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MySQL Slave Status | master and slave have equal MySQL server UUIDs

 Master Slave Replication: After configuring master slave replication when you check slave status on slave you got Fatal error: The slave I/O thread stops because master and slave have equal MySQL server UUIDs; these UUIDs must be different for replication to work. Cause: Because you might have copied data directory from master to slave, and same auto.cnf file exists on master and slave.  Solution: Stop mysql daemon on slave, remove auto.cnf file from data directory on slave , start slave, and check slave status. You will be fine.  Stop MySQL daemon on slave: #systemctl stop mysqld Delete auto.cnf file from the data directory: # rm -rf auto.cnf Start MySQL daemon: #systemctl start mysqld 
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DC/OS prodcution installation troubleshoot | Failed to start Exhibitor

DC/OS production installation troubleshoot | Failed to start Exhibitor: Before starting production installation of the DC/OS pay attention to following. Ref.: https://docs.d2iq.com/mesosphere/dcos/2.0/installing/production/deploying-dcos/installation/#create-an-ip-detection-script Also make sure to check the Troubleshooting Guide By D2iQ In between if you realize you loose the track and you want to start from scratch, feel free to uninstall everything using Uninstalling DC/OS Following DC/OS production troubleshooting phase is available only after execution of dcos_install.sh to troubleshoot each node individually such as master, slave / agent. List DC/OS components: # sudo systemctl list-units --no-legend --no-pager --plain 'dcos-*' | awk '{print $1}'  dcos-adminrouter.service dcos-bouncer-migrate-users.service dcos-bouncer.service dcos-checks-api.service dcos-checks-poststart.service dcos-cockroach.service dcos-cockroachdb-config-change.service dcos-cosm...
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Remove Red Hat Enterprise Linux Test Page

Remove Red Hat Enterprise Linux Test Page: The purpose to stop Red Hat Enterprise Linux Page could be free port 80 for nginx web server. Explore Test Page Source: Red hat Linux Test Page - To prevent this page from ever being used, follow the instructions in the file /etc/httpd/conf.d/welcome.conf. Content of file /etc/httpd/conf.d/welcome.conf: # # This configuration file enables the default "Welcome" page if there # is no default index page present for the root URL.  To disable the # Welcome page, comment out all the lines below. # # NOTE: if this file is removed, it will be restored on upgrades. # <LocationMatch "^/+$">     Options -Indexes ErrorDocument 403 /.noindex.html </LocationMatch> <Directory /usr/share/httpd/noindex>     AllowOverride None     Require all granted  </Directory>  Alias /.noindex.html /usr/share/httpd/noindex/index.html Steps to stops Red Hat Enterprise Linux Test Page: ...
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Docker daliy command

Docker daily command: Docker Help: To get help on a topic in Docker, you can use #docker topicName --help Docker Note: Application running in a VM is hidden from the host OS with the help of Hypervisor/ VMM . Container can alter host filesystem without any restriction. Docker Information: #docker version #docker info Docker Images: #docker pull <image_name> #docker history <image_name> #docker history mysql/mysql-server:8.0.18 #docker search mysql --no-trunc List images: #docker images -a Remove images: #docker rmi <image_id | image_name> #docker rmi -f <image_id | image_name> Purging All: #docker system prune -a #docker system prune Docker daemon start  | stop | pause: #systemctl start / stop/ status docker #service docker start / stop/ status Docker for MySQL:   Note: Get tag information for Docker for MySQL from - https://hub.docker.com/_/mysql Community Edition: #docker pull mysql/mysql_server:<tag_name OR tag no.> MySQL Docker Enterprise...
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Mesos | Master | Agent | Zookeeper | Installation and Troubleshoot for Cent OS

Get RPM from the Mesosphere site: Get URL for repository from - Mesosphere Package Repositories Download MESOS version specific rpm from - https://open.mesosphere.com/downloads/mesos/#apache-mesos-1.9.0 Install MESOS fo RHEL / Cent OS: Add the repository for MESOSPHERE: # rpm -Uvh http://repos.mesosphere.com/el/7/noarch/RPMS/mesosphere-el-repo-7-3.noarch.rpm It will install most recent package of MESOSPHERE, which can install mesosphere (master and agent), marathon, and zookeeper. Install mesosphere: # yum install --enablerepo=mesosphere mesos Check mesos installation: # yum list installed | grep mesos mesos.x86_64 1.9.0-2.0.1.el7 @mesosphere mesosphere-el-repo.noarch 7-3 installed Install marathon: # yum install --enablerepo=mesosphere marathon Check marathon installation: # yum list installed | grep marathon marathon.noarch 1.9.109-1.el7 @mesosphere-noarch Install zookeeper: # yum install mesosphere-zookeeper Check zookeeper installation: # yum list installed | grep zoo* mes...
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MySQL host is blocked because of many connection errors

MySQL host is blocked because of many connection errors: This error can happen in MySQL database environment with InnoDB cluster and standalone environment. Fix for error Host .... is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts' 01. Connect mysql server:  02. Execute mysql> flush hosts   Flush hosts: Purpose of  command "flush hosts" is to empty the host cache and performance schema host_chace table, and unblocks any blocked hosts. If you have change the IP address of the host, then also you need to execute "flush hosts" to empties cache. Why it happen: Many connection errors happened when "more than max_connect_errors errors occur successively for a given host connecting to the MySQL server, MySQL assumes that something is wrong and blocks the host from further connection requests. Ref. https://dev.mysql.com/doc/refman/8.0/en/flush.html#flush-hosts How to avoid: "Flush hosts" commnad will solve...
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