Add DR Manual

Author: yuuzukatsu

Disaster Recovery.md

@@ -0,0 +1,81 @@
+# Disaster Recovery Manual
+
+In an event/disaster where Master Database Server can't be accessed, down, or deleted we need to promote a Slave Server into a Master Server to minimize down time
+
+## Step 1
+SSH into one of your Slave Server you want to promote into Master Server 
+```
+ssh ubuntu@slave-server-ip
+```
+
+## Step 2
+Login into MySQL
+```
+sudo mysql -u root
+```
+
+If you configure root with password, enter this instead
+```
+sudo mysql -u root -p
+```
+
+## Step 3
+Stop and reset slave replication
+```
+stop slave;
+reset slave;
+```
+
+## Step 4
+By default, slave server still can write. But if you configure read only on slave server, enable write on server by adding/editing this line on `/etc/mysql/my.cnf`
+```
+[mysqld]
+read-only = 0
+```
+
+Or run this query on mysql
+```
+SET read_only false;
+```
+
+Your new master server is now ready
+
+## Step 5(and so on is optional)
+If you have other slave server, you can point them to your new master server
+In your new Master Server, run this
+
+```
+SHOW MASTER STATUS;
+```
+
+You will get something like this
+```
++------------------+----------+--------------+------------------+
+| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
++------------------+----------+--------------+------------------+
+| mysql-bin.000001 |      786 |              |                  |
++------------------+----------+--------------+------------------+
+```
+Note down the `File`, `Position`, and your server IP
+
+## Step 6
+
+SSH into your other Slave Server
+```
+ssh ubuntu@other-slave-server-ip
+```
+
+## Step 7
+Stop and reset slave replication
+```
+stop slave;
+reset slave;
+```
+
+## Step 8
+Run this query, change the variable into what you note before
+```
+CHANGE MASTER TO MASTER_HOST = '<your new master server ip>', MASTER_USER = '<replication user>', MASTER_PASSWORD = '<replication password>', MASTER_LOG_FILE = '<your master log file>', MASTER_LOG_POS = <your master log position>;
+```
+
+Repeat step 6 - 8 for each of your slave server