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# Installing Qt for Embedded Linux

This document describes how to install Qt for Embedded Linux in your development environment:

- Step 1: Installing the License File (commercial editions only)
- Step 2: Unpacking the Archive
- Step 3: Building the Library
- Step 4: Adjusting the Environment Variables
- Step 5: Building the Virtual Framebuffer

Please see the cross compiling and deployment documentation for details on how to install Qt for Embedded Linux on your target device.

Note also that this installation procedure is written for Linux, and that it may need to be modified for other platforms.

### Step 1: Installing the License File (commercial editions only)

If you have the commercial edition of Qt for Embedded Linux, the first step is to install your license file as `$HOME/.qt-license`.

For the open source version you do not need a license file.

### Step 2: Unpacking the Archive

First uncompress the archive in the preferred location, then unpack it:

     cd <anywhere>
     gunzip qt-embedded-linux-commercial-src-4.4.2.tar.gz
     tar xf qt-embedded-linux-commercial-src-4.4.2.tar

This document assumes that the archive is unpacked in the following directory:

     ~/qt-embedded-linux-commercial-src-4.4.2

### Step 3: Building the Library

Before building the Qt for Embedded Linux library, run the `./configure` script to configure the library for your development architecture. You can list all of the configuration system's options by typing `./configure -help`.

Note that by default, Qt for Embedded Linux is configured for installation in the `/usr/local/Trolltech/QtEmbedded-4.4.2` directory, but this can be changed by using the `-prefix` option. Alternatively, the `-prefix-install` option can be used to specify a "local" installation within the source directory.

The configuration system is also designed to allow you to specify your platform architecture:

     cd  ~/qt-embedded-linux-commercial-src-4.4.2
     ./configure -embedded [architecture]

In general, all Linux systems which have framebuffer support can use the `generic` architecture. Other typical architectures are `x86`, `arm` and `mips`.

Note: If you want to build Qt for Embedded Linux for use with a virtual framebuffer, pass the `-qvfb` option to the `configure` script.

To create the library and compile all the demos, examples, tools, and tutorials, type:

     make

On some systems the `make` utility is named differently, e.g. `gmake`. The `configure` script tells you which `make` utility to use.

If you did not configure Qt for Embedded Linux using the `-prefix-install` option, you need to install the library, demos, examples, tools, and tutorials in the appropriate place. To do this, type:

     su -c "make install"

and enter the root password.

Note: You can use the `INSTALL_ROOT` environment variable to specify the location of the installed files when invoking `make install`.

### Step 4: Adjusting the Environment Variables

In order to use Qt for Embedded Linux, the `PATH` variable must be extended to locate `qmake`, `moc` and other Qt for Embedded Linux tools, and the `LD_LIBRARY_PATH` must be extended for compilers that do not support `rpath`.

To set the `PATH` variable, add the following lines to your `.profile` file if your shell is bash, ksh, zsh or sh:

     PATH=/usr/local/Trolltech/QtEmbedded-4.4.2/bin:$PATH
     export PATH

In case your shell is csh or tcsh, add the following line to the `.login` file instead:

     setenv PATH /usr/local/Trolltech/QtEmbedded-4.4.2/bin:$PATH

If you use a different shell, please modify your environment variables accordingly.

For compilers that do not support `rpath` you must also extend the `LD_LIBRARY_PATH` environment variable to include `/usr/local/Trolltech/QtEmbedded-4.4.2/lib`. Note that on Linux with GCC, this step is not needed.

### Step 5: Building the Virtual Framebuffer

For development and debugging, Qt for Embedded Linux provides a virtual framebuffer as well as the option of running Qt for Embedded Linux as a VNC server. For a description of how to install the virtual framebuffer and how to use the VNC protocol, please consult the documentation at:

- The Virtual Framebuffer
- The VNC Protocol and Qt for Embedded Linux

Note that the virtual framebuffer requires a Qt for X11 installation. See Installing Qt on X11 Platforms for details.

The Linux framebuffer, on the other hand, is enabled by default on all modern Linux distributions. For information on older versions, see http://en.tldp.org/HOWTO/Framebuffer-HOWTO.html. To test that the Linux framebuffer is set up correctly, use the program provided by the Testing the Linux Framebuffer document.

That's all. Qt for Embedded Linux is now installed.

Customizing the Qt for Embedded Linux Library When building embedded applications on low-powered devices, reducing the memory and CPU requirements is important. A number of options tuning the library's performance are available. But the most direct way of saving resources is to fine-tune the set of Qt features that is compiled. It is also possible to make use of accelerated graphics hardware. Fine-Tuning Features in Qt for Embedded Linux Qt for Embedded Linux Performance Tuning Adding an Accelerated Graphics Driver to Qt for Embedded Linux