behavior will become part of you

We get what we invest in. The time we spend comes back, with interest.

If you practice five minutes of new, difficult banjo music every day, you’ll become a better banjo player. If you spend a little bit more time each day whining or feeling ashamed, that behavior will become part of you. The words you type, the people you hang with, the media you consume

The difference between who you are now and who you were five years ago is largely due to how you’ve spent your time along the way.

The habits we groove become who we are, one minute at a time.

A small thing, repeated, is not a small thing.

Why we need patching linux kernel?

• Kernel patches are released for a number of reasons, but fixing security holes is the most frequent reason. This is why it’s important to install the patch as soon as possible.
• Unlike other operating systems, Linux is able to update many different parts of the system without a reboot, but the kernel is different. Every running process integrates with the kernel intimately, so switching out parts of the kernel while it is running is quite risky. So, When the kernel is updated via a patch, the system needs to reboot

“No Reboot” Kernel patching

• On the other hand, rebooting the computer is irksome, and in some cases, where uptime is important, it can be a real issue. This is why “no reboot” kernel patching has been a priority for many administrators.
• Some servers and critical real-time applications must not be taken down without advanced scheduling, even for a few minutes. This can be a pain when administrators need to keep the system secure and a patch is released to repair a newly discovered security hole. In this case, no-reboot patching becomes a real boon
• Recognizing this need, Red Hat has been working on kpatch, and SUSE has been working on kGraft. Both of these programs are designed to accomplish the same task, but they take a different approach and have different strengths.
• But this doesn’t mean that system reboots are gone forever. Even on a system with the Linux 4.0 kernel, there will be security updates that still require a reboot, because there are other non-kernel components that can require patching, and some of these require a reboot as part of the process.

Without DNS, we would only be able to visit any website directly via IP address, no human-readable anymore

DNS: Basic concept and information

• DNS stands for Domain Name System
• Its purpose is to resolve and translate human-readable website name to IPv4 or IPv6 address
• It’s basically a large Database which resides on various servers around the world, that contains the names and IP address of various host/domains.
• Without DNS, we would only be able to visit any website directly via IP address, no human-readable anymore
• DNS works on both the TCP and UDP Protocols, port 53

How does DNS work?

Whenever you visit a domain such as github.com, the browser’s journey begins »>

Step 1: Request information

• TODO: Type github.com to address bar of Chrome, it’s a new request for browser

Step 2: DNS cache on Chrome

• TODO: DNS query on chrome’s cache, see chrome://net-internals/#dns
• True: Return IP address of this domain for making a request
• False: Didn’t know it before –> call OS (step3)

Habit

Habit: something that you do often and regularly, sometimes without knowing that you are doing it. It takes 21 days to form a new habit:

• Do it For Yourself
• Know the Benefits
• Know the Pain
• Start Simple
• Make it Daily
• Stay Consistent

Time management

Most important thing: Work more when you’re in the zone. Relax when you’re not.

• It’s normal to have days where you just can’t work, and days where you’ll work 12 hours straight.
• Stop multi-tasking. It merely kills your focus.
• We’re always more focused and productive with limited time.

Command:

mysql> FLUSH TABLES WITH READ LOCK;

What exactly does command do?

1. Set the global read lock - after this step, insert/update/delete/replace/alter statements cannot run
2. Close open tables - this step will block until all statements started previously have stopped
3. Set a flag to block commits