How can I download a Cygwin package (and its dependencies) under Ubuntu?

I developed a backup tool for Windows which uses rsync from Cygwin. I am myself using Ubuntu.

I want to download the Windows rsync package and all other packages it depends on under Ubuntu. Is this possible?

I know the packages are all available via HTTP. But rsync has like 30 dependencies and they can change in each version.

So it's very complicated to download them all by hand.

I want to download the Windows rsync package under Ubuntu.

I am using Ubuntu 21.10.

Edit: This answer was written before OP edited the question to download "Windows rsync package in Ubuntu" (which is confusing). This answer is about how to get rsync in Ubuntu, in case it is removed from the default installation.

The package rsync is available in the Ubuntu repositories. Open a terminal, and enter the command

sudo apt install rsync

APT will automatically take care of all the dependencies, and install rsync.

I think you may be a bit confused because you've started on Windows. Cygwin, if I remember correctly, is a collection of Linux tools ported to Windows - it doesn't exists in Linux, simply because there is no need for it. All the tools you find in Cygwin are native to Linux, so you will find rsync in the Ubuntu repository, if it isn't already installed - to see if it is installed, you can run type rsync from a commandline (type in Linux is completely different from type in Windows - it locates a command or prints a message if it can't find it).

If it isn't there, you can install it with apt, or if you want a GUI interface, use synaptic (which you can install with apt-get install synaptic).

The answers you got are all focusing on getting rsync on Ubuntu, which is of course is trivial. If I understand you right you need the rsync windows executable with all dependencies, to package with your backup tool? So the question could be reworded as: how can I define & download the dependencies of Cygwin rsync. The answer to that question could be to use wine to run Cygwins own package manager, and let that pm figure out the hard stuff. But I've never tried that, so caveat emptor.

Cygwin is a compatibility layer that lets you run Linux programs on the Microsoft Windows operating systems. Ubuntu itself is a Linux operating system, so Linux programs run natively on it. You don't Cygwin.

Rsync might come preinstalled with Ubuntu. To check if you already have rsync installed, open a terminal (command prompt) and enter this command:

rsync --version

If you have it already installed you might get an output which tells you the version, and display a copyright notice and some other details. But if it is not installed it would say something like command rsync not found.

Rsync is available in the official repositories and so can be installed by giving the following commands:

sudo apt-get update
sudo apt-get install rsync -y

There are of course several other ways to do this, including compiling from source and what not.