Kevin Liu's Blog || Technical || Travel

What is a Job? A Job is a remote operation that is sent to and executed on one or more devices connected to AWS IoT. For example, you can define a Job that instructs a set of devices to download and install application or firmware updates, reboot, rotate certificates, or perform remote troubleshooting operations. How to create a Job?You must create a job document first. The Job Document is a description of the remote operations to be performed a Job Target When you create a Job, you specif...

PID 0 An Idle Process used to swap all pages of processs to/from memory/backing store. “Swap Process” It was there, so Linux always have CPU to execute something If you try to execute ps command on the clean Ubuntu Linux, you’ll find there was no process with “PID0” Idle systemcall not supported since kernal 2.3.13 Then how can we prove that PID0 really exist? Demo Using bpftrace for tracking the kernel function hrtimer_wakeup hrtimer_wakeup mean to: Waking up processes Move the...

AWS FreeRTOS FreeRTOS includes libraries for connectivity, security, and over-the-air (OTA) updates. FreeRTOS also includes demo applications that show FreeRTOS features on qualified boards. FreeRTOS is an open-source project. You can download the source code, contribute changes or enhancements, or report issues on the GitHub site at https://github.com/FreeRTOS/FreeRTOS. FreeRTOS - ArchitectureFreeRTOS contains two types of repositories single library repositories Each single library repo...

IntroductionWhat is Fleet Provisioning?Fleet Provisioning can be divided into Provisioning by Claim and Provisioning by Trusted User. Provisioning by ClaimDevices can use embedded provisioning claim certificates (special-purpose certificates) and private keys for manufacturing. If these certificates are registered with AWS IoT, the service can exchange them for a unique device certificate that the device can use for general operations. Provisioning by Trusted UserIn many cases, when trusted u...

Intro - What is AWS IoT Device Shadow?In real world, sometime it is difficult to get the actual device state in real time in such IoT scenarios. A device shadow can overcome this challenge, Device Shadow can consider a virtual virtual representation of a device which managed by the IoT Things resource created in AWS IoT Core. The Shadow document is a JSON or a JavaScript notation doc that is used to store and retrieve the current state information for a device. You can use the shadow to get...

IntroductionAmazon SNS offen works well with Amazon SQS, by subscribing SQS to SNS, the SNS service can push messages to SQS. This may eliminating the need to periodically check or “poll” for updates. What is Amazon SQS?By official definition Amazon SQS is a message queue service used by distributed applications to exchange messages through a polling model, and can be used to decouple sending and receiving components—without requiring each component to be concurrently available. Scenario T...

What is S3 Gateway Endpoints? Let’s consider a scenario How could your Lambda function access the content in the S3 bucket? If you want a service to access the content in the S3 bucket, it usually go through VPC endpoint. S3 supports two types of VPC endpoint,each of which is Gateway endpoint and Interface endpoint The diffeences between two types of VPC endpoints are listed below S3 Gateway Endpoints S3 Interface Endpoints Use S3 Public IP Address Use Private IP Address in VPC to a...

IntroductionBuffer Overflow Vulnerability is one of the most common and severe security vulnerabilities in the field of software and system security. In the complex software systems of today’s digital age, the threat from hackers or malicious users is ever-present. Buffer Overflow Vulnerability is one of the most concerning threats among them due to the significant threat it poses to computer systems. In simple terms, a buffer overflow vulnerability occurs when code attempts to store data in ...