Allow Incoming Connection from Specific IP Address or Subnet in UFW

Allow Incoming SSH from Specific IP Address or Subnet

sudo ufw allow from 15.15.15.0/24  to any port 22
sudo ufw allow from 15.15.15.65 to any port 22

Allow Incoming Rsync from Specific IP Address or Subnet

sudo ufw allow from 15.15.15.0/24 to any port 873

Allow All Incoming HTTP and HTTPS

sudo ufw allow proto tcp from any to any port 80,443

Allow MySQL from Specific IP Address or Subnet

sudo ufw allow from 15.15.15.0/24 to any port 3306

Allow MySQL to Specific Network Interface

sudo ufw allow in on eth1 to any port 3306

References
https://www.digitalocean.com/community/tutorials/ufw-essentials-common-firewall-rules-and-commands

Host ASP.NET Core on Linux with Apache

dotnet add package Microsoft.AspNetCore.HttpOverrides

Configure a proxy server

Invoke the UseForwardedHeaders method at the top of Startup.Configure before calling other middleware. Configure the middleware to forward the X-Forwarded-For and X-Forwarded-Proto headers:

// using Microsoft.AspNetCore.HttpOverrides;

app.UseForwardedHeaders(new ForwardedHeadersOptions
{
    ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
});

app.UseAuthentication();
// using System.Net;

services.Configure<ForwardedHeadersOptions>(options =>
{
    options.KnownProxies.Add(IPAddress.Parse("10.0.0.100"));
});

Forwarded Headers Middleware order

Forwarded Headers Middleware should run before other middleware. This ordering ensures that the middleware relying on forwarded headers information can consume the header values for processing. Forwarded Headers Middleware can run after diagnostics and error handling, but it must be run before calling UseHsts:

using Microsoft.AspNetCore.HttpOverrides;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.Configure<ForwardedHeadersOptions>(options =>
{
    options.ForwardedHeaders =
        ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto;
});

var app = builder.Build();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    app.UseForwardedHeaders();
    app.UseHsts();
}
else
{
    app.UseDeveloperExceptionPage();
    app.UseForwardedHeaders();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseAuthorization();

app.MapRazorPages();

app.Run();

Alternatively, call UseForwardedHeaders before diagnostics:

using Microsoft.AspNetCore.HttpOverrides;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.Configure<ForwardedHeadersOptions>(options =>
{
    options.ForwardedHeaders =
        ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto;
});

var app = builder.Build();

app.UseForwardedHeaders();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseAuthorization();

app.MapRazorPages();

app.Run();

Forwarded Headers Middleware options

using System.Net;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.Configure<ForwardedHeadersOptions>(options =>
{
    options.ForwardLimit = 2;
    options.KnownProxies.Add(IPAddress.Parse("127.0.10.1"));
    options.ForwardedForHeaderName = "X-Forwarded-For-My-Custom-Header-Name";
});

var app = builder.Build();

app.UseForwardedHeaders();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseAuthorization();

app.MapRazorPages();

app.Run();

References
https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/linux-apache?view=aspnetcore-5.0
https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/proxy-load-balancer?view=aspnetcore-6.0

Self-hosted gRPC applications

Run your app as a Linux service with systemd

To configure your ASP.NET Core application to run as a Linux service (or daemon in Linux parlance), install the Microsoft.Extensions.Hosting.Systemd package from NuGet. Then add a call to UseSystemd to the CreateHostBuilder method in Program.cs

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .UseSystemd() // Enable running as a Systemd service
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
        });
dotnet publish -c Release -r linux-x64 -o ./publish

/etc/systemd/system/myapp.service

[Unit]
Description=My gRPC Application

[Service]
Type=notify
ExecStart=/usr/sbin/myapp

[Install]
WantedBy=multi-user.target
sudo systemctl daemon-reload
sudo systemctl status myapp
sudo systemctl start myapp.service
sudo systemctl enable myapp

References
https://docs.microsoft.com/en-us/dotnet/architecture/grpc-for-wcf-developers/self-hosted

Set executable file permission on Windows for using in Linux

with Windows Subsystem for Linux

git update-index --chmod=+x myfile.sh

If you frequently work with .sh files and want to ensure they are always marked as executable, you can configure Git to automatically handle this. For example, you can use a .gitattributes file to define rules for specific file types.

*.sh text eol=lf
*.sh executable

a .bat script for Windows that searches for all .sh files in a folder and its subfolders, and then runs the git update-index --chmod=+x command for each file:

@echo off
:: Get the current directory
set "ROOT_DIR=%cd%"

:: Navigate to the current directory
cd /d "%ROOT_DIR%"

:: Loop through all .sh files in the folder and subfolders
for /r %%f in (*.sh) do (
    echo Processing file: %%f

    :: Add the file to the Git index if it's not already tracked
    git add "%%f" 2>nul

    :: Mark the file as executable
    git update-index --chmod=+x "%%f"
)

echo All .sh files in the current directory and subfolders have been marked as executable.
pause

References
https://www.scivision.dev/git-windows-chmod-executable/

Disable swap on Ubuntu

disable swap only for a current session

sudo swapoff -a

Or 

sudo -s
crontab -e

And add

@reboot sudo swapoff -a  

Or ( best solution )

Open fstab file, type sudo nano /etc/fstab in terminal.

File’s contents would look like this:

proc            /proc           proc    nodev,noexec,nosuid 0       0
/host/ubuntu/disks/root.disk /               ext4    loop,errors=remount-ro 0       1
/host/ubuntu/disks/swap.disk none            swap    loop,sw         0       0
#/dev/sda10 /media/ASD  vfat    defaults    0   0
#/dev/sda1  /media/98   vfat    defaults    0   0

Just add hash (#) to the beginning of the swap partition line, so the line looks as:

#/host/ubuntu/disks/swap.disk none            swap    loop,sw         0       0

Reboot your PC

References
https://askubuntu.com/questions/214805/how-do-i-disable-swap

Convert m2ts to mp4, mp4 to webm, mp4 to ogv using ffmpeg

MP4 TO MP4 (MEDIUM)
ffmpeg -i input.mp4 -b 1000000 output.mp4

M2TS TO MP4
ffmpeg -i input.m2ts -vcodec libx264 -crf 20 -acodec ac3 -vf "yadif" output.mp4

MP4 TO WEBM (HIGH)
ffmpeg -i input.mp4 -aq 5 -ac 2 -qmax 25 -threads 2 output.webm

MP4 TO WEBM (MEDIUM)
ffmpeg -i input.mp4 -aq 5 -ac 2 -qmax 35 -threads 2 output.webm

MP4 TO OGV (HIGH)
ffmpeg -i input.mp4 -vcodec libtheora -acodec libvorbis -q:v 6 -q:a 5 output.ogv

MP4 TO OGV (MEDIUM)
ffmpeg -i input.mp4 -vcodec libtheora -acodec libvorbis -q:v 2 -q:a 4 output.ogv

References
https://gist.github.com/vielhuber/cf918eed2b5cc9eaa63f