Containers vs Virtual Machine vs Docker

Container

Using containers, everything required to make a piece of software run is packaged into isolated containers. Unlike VMs, containers do not bundle a full operating system - only libraries and settings required to make the software work are needed. This makes for efficient, lightweight, self-contained systems and guarantees that software will always run the same, regardless of where it’s deployed. Docker is an example of container technology, there are many other likes containerd, CRI-O etc

Virtual Machine(VM'S)

Virtual machines (VMs) are an abstraction of physical hardware turning one server into many servers. The hypervisor allows multiple VMs to run on a single machine. Each VM includes a full copy of an operating system, one or more apps, necessary binaries and libraries - taking up tens of GBs. VMs can also be slow to boot.

Containers vs Virtual Machines

Containers and virtual machines have similar resource isolation and allocation benefits, but function differently because containers virtualize the operating system instead of hardware, containers are more portable and efficient

Docker

Docker is the world's leading software containerization platform, there are many other  Docker’s website describes it as “an open-source engine that automates the deployment of any application as a lightweight, portable, self-sufficient container that will run virtually anywhere.”.

• Docker is built on top of LXC, and therefore runs containers, not VMs as VirtualBox for instance 
• Docker containers are made of portable “images”, similar to LXC/VZ templates, but much more powerful (versionning, inheritance …) 
• Docker “images” can easily be created via Dockerfile’s, where are set the base image and the steps to run in order to create your image 
• Docker allows to have run multiple instances of your container without needing to copy the image (base system) files 
• Docker daemon (which manages / runs LXC containers) provides a REST API used by Docker CLI utility … but this REST API can be used by any application 
• Docker runs on virtually all operating systems (Linux, Mac OS, Windows …) and platforms (Google Cloud Platform, Amazon EC2) 

Docker is the world's leading software containerization platform.

Changing MySQL Data Disk/Directory on Linux

First stop Mysql service

/etc/init.d/mysqld stop
rename the mysql directory
mv /var/lib/mysql /var/lib/mysql_old

Mount a secondary disk as data disk, I have mounted /disk2 to my /dev/sdb

create a folder ‘mysql’ in destination disk/partition

copy whole Mysql data directory to ‘mysql’ in preserve mode

cp –pr /var/lib/mysql/ /disk2/mysql

-p means preserve the specified attributes (default: mode, ownership, timestamps)


then create a symbolic link from new data directory to old data directory

ln -s /disk2/mysql/ /var/lib/mysql/

Change permissions on /var/lib/mysql.

chown -R mysql:mysql /var/lib/mysql

If AppArmor is not enabled you do not need to do below. But it is recommended to have AppArmor enabled for security. Follow below steps to allow mysql access through AppArmor:

vim /etc/apparmor.d/usr.sbin.mysqld and add the data directory to it
/disk2/database/mysql/** rwk,
 /disk2/database/mysql/ r,

Now start Mysql service
/etc/init.d/mysqld start
If its working properly then delete each file and folder from old data directory

cd /var/lib/mysql_old rm –rf  *

NOTE: Please take a backup of your MySQL databases before attempting migration.

How to Redirect HTTP to HTTPS in Apache

Apache’s mod_rewrite makes it easy to require SSL to be used on your site and to gently redirect users who forget to add the https when typing the URL. Using Apache to redirect http to https will make sure that your site (or a part of it) will only be accessed by your customers using SSL.  This is better than using SSLRequireSSL because users often forget to type in the https and will be automatically redirected.

Before you can set up an Apache redirect from http to https, you will need to do the following:

Make sure your SSL certificate is successfully installed so you can access https://www.yoursite.com (for more information see our Apache SSL Installation instructions)
Make sure mod_rewrite is enabled in Apache
Now you just need to edit your httpd.conf file or the file where your virtual host is specified and add these lines to redirect http to https:

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

In many cases, you can also just add those lines to a file named .htaccess in the folder that you want to redirect http to https.

Now, when a visitor types http://www.yoursite.com/mypage.htm the server will automatically redirect http to https so that they go to https://www.yoursite.com/mypage.htm

Note: You can also redirect a single page from http to http in Apache by using this in your configuration file or .htaccess file:

RewriteEngine On
RewriteRule ^apache-redirect-http-to-https\.html$ https://www.yoursite.com/apache-redirect-http-to-https.html [R=301,L]

Run sudo a2enmod rewrite to enable it. Restart apache using sudo service apache2 restart and provided your .htaccess syntax is correct this will work.

https://www.sslshopper.com/apache-redirect-http-to-https.html

Slow query logs in AWS MySQL RDS

The MySQL slow query log and the general log can be written to a file or a database table by setting parameters in your DB parameter group. You must set these parameters before you can view the slow query log or general log in the Amazon RDS console or by using the Amazon RDS API, Amazon RDS CLI, or AWS SDKs.

You can control MySQL logging by using the parameters in this list:

slow_query_log: To create the slow query log, set to 1. The default is 0.
general_log: To create the general log, set to 1. The default is 0.
long_query_time: To prevent fast-running queries from being logged in the slow query log, specify a value for the shortest query execution time to be logged, in seconds. The default is 10 seconds, the minimum is 0. If log_output = FILE, you can specify a floating point value that goes to microsecond resolution. If log_output = TABLE, you must specify an integer value with second resolution. Only queries whose execution time exceeds the long_query_time value are logged. For example, setting long_query_time to 0.1 prevents any query that runs for less than 100 milliseconds from being logged.
log_queries_not_using_indexes: To log all queries that do not use an index to the slow query log, set to 1. The default is 0. Queries that do not use an index are logged even if their execution time is less than the value of the long_query_time parameter.

log_output option: You can specify one of the following options for the log_outputparameter.

TABLE (default)– Write general queries to the mysql.general_log table, and slow queries to the mysql.slow_log table.
FILE– Write both general and slow query logs to the file system. Log files are rotated hourly.
NONE– Disable logging.

When logging is enabled, Amazon RDS rotates table logs or deletes log files at regular intervals. This measure is a precaution to reduce the possibility of a large log file either blocking database use or affecting performance. FILE and TABLE logging approach rotation and deletion as follows:

When FILE logging is enabled, log files are examined every hour and log files older than 24 hours are deleted. If the remaining combined log file size after the deletion exceeds a threshold of 2 percent of a DB instance's allocated space, then the largest log files are deleted until the log file size no longer exceeds the threshold.

When TABLE logging is enabled, log tables are rotated every 24 hours if the space used by the table logs is more than 20 percent of the allocated storage space or the size of all logs combined is greater than 10 GB. If the amount of space used for a DB instance is greater than 90 percent of the DB instance's allocated storage space, then the thresholds for log rotation are reduced. Log tables are then rotated if the space used by the table logs is more than 10 percent of the allocated storage space or the size of all logs combined is greater than 5 GB. You can subscribe to the low_free_storage event to be notified when log tables are rotated to free up space.

When log tables are rotated, the current log table is copied to a backup log table and the entries in the current log table are removed. If the backup log table already exists, then it is deleted before the current log table is copied to the backup. You can query the backup log table if needed. The backup log table for the mysql.general_log table is namedmysql.general_log_backup. The backup log table for the mysql.slow_log table is named mysql.slow_log_backup.

You can rotate the mysql.general_log table by calling the mysql.rds_rotate_general_log procedure. You can rotate the mysql.slow_logtable by calling the mysql.rds_rotate_slow_log procedure.

Table logs are rotated during a database version upgrade.

* from AWS Documents