Kevin Jiang's Technical Blog

⚠ This article requires Rooted Android phones, please follow the instructions with caution.

Background

Since Android 5, the Android system have added the capability of multi-user, the aim is most likely to make sharing devices easier between different users in the family. Later on, Google added again something called profile, this allows enterprise to manage devices their employers use. In this article, I am going to explore some other possibilities enabled by multiuser/profile functionality. More specifically I'm going to focus on the restricted user profile.

Problem to Solve

There are several problems I'm aiming to solve with the restricted profile:

• I want to focus on things that actually matter rather than spending too much time on my phone, I would like my phone to be without any apps that can disturb or distract me when I want to focus. But I don't want to uninstall certain apps, as they are necessary in order to keep in touch with my family and friends.
• I want to install certain apps that can track me into a separate space, a space where it is impossible for them to track me using the microphone, camera, or location.
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This week I encountered some issues with Terraform (and, well, Kubernetes) again. This time, the problem was way more interesting than I thought.

Recently, I started to build an application with Go, it is a quite simple application that does something very basic and then sends an notification to a telegram bot. It's quite obvious to me this kind of application is quite suitable to run as Lambda, and that's where I decided to deploy my application to once it is working well locally. It turned out that I had to solve several issues I encountered. Here I share how I solved those issues, so you don't have to scratch your head when encounter them.

Steps:

• Download the bin file needed to upgrade the package
• Create a list of all the installed packages on current version using opkg list-installed | cut -f 1 -d ' ' > /root/installed_packages.txt
• Choose one of the following methods to flash:
  • Flash the file from the Luci interface
    OR
  • Download the file to the /tmp and then flash using sysupgrade /tmp/*.bin
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Like it or not, 2020 has been a year where video conference are used a lot. For me, most of the meetings happens in Zoom. Finding the link to the meeting in the calendar and then clicking on it to join the meeting had gradually become a new norm and something I really don't like (the fact that after clicking on the Zoom link brings up your browser instead of Zoom itself, and prompting you to click again to open Zoom is really a pain). As someone who would like to automate things as much as possible, I did eventually find a solution that works for me albeit several third party tools are required.

Problem Statement: Automatically join a Zoom call for a meeting scheduled in calendar without user interaction (on MacOS X).

Prerequisite:

• Alfred
  (Unclear if you need to be a paid user to create custom workflows, the author is a paid user)
• zoom-calendar.alfredworkflow
  (Yep, I found this alfred workflow by chance and based my work and this blog on this workflow, it is very handy and I would really like thank the author for creating this.)
• Automator
  (The builtin automation app in MacOS from Apple)
  Read more »

As a developer, you will sometimes face weird problems, it is important to come up with reliable and repeatable ways to solve this problems, so when such problems come up again, you would be able to find a solution easier. As for myself, one of the tools that I found most useful on Unix-like system is jq, which is a tool to process json files. Let me demonstrate how I use this tool to solve some problems I encountered during work.

What would be the easiest way to remove all but one word from the end of each line in Vim?

Today, I found a challenge on vimgolf and thought it might be interesting to share my solutions.

Here is the original file

1
2
3
4

abcd 1 erfg 7721231
acd 2 erfgasd 324321
acd 3 erfgsdasd 23432
abcd 5 erfgdsad 123556

Here is the desired result:

1
2
3
4

7721231
324321
23432
123556

The challenge is quite straightforward, delete all but the last characters in the file. I found several ways to tackle this challenge, so let me show you all:

This week, I was tasked with creating basic infrastructure for one of our newwebsites. We use Fastly for our CDN and New Relic as a log aggregation tool, most of our infrastructure is setup using Terraform, which is a popular infrastructure as code (IaC) platform. Terraform supports Fastly through a custom plugin, which also has the capability of New Relic. We need to customize the format of New Relic so that we can find the logs easily in New Relic. As expected, the plugin actually provide a pretty straight forward to accomplish this -- what you need to do is to come up with a proper json string that align with the format that Fastly provided in their document. This seemingly straightforward task ended up took me some time to debug.

Recently, I have been eager to get the data saver on Android to work automatically for me. My goal is to have Tasker automatically enable the built-in data saver when my data is low. Before I came up with this idea, I have search the web to see if there is any solutions exist already so I don't have to reinventing the wheel. Unfortunately, I couldn't find anything on this topic so I have to create my own solution. Upon 1 week of testing, things to work as I expected so I decided to share in this article how I did it.

Prerequisite

• An rooted Android phone -- Unfortunately, the solution I came up with only works on rooted Android phone, I'm running Android 9.0.
• A way to get to know you current data usage -- Some carriers allow you to get you data usage through SMS, some might only allow you to use USSD to get data usage. I am only covering the case of using SMS here (my case).
  Read more »

Recently, I decided to convert my QEMU based virtual machine installed on my Manjaro Linux to the VirtualBox format. The reason behind this is that I would like to be able to use the same VM across different host system (specifically Manjaro Linux and Windows 7). It is not a easy thing to do, so I decided to document it for future references.

Prerequisite?

• An existing image created using QEMU (My VM file end with .img, for example)
• VirtualBox
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