Kelvin's tech-box (Page 2)

Kelvin's tech-box

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How to copy object in JavaScript

1. Clone objects When you try to use equal operator '=' to copy an object A to a variable B in JavaScript, actually you only got a reference of A to B, that means when any value changes on B will effect A, like: const A = { 'name'

webdav setup

Today I want to setup the webdav service on my self-host server to be able sync the omniFocus data among my apple devices. I've already the default installed nginx service up on the server, the webdav modules are needed, and nginx-extras package contains the mod-http-dav-ext module, $ apt install

Postgres raise `remaining connection slots are reserved for non-replication superuser connections` error

The Reporting service raised the following error today: FATAL: remaining connection slots are reserved for non-replication superuser connections I check the database activity and relevant configurations via the following commands: check current using connection number: select count(1) from pg_stat_activity; check all the connections(not include current client

Ubuntu i3 window manger + Dell docker + HDMI interface display

I have a dell XPS laptop that made in 2015, which equipped with Intel® Core™ i7-5500U CPU @ 2.40GHz × 4 and 8 G memory, and there's only one mini Display port on this machine, at that time, I also bought a dell docker which has 2 HDMI interfaces.

Postgres DB dump and restore

Export a database pg_dump -U username dbname > dbexport.pgsql pg_dump -U db_user -W -F t db_name > /path/to/your/file/dump_name.tar -F is used to specify the format of the output file, which can be one of the following: p – plain-text SQL

Securely setup Docker on linux server

This tutorial demonstrates how to setup docker by using tls certs, and the client can connect with the ssl certs securely. Install Docker sudo apt-get install apt-transport-https ca-certificates curl gnupg-agent software-properties-common curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add - sudo apt-key fingerprint 0EBFCD88 sudo add-apt-repository

Kafka introduction

Why Kafka is fast? There're some majar reasons why Kafka is much faster than most of its competitors: 1. Avoid Random Disk Access Kafka writes everything onto the disk in order and consumers fetch data in the same order too. So disk access always works sequentially instead of

How did I use LXD to manage dev environment?

I've used LXD for a while when I worked for Canonical, it's really cool thing to create the isolated linux development environments. What is LXD? The main feature of LXD is that it provides the virtual machines similar functions by using and managing the linux containers.

Kernel upgrade issue with new start udisk

Recently I upgrade my dell XPS laptop SSD to Samsung 970 EVO NVMe M.2, but because my laptop is a little old(2015 produced), it didn't fully support NVMe, once I install the Ubuntu 18.04, it can't start. After some search, I found a

My vim configuration for daily dev and writing on Ubuntu

[update 2021.3.25] In the recent typescript/javascript project, I've updated a bunch of plugins and configration to have a better experiece to read and write code. TypeScript support plugins: Please the following config into ~/.vimrc.bundle.local file: Bundle 'leafgarland/typescript-vim' " TypeScript syntax