Developing qt application for a remote device - linux

I am not sure if this is a Programming or Linux question so please forgive me! Here is my situation:
I have my own PC (running Lubuntu 64 19.04) which I use as my work desktop. I have installed qt creator and qt 5.13 and everything works fine.
Now I have a mini-pc (intel nuc) which is luckily the same CPU architecture (intel x86-64). So the program will be binary compatible for both machines and allows me to develope and compile on my main machine and then remotely deploy or debug on the mini-pc using something like ssh and scp.
I want to develope some sort of "kiosk" application for this mini-pc. The problem is that it has very little storage (32GB). This kiosk application will save some data so it needs a lot of free space.
Now back to the question: For the mini-pc, I can go with qt-installer and install qt just like how I did it on my desktop. But I want to avoid this and I want only to copy the libraries that my application needs to have as small as footprint possible. So:
Is there a qt 5.13 libraries only package that I can install using
apt-get?
Can I get away with only copying (.so or .a) files to my remote pc
in the application binary folder?
What would be the must professional way?

You can copy only the relevant dependencies. There is a existing project for this purpose, called linuxdeployqt.
According to the official docs:
This Linux Deployment Tool, linuxdeployqt, takes an application as input and makes it self-contained by copying in the resources that the application uses (like libraries, graphics, and plugins) into a bundle.
And more specific:
When used on Qt-based applications, it can bundle a specific minimal subset of Qt required to run the application.
The project is based in the official tool macdeployqt.

Related

Is it possible to compile a Crystal script so it can run on any Linux machine without the user having to download Crystal

There is a Crystal equivalent of OCRA (One-Click Ruby Application Builder) but it's only for Windows and I use Linux.
Crystal unlike Ruby is not interpreted or executed in a virtual machine. Crystal is compiled to native code ahead of execution using the LLVM. Application is started by the operating system not with interpreter.
So yes, onсе compiled app can copy and run for any Linux machine with the same architecture. You may need to install system libs like libssl for use full featured stdlib but it is not critical.
Crystal app is already OCRA (all of included shards will builded into one binary) if you specially have not used dynamic linking.
What to read next:
List of supported platforms
Installation Crystal
Using the Compiler for build app
Crystal reference
And API documentation

Unity 3d installing Standard assets for Linux/Ubuntu

I have installed Unity 3d on my Linux system.I have downloaded the Window version of the standard assets (.exe) since there is no option for installation in Linux, I tried installing the Standard assets(.exe) through wine... but im getting an error that unity requires windows 7 or more... But since this is Linux i cant help it.Is there any other way?
You can't expect .exe program to work on Linux out of the Box without the help of visual machine or some other software such as Wine. You don't even need the exe program to install the Standard Assets. You can get it directly from the Asset store from your Linux.
It's recommended that you use other OS at this time because the Linux version of Unity is still in experimental mode and you may have problems with it in the future.
You just download unity using the following link,
Unity 5.1 for Linux
It will contains standard asset also. Don't forget to select standard assets while installing.

Deploy to Linux

Background:
Im using QT and have visual studio 2012 as my IDE (used the QT plugin for visual studio).
And finally the whole project is done. However due to my .NET background I have no experience when it comes to deploying my project so it can be run on Linux.
Question:
Anyone knowing how to deploy a QT project made in visual studio to linux?
You should install Linux and prepare a Qt development environment on it.You can then copy your project there, compile it and see the results in the real environment. This way you can cope with the minor differences when porting from one OS to another easily.
So don't think of cross compiling your app for Linux on Windows. From a complexity point of view, I think setting up a Linux machine (VM or not) and the necessary environment for Qt is a whole lot simpler than cross compiling bug hunting afterwards. After all you will need a real target environment to finally test your application.
Before you can deploy something you have to compile it for that platform, and here you have two main choiches: either you cross-compile which means you compile it on windows using a set of tools so that your software is built to run on a linux, or you get a linux machine, you copy your entire project over and let Qt for linux do the magic.
Once you have your working binary compiled on linux or for linux then you start thnking about deployoment.
If you really want to be fully linux-compatible and "linux-ally correct" you should distribute your source-code precooked using some tools like "automake" that will make it possible to linux users to compile it on any linux version.
If you do not want to release your source code, you technically can distribute binaries without source code (not sure if you will be ok with licenses) but you have to be aware that there is no standard in linux for distributing binary packages, there are at least 2 main package building standards that are the ubuntu/debian style and red hat (and friends) style.
You are going to find plenty of documentation about all this stuff from cross-compile to automake and of course building debian packages and building red hat rpm packages.

Deploy a Qt Application Binary on Linux, compatible with LSB

I have developed a small application in Qt Creator on Ubuntu 12.04 which I want should run on any other linux distro (mostly different versions of CentOS and ubuntu), just like any portable application on windows does.
I want to be able to simply share the binary file of the Application, and run the application.
I am able to successfully do this in windows, by just building the project in QT Creator and then putting the required libraries in the Application directory and then transfering them to other windows systems.
I searched all over and found out that I should be trying to build the project using LSB(Linux Standard Base) Compatibility, so that it runs on other linux distros. Is that the right way to do this?
I am very new to Qt and also to Linux (dont know much of Shell Scripting).
Thus, I dont know how I should proceed to make the Application LSB Compliant.
I have refered to, the following links:
Distributing Qt-based binaries on Linux and
Deploying Qt applications on Linux but have not beem able to understand what I am suposed to do.
I also found this question here which states a very similar situation as mine, but because I am a novice, I dont know how I should do this.
Moreover, considering that the first two articles were written 6 years back, shouldn't there be a simpler way to deploy Qt apps on the linux platform now?
I also saw something about static linking, is that the way to go?
Isn't there a way by which all of this can be done through Qt Creator itself?
If there is no hope of creating a portable Qt Application for Linux, then is there a way, say a shell script or something that would combine all the steps required to compile the Qt project on another computer and run it. Say, download Qt-SDK if not present, run qmake and make and then the newly compiled application, if not already there, so that the user can run the program just by running one script.
Your problem here is not the Linux Standard Base, but rather the presence or not of the specific version of Qt you need (or a later one).
Exactly like on a Windows machine, a user may have any of Qt installed, or they may not have it at all. On Windows it is easier to check for the presence of a certain version of Qt than it is on Linux, thus it is easier to write install tools that automate the experience.
To solve your problem there are a few ways:
Inform the user that your program requires a certain version of Qt or higher, and let the user handle the problem
Learn how to create packages for every distribution you want to target and create specific packages
Use a program like 0Install or Elf Statifier to create a package/executable containing all the necessary libraries.
The latter is similar to what many Windows and Mac programs do (they include every library they need within the installer), but it is not the preferred way on Linux, which relies heavily on shared libraries.
Making a binary application compatible with any other Linux distro is practically impossible since you will never know in advance which libraries are available in distro X, or what version of that library is available. Even among a single distro (e.g. Ubuntu), binary application are almost never backward-compatible, since anything built on Ubuntu 12.04 will have dependencies on versions libraries which are installed on that version of Ubuntu, and trying to run that binary on Ubuntu 10.04 will most probably fail simply because it doesn't have a recent enough version of glibc or some other necessary library.
However, the idea can be much more implementable if you limit yourself to a finite list of distros and versions of those distros. You can then know which libraries are available for those distros, and aim for the lowest common denominator. I used to maintain a binary application which had to support several distros (Ubuntu, Fedora, OpenSUSE, SLED, Mandriva), and the way I would do it is install the oldest distro I was targeting on my build machine. That way, the binary application would be linked to the oldest versions of the libraries available on those distros. Unless there's a new major version of such a library (which happens quite rarely, and even then, distros usually distribute the previous major version for a while for compatibility purposes), your compiled binary will then be compatible with all your targeted distros.
Therefore, the quick piece of advice I would give for your situation, use the oldest LTS version of Ubuntu which is still supported (10.04 at the moment) for your development, and you should be pretty safe for most recent popular distros. For the application you already developped on Ubuntu 12.04, you should have no problem simply recompiling the same source on 10.04. Understand that you will never however achieve 100% compatibility with a compiled C++ Qt application.
If Qt is not all that important to you, you could use a higher-level or interpreted language such as Python, Java, Perl or Ruby. With such languages, you can usually count on the language implementation already being installed on the target distro.
Deploy an application in Linux is a nightmare, luckily there are some solutions. Check this projects to build a portable binary with all their dependencies bundled:
http://statifier.sourceforge.net/statifier/main.html
http://www.magicermine.com/index.html
http://www.pgbovine.net/cde.html
Another solution is make a portable 0install package:
http://0install.net/
I recomend this solution. Personally I have been problems with the 3 first packagers.

What is Cygwin and how to use it in relation in Android NDK

Hi I am new to android NDK Devlopment.I downloaded Android NDK 4 for windows.I read through the docs.But i am not clear with it.
First thing is that,I want to develop the native file which may be c 0r c++.I think Using Cygwin will come to play.I dont have any idea or how to use cygwin .From the Docs i just read Cygwin is required for Windows platform.Apart from it ,i dont have any knowledge about it.
Not yet started with NDK Concepts.Help Required
Cygwin is a way to make Windows support some linux functionality. If you install cygwin on your windows machine you'd be able to run some linux software on windows (you'd have to recompile it especially for cygwin though). You can find it and more information about it here. There's also a good explanation at the wiki page here.
If the Android NDK needs it I suppose the Android NDK needs some linux functionality or tools to work properly. The other option might be to install Linux on a machine and run the Android NDK on there, it might be better since I assume Linux is the native environment for Android NDK development.
Since you're saying that you're a bit unclear about the NDK, you should probably be aware that as far as I understand you can not build a whole Android app using it, you can only develop bits of it, you will still need to develop at least part of the app to run on top of the Dalvik virtual machine, which, as far as I know, means that you'll have to write that bit in Java. In general I think that you should develop Android apps only in Java unless there is a specific reason to build certain parts of it using the NDK.
From wiki:
Cygwin (pronounced /ˈsɪɡwɪn/,[2] SIG-win) is a Unix-like environment and command-line interface for Microsoft Windows. Cygwin provides native integration of Windows-based applications, data, and other system resources with applications, software tools, and data of the Unix-like environment. Thus it is possible to launch Windows applications from the Cygwin environment, as well as to use Cygwin tools and applications within the Windows operating context.
Cygwin consists of two parts: a Dynamic-link library (DLL) as an API compatibility layer providing a substantial part of the POSIX API functionality, and an extensive collection of software tools and applications that provide a Unix-like look and feel.
So, Cygwin is a set of tools which allows you to emulate a unix-like (or linux) environment on your windows machines.
The NDK is the Android Native Development Kit. It allows you to write parts of your application in native code (C/C++) and integrate them into your application. Your application still runs under the Dalvik VM but it can load shared objects creating using a cross compiler. The NDK contains all the necessary tools and build scripts to generate native code binaries. It's an advanced concept and one you should probably wait on until you fully understand the architecture.
The reason why it requires Cygwin (or some flavor of linux) is because it uses GnuMake and other linux tools such as awk or Nawk. These tools are not available (or are really hard to use) on windows platforms, hence the need for at least Cygwin (though I would advise you do yourself a favor and just install linux).

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