Deploying Qt Application under Linux

[addu]

I had never deployed Qt application under linux..

My application i have used following module additionally

1) Qt network

2) Qt webkit

3) Qt Sql

I tried with application distribution with following libs along with my application

1) Application folder

1) application
2) libQtGui.so.4
3) libQtCore.so.4
4) libQtNetwok.so.4
5) libQtxml.so.4
6) libQtWebkit.so.4
7)libQtSql.so.4
8) sql drivers folder

But i am getting error message ../Maxxtel could not able to run.

please help me

Thanks

Yuvaraj R

[TMan]

In general, there are two "good" options for this.

1) Use dynamic linking and let people install Qt form their linux software repositories, or
2) Use static linking so people don't need any additional libs (except libc and such obviously)

Which of these are you trying to do? Furthermore, it may help if you post the real error message instead of "could not able to run".

[addu]

till now i have been using dyanamic method under windows

In linux i want use static method .

please explain me about static method.

how do we distribute the application using static method ?

Thanks

Yuvaraj R

[nightghost]

Did you read http://qt.nokia.com/doc/4.5/deployment-x11.html and maybe http://qt.nokia.com/doc/4.5/qt-conf.html?

But i am getting error message ../Maxxtel could not able to run.

What error message? Please help us and give us real example :-)

[squidge]

You can't put dynamic libs in the same directory as the executable under Linux unless you modify the library search path, and even then, a simple library called libQtGui.so.4 will not be used without a symlink to specify the current library version (usually created by installing the library into the system library dir). This will be why you are getting this error. Under Windows it always searches the application path first.

Its much easier to just add the Qt dependancy to your package and distribute that. When people install your app it will automatically install Qt if necessary (which is the preferred way of distributing Linux apps). If you don't want to package your application, then you must use static linking, but this requires you to rebuild Qt and pay Nokia money unless your app is open source.

[addu]

Hi

I opened nighthost mentioned links , but i didn't opned..

How do add Qt dependencies for my package distibution ..

please provide me related links

Thanks

Yuvaraj R

[squidge]

I think you should read this: http://en.wikipedia.org/wiki/Package_management_system for better understanding.

[ChrisW67]

Addu,

Your initial problem with failing to load the program could be helped by some of these:

• Reading the man page for ldd (1) and running it on your executable.
• Reading the man page for ld.so (8) particularly about the environment variable LD_LIBRARY_PATH and also when it is ignored.
• Using a script to wrap your executable and adjust with the LD_LIBRARY_PATH before handling off to your executable.
• Building a statically linked executable (but read and understand your Qt License first).

Without being able to read minds we cannot help you with packaging your product. You need to tell us:

1. Whether you can distribute source or the product is binary only. If you can distribute source, and the end-user can build it, then you may only need to put dependency info in a Readme file. If binary only you need to package using a tool that the target OS can understand so the user does not have to guess.
2. What your target Linux audience is: tech savvy, not tech savvy, people who normally use Windows, paying or non-paying users etc.
3. What distros they are running. Packaging for Ubuntu (Debian), Redhat (CentOS), Gentoo or Slackware is different. Google for dpkg, RPM, ebuild, ...

It almost always helps to tell people what you have already tried, provide exact error messages if that's what you are asking about, provide that actual code of a minimal program that reproduces the fault if possible, explain what you expected to happen etc. Put some effort into asking smart questions and you'll get much more helpful answers.

[schnitzel]

I'm not sure whether this is the best solution, but I was able to deploy on linux (ubuntu 9.04) like this:

create a file myapp.conf in /etc/ld.so.conf.d/
Inside that myapp.conf file, you should list the directory where your application plus libs reside.
For example myapp.conf will contain a single line:
/home/schnitzel/myapp

I believe you have to then run the command ldconfig. This method is way better than futzing around with LD_LIBRARY_PATH.

My app uses dynamic linking so my application folder contains only qt core, gui libs, two third party libs and some plugins.

I still have to wrap my head around creating a package in order to make the install procedure as simple as possible.

Is it possible to create an ubuntu package with only binaries in it?

[ChrisW67]

This method is way better than futzing around with LD_LIBRARY_PATH.

This method affects the system globally and does leave you open to dynamically linking to the first libQtCore.so.4 (a symlink to a specific version like libQtCore.so.4.5.2) the system finds in the ld.so search path. Normally this is not a problem but can be if, for example, you rely on a fix Qt in 4.5.3 and the first Qt that is found is a Qt 4.5.0 because that's in the path earlier. Conversely, your version might be found first and break someone else's app. Binaries I have built tend to link by name to libQtCore.so.4 (i.e. any Qt4 vers) and not libQtCore.so.4.5.2, but there is probably a way to force this if a specific version is required.

The script approach makes the change local to your application. For example this is the wrapper for the Google Earth app on my machine:

#!/bin/sh
cd "/opt/googleearth"
if [ -n "." ] ; then
        if [ "${LD_LIBRARY_PATH+set}" = "set" ] ; then
                export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:."
        else
                export LD_LIBRARY_PATH="."
        fi
fi
exec ./googleearth "$@"

#!/bin/sh
cd "/opt/googleearth"
if [ -n "." ] ; then
        if [ "${LD_LIBRARY_PATH+set}" = "set" ] ; then
                export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:."
        else
                export LD_LIBRARY_PATH="."
        fi
fi
exec ./googleearth "$@"

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[schnitzel]

This method affects the system globally and does leave you open to dynamically linking to the first libQtCore.so.4 (a symlink to a specific version like libQtCore.so.4.5.2) the system finds in the ld.so search path. Normally this is not a problem but can be if, for example, you rely on a fix Qt in 4.5.3 and the first Qt that is found is a Qt 4.5.0 because that's in the path earlier. Conversely, your version might be found first and break someone else's app. Binaries I have built tend to link by name to libQtCore.so.4 (i.e. any Qt4 vers) and not libQtCore.so.4.5.2, but there is probably a way to force this if a specific version is required.

The script approach makes the change local to your application. For example this is the wrapper for the Google Earth app on my machine:

#!/bin/sh
cd "/opt/googleearth"
if [ -n "." ] ; then
        if [ "${LD_LIBRARY_PATH+set}" = "set" ] ; then
                export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:."
        else
                export LD_LIBRARY_PATH="."
        fi
fi
exec ./googleearth "$@"

#!/bin/sh
cd "/opt/googleearth"
if [ -n "." ] ; then
        if [ "${LD_LIBRARY_PATH+set}" = "set" ] ; then
                export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:."
        else
                export LD_LIBRARY_PATH="."
        fi
fi
exec ./googleearth "$@"

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I will try your approach - somehow I was a bit ignorant and thinking the app.conf file would only be relevant to my app.