the command.
  • -h: Shows the help information.
  • -c: Treats input as single characters instead of entire lines.

In the manual page, the rev command is described succinctly as a utility to “reverse lines character-wise.” For comprehensive information about the rev command, including its options and examples, refer to the man page by entering man rev in the terminal. This will provide detailed insights into its functionality and usage.

For example rev command

Using the rev command reverses the output of the hostname command as below

[root@ip-10-0-0-236 ~]# hostname
ip-10-0-0-236.us-east-2.compute.internal
[root@ip-10-0-0-236 ~]# hostname | rev
lanretni.etupmoc.2-tsae-su.632-0-0-01-pi
[root@ip-10-0-0-236 ~]#

How to get 8 last characters use the combine rev command and cut command.

[root@ip-10-0-0-236 ~]# hostname
ip-10-0-0-236.us-east-2.compute.internal
[root@ip-10-0-0-236 ~]# hostname | rev | cut -b 1-8 | rev
internal

Sorting File Lines by Last Character

[ec2-user@ip-172-31-45-95 ~]$ cat domain.txt
devopsroles.com
abc.xyz
huuphan.com

[ec2-user@ip-172-31-45-95 ~]$ cat domain.txt  | rev | sort | rev
huuphan.com
devopsroles.com
abc.xyz

Conclusion

Throughout this article, you’ve seen how to utilize the rev command to Reverse characters Linux command. It’s important to remember that the rev command does not alter the original file; it merely displays the reversed output in the terminal or saves it to a new file. I hope you find these examples helpful for mastering the rev command. Thank you for reading at DevopsRoles!

Linux

Things to do in the initial configuration of CentOS 7

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What do you need to do in the initial configuration of CentOS 7? In this tutorial, Step by step I think need the initial configuration for Centos 7.

The initial configuration of CentOS 7

Time synchronization.

Setting Command history

The command in the example ( date, history,w, top, df) does not remain in the command history.

# cat << "_EOF" > /etc/profile.d/history.sh && source /etc/profile.d/history.sh

# The content command history
 HISTTIMEFORMAT='%F %T '
 HISTSIZE=100000
 HISTFILESIZE=100000
 HISTIGNORE='date,history:w:top:df'
 HISTCONTROL=ignoreboth
 PROMPT_COMMAND='history -a; history -c; history -r'
 _EOF

Enable i-search

Ctrl + r switches to the command history search mode, but by default, it cannot be re-searched in the reverse direction.

# echo '[ -t 0 ] && stty -ixon' > /etc/profile.d/stty.sh && source /etc/profile.d/stty.sh

Writing outputs to log file and console

cat << "_EOF_" > /etc/profile.d/script.sh && source /etc/profile.d/script.sh
# output operation log 
P_PROC=`ps aux | grep $PPID | grep sshd | awk '{ print $11 }'`
if [ "$P_PROC" = sshd: ]; then
  script -q /var/log/script/`whoami`_`date '+%F_%H%M%S'`.log
  exit
fi
_EOF_

# chmod 777 /etc/profile.d/script.sh

Monitor User Activity with psacct

You can use the lastcomm command to check which user executed which command when.

# yum -y install psacct && systemctl start $_ && systemctl enable $_

Detection with OSSEC HIDS

# yum install -y epel-release wget && curl -s http://www.atomicorp.com/installers/atomic | sh && yum install -y ossec-hids-server /var/ossec/bin/ossec-configure
# sed -i.org '/directories check_all/s/"yes"/"yes" realtime="yes"/' /var/ossec/etc/ossec.conf
# systemctl start ossec-hids && systemctl enable $_

Install and enable AIDE

Update Your System

# yum clean all && yum -y update

Prohibit login without password

# sed -i 's/\<nullok\>//g' /etc/pam.d/system-auth

su and sudo settings

# sed -i.org '/NOPASSWD/ s/^# //' /etc/sudoers
# sed -i.org '/use_uid/ s/^#//' /etc/pam.d/su

sudo without password

Modify /etc/sudoers file

%wheel ALL=(ALL)       NOPASSWD: ALL

Passwordless root switch

Modify /etc/pam.d/su file

auth           sufficient      pam_wheel.so trust use_uid

su authorized user limit

modify /etc/pam.d/su file

auth           required        pam_wheel.so use_uid

Adding administrative users

# useradd huupv && passwd $_ && usermod -G wheel $_ && getent group wheel
# sudo -u huupv echo 'huupv@devopsroles.com' > ~/.forward
# sed -i /etc/aliases -e '/root:/ s/^#//' -e '/root:/ s/marc/huupv/' && newaliases
# echo "Test mail" | sendmail root

Changing the hostname

# hostnamectl set-hostname server1.devopsroles.com

The setting of less command.

cat << '_EOF_' >> ~/.bashrc
export VISUAL=vim
export LESS="-M"
_EOF_

The -M option always displays the file name, number of lines, and progress.

vim command

cat << '_EOF_' >> ~/.vimrc && mkdir -p ~/.vim/tmp
set encoding=utf-8
set directory=~/.vim/tmp
set backupdir=~/.vim/tmp
set undodir=~/.vim/tmp
_EOF_

Change the location of temporary files such as .swp.

Yum plugin 

# yum -y install epel-release && yum -y yum-axelget yum-changelog yum-cron yum-plugin-ps yum-plugin-remove-with-leaves yum-plugin-rpm-warm-cache yum-plugin-show-leaves yum-utils

utility

There are many commands that are not installed in minimal.

# yum -y install bind-utils net-tools policycoreutils-python psmisc rlwrap traceroute tree vim-enhanced wget

Compression and decompression

# yum -y install epel-release && yum -y install unzip bzip2 lbzip2 pbzip2 pigz pxz

Installing the monitoring tool

Disabling GSSAPIAuthentication

Speed up SSH login by disabling GSSAPIAuthentication.

# sed -i '/GSSAPIAuthentication / s/yes/no/' /etc/ssh/sshd_config

limit of the number of old kernel packages

# sed -e '/installonly_limit/ s/5/2/' -i /etc/yum.conf

Interactive option

cat << "_EOF_" > /etc/profile.d/alias.sh
alias crontab='crontab -i'
alias cp='cp -i'
alias mv='mv -i'
alias rm='rm -i'
_EOF_

File rewrite prohibition by redirection

Edit .bashrc file

set -o noclobber

Yum Disable Excludes

# echo "exclude=kernel* centos*" >> /etc/yum.conf
# echo "alias yum='yum --disableexcludes=all'" >> /etc/profile.d/yum.sh

security settings

sed -i.org /etc/login.defs -e '/PASS_MIN_DAYS/ s/0/1/' -e '/PASS_MAX_DAYS/ s/99999/3650/'
sed -i /etc/profile -e  's/umask 002/umask 027/' -e 's/umask 022/umask 027/'

cat << "_EOF_" > /etc/modprobe.d/blacklist.conf
blacklist usb-storage
blacklist firewire_core
blacklist firewire_ohci
_EOF_

for i in $(find /lib/modules/`uname -r`/kernel/drivers/net/wireless -name "*.ko" -type f) ; do echo blacklist $i >> /etc/modprobe.d/blacklist-wireless ; done
sed -i.org 's/#AllowTcpForwarding yes/AllowTcpForwarding no/' /etc/ssh/sshd_config
sed -i 's/#ClientAliveCountMax 3/ClientAliveCountMax 2/' /etc/ssh/sshd_config
sed -i 's/#Compression delayed/Compression no/' /etc/ssh/sshd_config
sed -i 's/#LogLevel INFO/LogLevel VERBOSE/' /etc/ssh/sshd_config
sed -i 's/#MaxAuthTries 6/MaxAuthTries 2/' /etc/ssh/sshd_config
sed -i 's/#MaxSessions 10/MaxSessions 2/' /etc/ssh/sshd_config
##sed -i 's/#PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config
##sed -i 's/#Port 22/Port 10022/' /etc/ssh/sshd_config
sed -i 's/#TCPKeepAlive yes/TCPKeepAlive no/' /etc/ssh/sshd_config
sed -i 's/#UseDNS yes/UseDNS no/' /etc/ssh/sshd_config
sed -i 's/X11Forwarding yes/X11Forwarding no/' /etc/ssh/sshd_config
sed -i 's/#AllowAgentForwarding yes/AllowAgentForwarding no/' /etc/ssh/sshd_config

cat << "_EOF_" >> /etc/sysctl.conf
kernel.kptr_restrict=2
kernel.sysrq=0
net.ipv4.conf.all.accept_redirects=0
net.ipv4.conf.all.log_martians=1
net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.default.accept_redirects=0
net.ipv4.conf.default.log_martians=1
net.ipv4.tcp_timestamps=0
net.ipv6.conf.all.accept_redirects=0
net.ipv6.conf.default.accept_redirects=0
_EOF_

# sysctl -p
# chmod 700 /usr/bin/as

Fail2ban

# yum -y install epel-release && yum -y install fail2ban{,-systemd}

cat << "_EOF_" > /etc/fail2ban/jail.local
[DEFAULT]
ignoreip = 127.0.0.1/8 192.168.0.0/24
[sshd]
enabled  = true
_EOF_

# fail2ban-client -d
# systemctl start fail2ban && systemctl enable $_
# fail2ban-client status
# fail2ban-client status sshd

Conclusion

You have the initial configuration of CentOS 7. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Influxdb examples: Enhancing Your Time-Series Data Management

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Introduction

InfluxDB, a widely-used open-source time series database, excels in handling large volumes of time-stamped data for applications like monitoring systems, IoT devices, and financial tracking. This tutorial will guide you through querying InfluxDB, demonstrating practical examples and setup instructions.

If you haven’t installed InfluxDB yet, refer to the installation guide provided earlier to get started. This introduction sets the stage for you to effectively manage and analyze time-series data using InfluxDB’s powerful features.

InfluxDB examples

InfluxDB show databases

[root@MonitoringServer ~]# influx
Connected to http://localhost:8086 version 1.7.4
InfluxDB shell version: 1.7.4
Enter an InfluxQL query

> show databases                                                                                                         
name: databases
name
----
_internal
devopsrolesDB
telegraf

Use databases

> use devopsrolesDB                                                                                                              
Using database devopsrolesDB
>

Uptime Server

> select last("uptime_format") as "value" from "system" where "host" =~ /DevopsRoles\.com$/ AND time >= now() - 1h GROUP BY time(60s)

Check Root FS used

> SELECT last("used_percent") FROM "disk" WHERE ("host" =~ /^DevopsRoles\.com$/ AND "path" = '/') AND time >= now() -6h GROUP BY time(5m) fill(null)

Swap used

> SELECT last("used_percent") FROM "swap" WHERE ("host" =~ /^DevopsRoles\.com$/) AND time >= now() -1h GROUP BY time(5m) fill(null)

Users login

> SELECT last("n_users") FROM "system" WHERE ("host" =~ /^DevopsRoles\.com$/) AND time >= now() -1h GROUP BY time(5m) fill(null)

CPU usage

> SELECT last("usage_idle") * -1 + 100 FROM "cpu" WHERE ("host" =~ /^DevopsRoles\.com$/ AND "cpu" = 'cpu-total') AND time >= now() -1h GROUP BY time(5m) fill(null)

RAM Usage

> SELECT last("used_percent") FROM "mem" WHERE ("host" =~ /^DevopsRoles\.com$/) AND time >= now() -1h GROUP BY time(5m) fill(null)

CPU Load

> SELECT mean(load1) as load1,mean(load5) as load5,mean(load15) as load15  FROM "system" WHERE host =~ /^DevopsRoles\.com$/ AND time >= now() -1h GROUP BY time(5m) fill(null)

CPUs number

>  SELECT last("n_cpus") FROM "system" WHERE ("host" =~ /^DevopsRoles\.com$/) AND time >= now() -1h GROUP BY time(5m) fill(null)

Other Influxdb examples

How to list all value systems, swap, CPUs, Memory, and so on.

Enter as following for the system

> select * from "system" where host =~ /^DevopsRoles\.com$/ AND time >= now() -1h

## The output as below:
name: system
time                host                         load1 load15 load5 n_cpus n_users uptime  uptime_format
----                ----                         ----- ------ ----- ------ ------- ------  -------------
1574665340000000000 DevopsRoles.com 0.27  0.03   0.11  4      1       8105215 93 days, 19:26
1574665350000000000 DevopsRoles.com 0.22  0.03   0.1   4      1       8105225 93 days, 19:27
1574665360000000000 DevopsRoles.com 0.19  0.03   0.1   4      1       8105235 93 days, 19:27

CPU

> select * from "cpu" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:                                                                                                                                             
name: cpu
time                cpu       host                         usage_guest usage_guest_nice usage_idle        usage_iowait        usage_irq usage_nice usage_softirq        usage_steal          usage_system         usage_user
----                ---       ----                         ----------- ---------------- ----------        ------------        --------- ---------- -------------        -----------          ------------         ----------
1574670090000000000 cpu-total DevopsRoles.com 0           0                99.92494371410935 0                   0         0          0                    0                    0.025018764076678877 0.050037528153357755
1574670090000000000 cpu0      DevopsRoles.com 0           0                100               0                   0         0          0                    0                    0                    0
1574670090000000000 cpu1      DevopsRoles.com 0           0                99.89989990213955 0                   0         0          0                    0                    0.1001001000954934   0
1574670090000000000 cpu2      DevopsRoles.com 0           0                99.89979960143319 0                   0         0          0                    0                    0.10020040080409609  0
1574670090000000000 cpu3      DevopsRoles.com 0           0                100               0                   0         0          0                    0                    0                    0
1574670100000000000 cpu-total DevopsRoles.com 0           0                99.79989994515057 0.12506253122346286 0         0          0                    0                    0.05002501250212444  0.02501250625561197
1574670100000000000 cpu0      DevopsRoles.com 0           0                99.49949949205266 0.5005005005184352  0         0          0                    0                    0                    0
1574670100000000000 cpu1      DevopsRoles.com 0           0                100               0                   0         0          0                    0                    0                    0
1574670100000000000 cpu2      DevopsRoles.com 0           0                99.79999999517575 0                   0         0          0                    0                    0.09999999999286956  0.09999999998377461
1574670100000000000 cpu3      DevopsRoles.com 0           0                100               0                   0         0          0                    0                    0                    0
1574670110000000000 cpu-total DevopsRoles.com 0           0                99.64982491096929 0.22511255633968244 0         0          0                    0.025012506253392856 0.05002501250223596  0.05002501249768622

DISK

> select * from "disk" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:                                                                                                                                            
name: disk
time                device                         free        fstype host                         inodes_free inodes_total inodes_used mode path         total        used        used_percent
----                ------                         ----        ------ ----                         ----------- ------------ ----------- ---- ----         -----        ----        ------------
1574670150000000000 10.10.10.225:/mnt_nfs/data_volume/ 64795705344 nfs4   DevopsRoles.com 5924993     6553600      628607      rw   /mnt_nfs/data 105554903040 35373711360 35.313883742109724
1574670150000000000 mapper/VolGroup-lv_root        40046198784 ext4   DevopsRoles.com 3014316     3182400      168084      rw   /            51484815360  8823488512  18.0551360162319
1574670150000000000 vda1                           427900928   ext4   DevopsRoles.com 127976      128016       40          rw   /boot        507744256    53628928    11.137196859502726
1574670150000000000 vdb1                           9870200832  ext4   DevopsRoles.com 655325      655360       35          rw   /app         10568843264  161775616   1.612599639149392

Diskio

> select * from "diskio" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:              
name: diskio
time                host                         io_time   iops_in_progress name read_bytes read_time reads  weighted_io_time write_bytes write_time writes
----                ----                         -------   ---------------- ---- ---------- --------- -----  ---------------- ----------- ---------- ------
1574670240000000000 DevopsRoles.com 137167292 0                dm-0 2659918848 2451413   181804 3747940429       51691593728 3745384372 12620365
1574670240000000000 DevopsRoles.com 3102      0                vdb1 5949440    3049      770    5493             315904      2445       59
1574670240000000000 DevopsRoles.com 6376      0                dm-1 7897088    31096     1928   68191            27774976    37096      6781
1574670240000000000 DevopsRoles.com 137161235 0                vda  2674118656 1651142   137682 1886179382       51719428096 1884529301 4253428
1574670240000000000 DevopsRoles.com 667       0                vda1 2124800    370       521    667              47104       297        19
1574670240000000000 DevopsRoles.com 107       0                sr0  155648     107       49     107              0           0          0

Kernel

> select * from "kernel" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:                                                                                                                                           
name: kernel
time                boot_time  context_switches entropy_avail host                         interrupts processes_forked
----                ---------  ---------------- ------------- ----                         ---------- ----------------
1574670390000000000 1566560125 897266212        1320          DevopsRoles.com 611974729  543719
1574670400000000000 1566560125 897267347        1320          DevopsRoles.com 611975497  543719
1574670410000000000 1566560125 897268311        1320          DevopsRoles.com 611976101  543719
1574670420000000000 1566560125 897269308        1355          DevopsRoles.com 611976734  543719
1574670430000000000 1566560125 897270363        1396          DevopsRoles.com 611977420  543719
1574670440000000000 1566560125 897271391        1412          DevopsRoles.com 611978084  543719
1574670450000000000 1566560125 897272328        1412          DevopsRoles.com 611978685  543719
1574670460000000000 1566560125 897273390        1423          DevopsRoles.com 611979457  543719
>

Network

> select bytes_recv,bytes_sent,drop_in,drop_out from "net" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:                                                                                                        
name: net
time                bytes_recv  bytes_sent  drop_in drop_out
----                ----------  ----------  ------- --------
1574670830000000000 42310540034 60204453178 0       0
1574670840000000000 42310549919 60204469772 0       0
1574670850000000000 42310565133 60204488497 0       0
1574670860000000000 42310577265 60204503755 0       0
1574670870000000000 42310587249 60204520594 0       0
1574670880000000000 42310613504 60204538330 0       0

Processes

> select * from "processes" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:                                                                                                                                         
name: processes
time                blocked dead host                         idle paging running sleeping stopped total total_threads unknown zombies
----                ------- ---- ----                         ---- ------ ------- -------- ------- ----- ------------- ------- -------
1574670990000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   209           0       0
1574671000000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   209           0       0
1574671010000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   210           0       0
1574671020000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   210           0       0
1574671030000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   210           0       0
1574671040000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   210           0       0
1574671050000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   210           0       0
1574671060000000000 0       0    DevopsRoles.com 0    0      0       126      0       126   210           0       0

swap

> select * from "swap" where host =~ /^DevopsRoles\.com$/ AND time >= now() - 120s

## The output as below:                                                                                                                                              
name: swap
time                free      host                         in      out      total     used     used_percent
----                ----      ----                         --      ---      -----     ----     ------------
1574671030000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671040000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671050000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671060000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671070000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671080000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671090000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671100000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956
1574671110000000000 831287296 DevopsRoles.com 6680576 27774976 855629824 24342528 2.8449835801889956

How to show tag values.

SHOW TAG VALUES FROM system WITH KEY=host
SHOW TAG VALUES FROM "cpu" WITH KEY = "cpu" WHERE host =~ /$server/
SHOW TAG VALUES FROM "disk" WITH KEY = "device"
SHOW TAG VALUES FROM "net" WITH KEY = "interface" WHERE host =~ /$server/

Conclusion

Through the article, How to query Influxdb examples above. InfluxDB is widely used in various domains, including DevOps, IoT, monitoring and observability, and real-time analytics, due to its high performance, scalability, and ease of use. I hope will this your helpful. Thank you for reading DevOpsRoles.com page

Linux

Linux understand Page cache and buffer cache

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In this tutorial, I have written about Linux understand Page cache and buffer cache in Linux System.

Most file-system cache data read from disk.

Linux understand Page cache

What does Page cache work?

A cache of data is accessed via the file system.

How to check page cache is actually used.

Create a large file

[root@DevopsRoles ~]# mkdir /test
[root@DevopsRoles ~]# dd if=/dev/zero of=/test/large.txt count=100 bs=10M
100+0 records in
100+0 records out
1048576000 bytes (1.0 GB) copied, 1.62731 s, 644 MB/s
[root@DevopsRoles ~]# echo 3 > /proc/sys/vm/drop_caches

Check memory usage before putting it in the page cache

[root@DevopsRoles ~]# vmstat
 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  1  0      0 377344      0  64336    0    0   441  5203  131  293  0  2 97  0  0

[root@DevopsRoles ~]# cat /test/large.txt > /dev/null

Check memory usage after getting on page cache

[root@DevopsRoles ~]# vmstat 
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 2  0      0   6500      0 435008    0    0  3265  3008  108  179  0  2 98  0  0

We will confirm that accessing data in the cache is fast.

Run command 1s

[root@DevopsRoles ~]# time cat /test/large.txt > /dev/null

real	0m1.068s
user	0m0.003s
sys	0m0.987s

Run command 2s

[root@DevopsRoles ~]# time cat /test/large.txt > /dev/null

real	0m1.064s
user	0m0.003s
sys	0m0.981s

Linux understand buffer cache

What does Buffer cache work?

Cache data accessed via raw I/O. It is a page cache for block devices.

How to check Buffer cache is actually used.

[root@DevopsRoles ~]# vmstat
 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  1  0      0   5668      0 435832    0    0  6434  2087  116  132  0  2 98  0  0
 [root@DevopsRoles ~]# dd if=/dev/sda of=/dev/null count=100 bs=10M
 100+0 records in
 100+0 records out
 1048576000 bytes (1.0 GB) copied, 1.59043 s, 659 MB/s

Increase buffer cache (buff)

We will confirm that accessing data in the cache is fast.

Run command 1s

[root@DevopsRoles ~]# vmstat
 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  2  0      0  13408 359528  68520    0    0  7715  1888  123  127  0  2 98  0  0
 [root@DevopsRoles ~]# time dd if=/dev/sda of=/dev/null count=100 bs=10M
 100+0 records in
 100+0 records out
 1048576000 bytes (1.0 GB) copied, 1.13208 s, 926 MB/s
 real    0m1.138s
 user    0m0.001s
 sys    0m1.068s

Run command 2s

[root@DevopsRoles ~]# vmstat
 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  2  0      0  13664 359220  68520    0    0  8896  1747  130  119  0  2 98  0  0
 [root@DevopsRoles ~]# time dd if=/dev/sda of=/dev/null count=100 bs=10M
 100+0 records in
 100+0 records out
 1048576000 bytes (1.0 GB) copied, 1.13821 s, 921 MB/s
 real    0m1.144s
 user    0m0.001s
 sys    0m1.072s

Conclusion

Linux understand Page cache and buffer cache. I hope will this your helpful. Thank you for reading the DevopsRoles page!