How to Fix Cannot open your terminal ‘/dev/pts/2’ – please check

by A. J.

Normally we see a common error when we switch or sudo to a user to run the screen session and it gets closes with the error ‘Cannot open your terminal ‘/dev/pts/2′ – please check’. fix it very tiny but it took a long for me to find so I thought I will share the quick fix and save our prices time.

Error:

[thedbadmin@testdb01 ~]$ screen -x 12991.screen_testCannot open your terminal ‘/dev/pts/0’ – please check.[thedbadmin@testdb01 ~]$

Step 1: logout from the user that you have logged in.

Step 2: log as your user or from where you want to run screen and just give full privileged to /dev/pts/*

Fix : 
$ chmod 777 /dev/pts/*

Note: if you get any warning or error after executing the above command, just ignore it safely.

Now you can start the screen again hopefully you won’t see that error again

Happy programming !!!

Take MySQL backup From Jenkins Job

by A. J.

Take MySQL Database Backup From Jenkins

In this post, we will explain and practically show how you can configure MySQL database backup using Jenkins jobs. in easy words, you will automate the MySQL database backup process from Jenkins GUI and MySQL dump command. Normally we use MySQL dump from CLI or using the windows option. In this case, just automate the MySQL dump triggering from a shell script which will be called by Jenkins job with parameter. MySQL dump needs few parameters to run just pass them by build with parameter option in jenkins.

1. Log to Jenkins default URL and port: http://192.168.56.21:8080/

If you want to install and setup Jenkins see this article

2. Go to New items

3. Give some Name and select FreeStyle project

4. In the build section click on Add build step radio button and select Execute shell.

5. Select boolean parameter for MySQL database host and database superuser password which is root password in MySQL database case.

6. In this build part give the shell script name with full path and parameters like $HOST_IP & $Password

Shell Script

[root@master01 ~]# cat /opt/jenkins_scripts/mysql_full_db_backup.sh
#!/bin/bash
HOST_IP=$1
PASSWORD=$2
echo "starting mysql database full backup"
mysqldump -h $HOST_IP --all-databases --single-transaction --quick --lock-tables=false > /opt/jenkins_scripts/mysql_backup/full_backup_$(date +%F_%N).sql -u root -p$PASSWORD
echo "Backup has been done"

[su_box title=”IMP Note” box_color=”#fe2227″ title_color=”#101112″]Note: Make sure Jenkins have execute (chmod +x /opt/jenkins_scripts/mysql_full_db_backup.sh) privilege on script[/su_box]

7. Let’s execute the Jenkins job

7.1 click on the the MySQL database backup job

7.2 Click on build with Parameter

7.3 Give your database server name or IP. In my case Mysql database running on the same server that’s thy, I will give localhost and database root password

7.4 Once your job is executed go to that job open it in console output mode and check the status of the job. And you are DONE!!!

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Apache Tomcat: java.net.BindException: Permission denied (Bind failed) :443

by A. J.

How to fix error: Apache tomcat : java.net.BindException: Permission denied (Bind failed) <null>:443

Full Error:

SEVERE: Failed to initialize end point associated with ProtocolHandler ["http-bio-4443"]
java.net.BindException: Permission denied (Bind failed) <null>:4443
	at org.apache.tomcat.util.net.JIoEndpoint.bind(JIoEndpoint.java:413)
	at org.apache.tomcat.util.net.AbstractEndpoint.init(AbstractEndpoint.java:715)
	at org.apache.coyote.AbstractProtocol.init(AbstractProtocol.java:452)
	at org.apache.coyote.http11.AbstractHttp11JsseProtocol.init(AbstractHttp11JsseProtocol.java:119)
	at org.apache.catalina.connector.Connector.initInternal(Connector.java:978)
	at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
	at org.apache.catalina.core.StandardService.initInternal(StandardService.java:560)
	at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
	at org.apache.catalina.core.StandardServer.initInternal(StandardServer.java:840)
	at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
	at org.apache.catalina.startup.Catalina.load(Catalina.java:642)
	at org.apache.catalina.startup.Catalina.load(Catalina.java:667)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.startup.Bootstrap.load(Bootstrap.java:253)
	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:427)
Caused by: java.net.BindException: Permission denied (Bind failed)
	at java.net.PlainSocketImpl.socketBind(Native Method)
	at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:387)
	at java.net.ServerSocket.bind(ServerSocket.java:390)
	at java.net.ServerSocket.<init>(ServerSocket.java:252)
	at java.net.ServerSocket.<init>(ServerSocket.java:196)
	at javax.net.ssl.SSLServerSocket.<init>(SSLServerSocket.java:136)
	at sun.security.ssl.SSLServerSocketImpl.<init>(SSLServerSocketImpl.java:71)
	at sun.security.ssl.SSLServerSocketFactoryImpl.createServerSocket(SSLServerSocketFactoryImpl.java:80)
	at org.apache.tomcat.util.net.jsse.JSSESocketFactory.createSocket(JSSESocketFactory.java:256)
	at org.apache.tomcat.util.net.JIoEndpoint.bind(JIoEndpoint.java:400)
	... 17 more

Why, when, and where we get this error?

We get this issue while starting Apache tomcat on secure port 443. The error “java.net.BindException: Permission denied (Bind failed) :443 ” is visible in /usr/share/tomcat/logs/catalina.2016-12-02.log

How to fix it

This error occurs when your Linux firewall levels are set to ‘enforcing‘.To fix this error make it ‘permissive‘

Check current firewall status using the command ‘getenforce‘

Edit the file ‘vi /etc/selinux/config’ and make it ‘permissive’ from ‘enforcing’

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#       enforcing - SELinux security policy is enforced.
#       permissive - SELinux prints warnings instead of enforcing.
#       disabled - No SELinux policy is loaded.
SELINUX=permissive
# SELINUXTYPE= can take one of these two values:
#       targeted - Targeted processes are protected,
#       mls - Multi Level Security protection.
SELINUXTYPE=targeted

Reboot the system using ‘reboot‘ as the root
After reboot check, if tomcat is up with 443 port
```
netstat -plan| grep 443
```
And check the tomcat URL with ssl/https (https://localhost:443)

Leave a comment if you find the article helpful.

How to Loop in Bash | Linux /Shell Script | Automation

by A. J.

How to Loop in Bash | Linux /Shell Script | …

How to create Linux/RHEL8 machine on AWS (Amazon Web Services) using EC2 service

by A. J.

How to create Linux/RHEL8 machine on AWS (Amazon Web Services) using EC2 service

Day by day IT infrastructures is moving to cloud including compute servers, databases, network or storage. In some cases, you may see that whole infrastructure itself has provisioned on cloud or combination of in house and cloud which you can say ‘Hybrid cloud‘. It is becoming mandatory for IT professionals to obtain operational knowledge about cloud and its service providers like Amazon AWS, GCP (google cloud), Microsoft Azure, Alibaba Cloud or Oracle Cloud.

In this blog post, I am going to explain how you can create a AWS EC2 machine with Red-hat Enterprise Linux 8 using some simple steps.

Prerequisites: You should be having an active AWS account

1. Login to AWS console/account and search for EC2 service

How to fix centos full screen issue in Oracle VirtualBox

by A. J.

How to Fix CentOS Full-Screen Issue on Oracle Virtual Box

We install centos7 on top of Oracle VirtualBox and after even successful installation we don’t see the full-screen under Virtual machine the same like the following image.

This post has step by step workaround to get the full-screen Centos on the virtual box and you can also adjust the screen resolution once you are all set.