Problem: alt-clicking to move the camera fails to work in Ubuntu and other linux distros. Instead, the entire window is moved on the dekstop. There appear to be a few solutions/workarounds:
Observation: In some versions of Linux, notably Ubuntu 14.04 and LinuxMint 17.x, Alt+Click did work, but there are certain conditions where it will not. The most reproducible condition is when mouse focus it outide the viewer; Alt+Click too quickly and the system behavior will occur. In all conditions, we found that if Firestorm is in focus and Alt is held for a fraction of a second before the click, the camera will behave.
The solution for Unity, (from this SL forum thread):
If you are using KDE as window manager:
There are a few options for GNOME, specifically the dconf settings. One is to install dconf-tools and then use dconf-editor to locate the mouse modifier and change the value.
A command line alternative that does not require installing software is:
gsettings set org.gnome.desktop.wm.preferences mouse-button-modifier "<Super>"
This command will change the modifier key to Super, or the Windows key.
Once set, log out and back in, or reboot, to make the change take effect.
Some versions of Linux may have several configuration files that may augment or compliment one another, and so even after making the changes above, Alt+Click may still not work. We observed this behavior in Ubuntu 14.10. The solution we found was to add the Super key to the command. In other words, Super+Alt+Click causes the camera to behave as expected