qmake: could not find a Qt installation of ''

Question

sudo apt install qt5-default works for me.

$ apt show qt5-default

tells that

This package sets Qt 5 to be the default Qt version to be used when using development binaries like qmake. It provides a default configuration for qtchooser, but does not prevent alternative Qt installations from being used.

You could check path to qmake using which qmake.

Consider install qt4-default or qt5-default depends what version of qt you want use.

You could also use qtchooser - a wrapper used to select between Qt development binary versions.

For others in my situation, the solution was:

qmake -qt=qt5

This was on Ubuntu 14.04 after install qt5-qmake. qmake was a symlink to qtchooser which takes the -qt argument.

As Debian Qt's maintainer please allow me to suggest you to not use qtx-default. Please read qtchooser's man page, the solution is described there. If you are interested in packaging an app you can also take a look at this blog post I made explaining how to do it

# method 1
QT_SELECT=qt5 qmake

# method 2:
export QT_SELECT=qt5
qmake
... more qt commands here

# method 3:
make -qt5

To use Qt 4, just replace the qt5 with qt4

Update 20210202: starting from Debian 11 (bullseye) the packages qtx-default do not longer exist. Same goes for Ubuntu, but I don't know in which specific version. If you know of a package that still has the dependency (mostly non-Debian official packages) please file a bug. Same goes for Wiki pages, etc.

I had this problem building jasmine-headless-webkit Ruby gem. Despite having qt4 installed, qmake (a symlink to qtchooser) insisted it didn't know about a QT installation. OTOH, it was able to list qt4 when asked directly.

This made everything better:

export QT_SELECT=qt4

qtchooser then knew to use qmake-qt4, and so on.

Search where is qmake-qt4:

which qmake-qt4

For example qmake-qt4 is in this path:

/usr/bin/qmake-qt4

Create symbolic link:

cd /usr/local/sbin/
ln -s /usr/bin/qmake-qt4 .
mv qmake-qt4 qmake

Regards

• Install qt using:

  sudo apt install qt5-qmake
  

• Open ~/.bashrc file:

  vim ~/.bashrc
  

• Added the path below to the ~/.bashrc file:

  export PATH="/opt/Qt/5.15.1/gcc_64/bin/:$PATH"
  

• Execute/load a ~/.bashrc file in your current shell

  source ~/.bashrc`
  

• Try now qmake by using the version command below:

  qmake --version