How to Upgrade Ubuntu 16.04 to Ubuntu 18.04

 

 

sudo apt-get update -y
sudo apt-get upgrade -y
sudo apt-get dist-upgrade -y

sudo apt install update-manager-core -y

sudo do-release-upgrade

 

How to Setup MariaDB Master and Slave Replication on Ubuntu 16.04

Ref: https://alibaba-cloud.medium.com/how-to-setup-mariadb-master-and-slave-replication-on-ubuntu-16-04-850c155c5481

MariaDB is a free, open source and one of the most popular open source relational database management system. It is a drop-in replacement for MySQL intended to remain free under the GNU GPL. You will need to increase the instances of your MariaDB server and replicate the data on multiple servers when your traffic grows. The Master-Slave replication provides load balancing for the databases. It is not used for any failover solution.

There are two ways to replicate data:

Master-Master Replication: In this mode, data to be copied from either server. In other words, perform reads or writes from either server. So whenever one server gets the write request it will sync data to other server. This mode will be very useful when you want the best redundancy.

Master-Slave Replication: In this mode, data changes happen on the master server, while the slave server automatically replicates the changes from the master server. This mode will be best suited for data backups.

In this tutorial, we will learn how to set up MariaDB Master-Slave replication on Alibaba Cloud Elastic Compute Service (ECS) with Ubuntu 16.04.

Requirements

1. Two fresh Alibaba Cloud instance with Ubuntu 16.04 installed.
2. A static IP address 192.168.0.101 is configured on the Master node and 192.168.0.102 is configured on the Slave node.
3. A Root password is set up on both instance.

Launch Alibaba Cloud ECS Instance

First, log in to your Alibaba Cloud ECS Console. Create a new ECS instance, choosing Ubuntu 16.04 as the operating system with at least 2GB RAM. Connect to your ECS instance and log in as the root user.

Once you are logged into your Ubuntu 16.04 instance, run the following command to update your base system with the latest available packages.

apt-get update -y

Install MariaDB

Before starting, you will need to install MariaDB server on both instance. You can install it by running the following command:

apt-get install mariadb-server -y

Once the installation is completed, start MariaDB service and enable it to start on boot time with the following command:

systemctl start mysql
systemctl enable mysql

By default, MariaDB is not secured. So you will need to secure it first. You can do this by running the following command:

mysql_secure_installation

Answer all the questions as shown below:

Set root password? [Y/n] n
Remove anonymous users? [Y/n] y
Disallow root login remotely? [Y/n] y
Remove test database and access to it? [Y/n] y
Reload privilege tables now? [Y/n] y

Configure Master Node

First, you will need to edit /etc/mysql/my.cnf and make some changes inside it.

nano /etc/mysql/my.cnf

Make the following changes:

[mysqld]
bind-address = 192.168.0.101
server_id=1
log-basename=master
log-bin=/var/log/mysql/mariadb-bin
binlog-format=row
binlog-do-db=masterdb

Save and close the file, when you are finished.

Next, restart MariaDB service to apply the chnages:

systemctl restart mysql

Next, log in to MariaDB shell and configure replication:

mysql -u root -p

Enter your root password, then stop the slave and create a replication user and set password:

MariaDB [(none)]> STOP SLAVE;
MariaDB [(none)]> GRANT REPLICATION SLAVE ON *.* TO 'slave_user'@'%' IDENTIFIED BY 'password';

Next, flush the privileges:

MariaDB [(none)]> FLUSH PRIVILEGES;
MariaDB [(none)]> FLUSH TABLES WITH READ LOCK;

Next, check the master server status:

MariaDB [(none)]> SHOW MASTER STATUS;

Output:

+--------------------+----------+--------------+------------------+
| File               | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------------+----------+--------------+------------------+
| mariadb-bin.000001 |      615 | masterdb     |                  |
+--------------------+----------+--------------+------------------+
1 row in set (0.00 sec)

Note: Remember the file mariadb-bin.000001 and position number 615.

Next, exit from the MariaDB shell:

MariaDB [(none)]> exit;

Next, take a backup of all databases on the master server and transfer it to the slave server.

First, take all database backup with the following command:

mysqldump --all-databases --user=root --password --master-data > alldatabase.sql

Next, transfer alldatabase.sql file to the slave server with the following command:

scp alldatabase.sql root@192.168.0.102:/root/

Next, log in to MariaDB console again and unlock the tables:

mysql -u root -pMariaDB [(none)]> UNLOCK TABLES; 
MariaDB [(none)]> exit;

Configure Slave Server

You will also need to edit /etc/mysql/my.cnf file and make some changes inside it:

nano /etc/mysql/my.cnf

Make the following changes:

[mysqld]
bind-address = 192.168.0.102
server-id = 2
replicate-do-db=masterdb

Save the file, then restart MariaDB service:

systemctl restart mysql

Next, import the alldatabase.sql which you have transferred from master server:

mysql -u root -p < alldatabase.sql

Next, log in to MariaDB shell:

mysql -u root -p

Enter your root password, then stop the slave:

MariaDB [(none)]> STOP SLAVE;

Next, configure the slave to use the master with the following command:

MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.0.101', MASTER_USER='slave_user', MASTER_PASSWORD='password', MASTER_LOG_FILE='mariadb-bin.000001', MASTER_LOG_POS=615;

Next, start the slave and check slave status:

MariaDB [(none)]> START SLAVE;
MariaDB [(none)]> SHOW SLAVE STATUS\G;

Output:

*************************** 1. row ***************************
               Slave_IO_State: Connecting to master
                  Master_Host: 172.20.10.6
                  Master_User: slave_user
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mariadb-bin.000001
          Read_Master_Log_Pos: 615
               Relay_Log_File: mysqld-relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: mariadb-bin.000001
             Slave_IO_Running: Connecting
            Slave_SQL_Running: Yes
              Replicate_Do_DB: masterdb

Test Replication

Both MariaDB master and slave server are now configured. It’s time to test replication.

Navigate to the Master server, and log in to MariaDB shell:

mysql -u root -p

Enter your root password, then create a database masterdb which you have specified in my.cnf file:

MariaDB [(none)]> create database masterdb;

Next, add some tables and entries on it:

MariaDB [(none)]> use masterdb;
MariaDB [masterdb]> create table mastertable (c int);
MariaDB [masterdb]> insert into mastertable (c) values (1);

Now, check the mastertable:

MariaDB [masterdb]> select * from mastertable;

Output:

+------+
| c    |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

Now, navigate to the slave server and verify whether the above created table has been replicated:

First, log in to MariaDB shell:

mysql -u root -p

Enter your root password, then change the database to masterdb:

MariaDB [(none)]> use masterdb;

Next, check the mastertable:

MariaDB [masterdb]> select * from mastertable;

Output:

+------+
| c    |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

You should see that the database and table are replicated successfully from the master server to the slave server.

 

Install letsencrypt cer to trust CA in ubuntu

Install ca-certificates

sudo apt-get install ca-certificates

Down load cer from letsencrypt

cd /usr/share/ca-certificates

sudo wget https://letsencrypt.org/certs/isrgrootx1.pem  -O isrgrootx1.crt

sudo wget https://letsencrypt.org/certs/letsencryptauthorityx3.pem  -O letsencryptauthorityx3.crt

Update CA

sudo dpkg-reconfigure ca-certificates

How To Install Apache Tomcat 8 on Ubuntu 16.04

Introduction

Apache Tomcat is a web server and servlet container that is used to serve Java applications. Tomcat is an open source implementation of the Java Servlet and JavaServer Pages technologies, released by the Apache Software Foundation. This tutorial covers the basic installation and some configuration of the latest release of Tomcat 8 on your Ubuntu 16.04 server.

Prerequisites

Before you begin with this guide, you should have a non-root user with sudo privileges set up on your server. 

Step 1: Install Java

Tomcat requires Java to be installed on the server so that any Java web application code can be executed. We can satisfy that requirement by installing OpenJDK with apt-get.

First, update your apt-get package index:

sudo apt-get update

Then install the Java Development Kit package with apt-get:

sudo apt-get install default-jdk

Now that Java is installed, we can create a tomcat user, which will be used to run the Tomcat service.

Step 2: Create Tomcat User

For security purposes, Tomcat should be run as an unprivileged user (i.e. not root). We will create a new user and group that will run the Tomcat service.

First, create a new tomcat group:

sudo groupadd tomcat

Next, create a new tomcat user. We’ll make this user a member of the tomcat group, with a home directory of /opt/tomcat (where we will install Tomcat), and with a shell of /bin/false (so nobody can log into the account):

sudo useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat

Now that our tomcat user is set up, let’s download and install Tomcat.

Step 3: Install Tomcat

The best way to install Tomcat 8 is to download the latest binary release then configure it manually.

Find the latest version of Tomcat 8 at the Tomcat 8 Downloads page. At the time of writing, the latest version is 8.5.5, but you should use a later stable version if it is available. Under the Binary Distributions section, then under the Core list, copy the link to the “tar.gz”.

Next, change to the /tmp directory on your server. This is a good directory to download ephemeral items, like the Tomcat tarball, which we won’t need after extracting the Tomcat contents:

cd /tmp

Use curl to download the link that you copied from the Tomcat website:

curl -O http://apache.mirrors.ionfish.org/tomcat/tomcat-8/v8.5.5/bin/apache-tomcat-8.5.5.tar.gz

We will install Tomcat to the /opt/tomcat directory. Create the directory, then extract the archive to it with these commands:

sudo mkdir /opt/tomcat

sudo tar xzvf apache-tomcat-8*tar.gz -C /opt/tomcat --strip-components=1

Next, we can set up the proper user permissions for our installation.

Step 4: Update Permissions

The tomcat user that we set up needs to have access to the Tomcat installation. We’ll set that up now.

Change to the directory where we unpacked the Tomcat installation:

cd /opt/tomcat

Give the tomcat group ownership over the entire installation directory:

sudo chgrp -R tomcat /opt/tomcat

Next, give the tomcat group read access to the conf directory and all of its contents, and execute access to the directory itself:

sudo chmod -R g+r conf

sudo chmod g+x conf

Make the tomcat user the owner of the webapps, work, temp, and logs directories:

sudo chown -R tomcat webapps/ work/ temp/ logs/

Now that the proper permissions are set up, we can create a systemd service file to manage the Tomcat process.

Step 5: Create a systemd Service File

We want to be able to run Tomcat as a service, so we will set up systemd service file.

Tomcat needs to know where Java is installed. This path is commonly referred to as “JAVA_HOME”. The easiest way to look up that location is by running this command:

sudo update-java-alternatives -l

Output
java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64

The correct JAVA_HOME variable can be constructed by taking the output from the last column (highlighted in red) and appending /jre to the end. Given the example above, the correct JAVA_HOME for this server would be:

JAVA_HOME
/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre

Your JAVA_HOME may be different.

With this piece of information, we can create the systemd service file. Open a file called tomcat.service in the /etc/systemd/system directory by typing:

sudo nano /etc/systemd/system/tomcat.service

Paste the following contents into your service file. Modify the value of JAVA_HOME if necessary to match the value you found on your system. You may also want to modify the memory allocation settings that are specified in CATALINA_OPTS:

/etc/systemd/system/tomcat.service

[Unit]
Description=Apache Tomcat Web Application Container
After=network.target

[Service]
Type=forking

Environment=JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre
Environment=CATALINA_PID=/opt/tomcat/temp/tomcat.pid
Environment=CATALINA_HOME=/opt/tomcat
Environment=CATALINA_BASE=/opt/tomcat
Environment='CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC'
Environment='JAVA_OPTS=-Djava.awt.headless=true -Djava.security.egd=file:/dev/./urandom'

ExecStart=/opt/tomcat/bin/startup.sh
ExecStop=/opt/tomcat/bin/shutdown.sh

User=tomcat
Group=tomcat
UMask=0007
RestartSec=10
Restart=always

[Install]
WantedBy=multi-user.target

When you are finished, save and close the file.

Next, reload the systemd daemon so that it knows about our service file:

sudo systemctl daemon-reload

Start the Tomcat service by typing:

sudo systemctl start tomcat

Double check that it started without errors by typing:

sudo systemctl status tomcat

Step 6: Adjust the Firewall and Test the Tomcat Server

Now that the Tomcat service is started, we can test to make sure the default page is available.

Before we do that, we need to adjust the firewall to allow our requests to get to the service. If you followed the prerequisites, you will have a ufw firewall enabled currently.

Tomcat uses port 8080 to accept conventional requests. Allow traffic to that port by typing:

sudo ufw allow 8080

With the firewall modified, you can access the default splash page by going to your domain or IP address followed by :8080 in a web browser:

Open in web browser
http://server_domain_or_IP:8080

You will see the default Tomcat splash page, in addition to other information. However, if you click the links for the Manager App, for instance, you will be denied access. We can configure that access next.

If you were able to successfully accessed Tomcat, now is a good time to enable the service file so that Tomcat automatically starts at boot:

sudo systemctl enable tomcat

Step 7: Configure Tomcat Web Management Interface

In order to use the manager web app that comes with Tomcat, we must add a login to our Tomcat server. We will do this by editing the tomcat-users.xml file:

sudo nano /opt/tomcat/conf/tomcat-users.xml

You will want to add a user who can access the manager-gui and admin-gui (web apps that come with Tomcat). You can do so by defining a user, similar to the example below, between the tomcat-users tags. Be sure to change the username and password to something secure:

tomcat-users.xml — Admin User

<tomcat-users . . .>
    <user username="admin" password="password" roles="manager-gui,admin-gui"/>
</tomcat-users>

Save and close the file when you are finished.

By default, newer versions of Tomcat restrict access to the Manager and Host Manager apps to connections coming from the server itself. Since we are installing on a remote machine, you will probably want to remove or alter this restriction. To change the IP address restrictions on these, open the appropriate context.xml files.

For the Manager app, type:

sudo nano /opt/tomcat/webapps/manager/META-INF/context.xml

For the Host Manager app, type:

sudo nano /opt/tomcat/webapps/host-manager/META-INF/context.xml

Inside, comment out the IP address restriction to allow connections from anywhere. Alternatively, if you would like to allow access only to connections coming from your own IP address, you can add your public IP address to the list:

context.xml files for Tomcat webapps

<Context antiResourceLocking="false" privileged="true" >
  <!--<Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />-->
</Context>

Save and close the files when you are finished.

To put our changes into effect, restart the Tomcat service:

sudo systemctl restart tomcat