huynhbaoan

## Clone a running OS from SD card to USD SSD, Raspberry 4B 8G

### Main guide
https://medium.com/xster-tech/move-your-existing-raspberry-pi-4-ubuntu-install-from-sd-card-to-usb-ssd-52e99723f07b

### References:
https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#raspberry-pi-boot-modes
https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#raspberry-pi-4-boot-flow
https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#raspberry-pi-4-boot-eeprom

huynhbaoan

# Generate du command to check disk
# Ignore all the mount points nfs4. Modify the "df -t nfs4" as you want
# Run with lowest CPU priority and lowest diskio priority

# extract the content from the last column and store it in an array
IFS=$'\n' read -d '' -ra MOUNT_POINTS <<< "$(df -h -t nfs4 | awk '{print $NF}')"

# construct the new du command with the excluded mount points
DU_COMMAND="nice -n 19 ionice -c 3 du -shxc /* --exclude=/proc"
for mount_point in "${MOUNT_POINTS[@]}"; do

huynhbaoan

Different from bash, PowerShell is object-orriented. Understanding objects are necessary to utilize PowerShell

 Get-NetIPAddress -AddressFamily IPV4 -AddressState Preferred -IncludeAllCompartments | Get-Member


   TypeName: Microsoft.Management.Infrastructure.CimInstance#ROOT/StandardCimv2/MSFT_NetIPAddress

Name                      MemberType     Definition
----                      ----------     ----------
ifIndex                   AliasProperty  ifIndex = InterfaceIndex

huynhbaoan

###
### This gist contains 2 files : settings.json and lambda_function.py
###

### settings.json
{
    "extensions" : ["*.hdr", "*.glb", "*.wasm"]
}

### lambda_function.py

huynhbaoan

# Stack size check for HTTPD thread
ps aux | grep "[h]ttpd" | awk '{print $2}' > /tmp/httpd.list
while IFS= read -r line
do
    echo "$line"
    cat /proc/$line/status
    ls /proc/$line/task | xargs -I % bash -c "cat /proc/$line/task/%/status" | grep VmStk
done < /tmp/httpd.list
rm -f /tmp/httpd.list
### Since on all thread of process share everything except stack, we only check VmStk here

huynhbaoan

# Create user-defined overlay network
Prerequisites:
Firewall rules for Docker daemons using overlay networks
You need the following ports open to traffic to and from each Docker host participating on an overlay network:
"TCP port 2377 for cluster management communications
TCP and UDP port 7946 for communication among nodes
UDP port 4789 for overlay network traffic"
Before you can create an overlay network, you need to either initialize your Docker daemon as a swarm manager using: docker swarm init
or join it to an existing swarm using: docker swarm join
Either of these creates the default ingress overlay network which is used by swarm services by default. You need to do this even if you never plan to use swarm services. Afterward, you can create additional user-defined overlay networks.

huynhbaoan

Concept

• People talk about two servers: a web server (e.g. Nginx, Apache, etc.) and a app server (e.g. Language specific servers like Unicorn, Node.js, Tomcat, Http-Kit, etc.). There are exceptions where app servers not required at all (as web server itself provides preprocessors for handling), but let's not talk about now.
• Web servers are really fast and supports lot of standard and commonly used MIME-type requests. Concept of serving a file is -- forming and sending a response of bytes of data and labeling it with requested MIME-type by a client (e.g. web browser).
• Every response format (in layman's language, a file) is recognized by it's MIME-type, for e.g. a PNG image file has "image/png" MIME-type. JavaScript file has "text/javascript". HTML responses (or files) has "text/html". Plain text files have "text/plain".
• Modern Browsers supports a lot of standard MIME-types. Images, videos, text files (XML, HTML, SVG, JS), and they better know how to visualize it. Browser also knows unrec

huynhbaoan

proxy_cache_path /tmp/cacheapi levels=1:2 keys_zone=microcacheapi:100m max_size=1g inactive=1d use_temp_path=off;
server {
    listen 443 ssl http2 default_server;
    listen [::]:443 ssl http2 default_server;
    server_name example.com;

    location /api/ {
        # Rate Limiting
        limit_req zone=reqlimit burst=20; # Max burst of request

huynhbaoan

#!/bin/bash

set -u
set -e

set -o pipefail

export PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

cat <<'EOF' > /etc/modprobe.d/blacklist-ipv6.conf

huynhbaoan

### Handling error example 

import sys
import traceback

try:
    f = open('myfile.txt')
    s = f.readline()
    i = int(s.strip())
except OSError as err: