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Python 3.9 comes as a default with Fedora 34. However, sometimes you may wish to install older versions for development and test purposes. Apart from groupinstall command, these instructions work for CentOS and REHL systems as well.

Prerequisites

Install python development dependencies.

sudo dnf groupinstall "Development Tools"
sudo dnf install python3-devel openssl-devel zlib-devel bzip2-devel sqlite-devel libffi-devel

Note: You will need to rebuild and reinstall if you install new source or development libraries for python. Do not create or modify symlinks for python, python3, etc, as that may and will break many dependent libraries in your system.

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Configure Git to use a proxy

In Brief

You may need to configure a proxy server if you're having trouble cloning or fetching from a remote repository or getting an error like unable to access '...' Couldn't resolve host '...'.

Consider something like:

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Enable systemd in WSL 2

This guide will enable systemd to run as normal under WSL 2. This will enable services like microk8s, docker and many more to just work during a WSL session. Note: this was tested on Windows 10 Build 2004, running Ubuntu 20.04 LTS in WSL 2.

• To enable systemd under WSL we require a tool called systemd-genie

• Copy the contents of install-sg.sh to a new file /tmp/install-sg.sh:

  cd /tmp

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Some examples of SNAT, DNAT with iptables with comments

mainly used in start-up script

How to test 'safely'

When we play with iptables aka firewall we might end up in situation, where we execute rule, which has unforseen impact - lock yourself out. Recovering from this situation is necessity.

How to:

• Enable reboot via SMS.
• Test all commands in shell first before putting them into Start-up script. This way the command will be wiped out, when unit is rebooted.

masquarade all outgoing packets to be WLAN0 IP

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package main

import (
	"fmt"
	"net"
	"os"
	"syscall"
)

const (

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# This systemd service configuration will ensure that your service will
# attempt to restart your service FOREVER instead of the systemd default
# of 5 failed retries within 10 seconds and then giving up forever.

[Unit]
Description=MY AMAZING SERVICE
After=multi-user.target

# NOTES ABOUT THE StartLimitBurst OPTION:
# systemd default is StartLimitBurst=5 (give up after 5 failed attempts)

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#!/usr/bin/python3

# Quick Sort 快速排序
# 基于《算法导论》第七章

import random

A = []
for i in range(1000000):
    A.append(random.randint(0, 999999))

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import sys
import json

from ansible.parsing.dataloader import DataLoader

try:
    from ansible.inventory.manager import InventoryManager
    A24 = True
except ImportError:
    from ansible.vars import VariableManager

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tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

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Ubuntu Auto Install

This allows user to do automated installation of ubuntu. Provided here a a few different files/scripts for making this easier.

I've used this to verify that d-i kernel and initramfs from -proposed work as shown in bug 1511497.

The provided 'preseed' below can be used as a fully automated installation of ubuntu. Boot with qemu like:

note python web server is useful for this (python -m SimpleHTTPServer 9999)