Problem: I Installed Texmaker, but I could not find the Xelatex command.
Solution: I went to some forums and they said I should check by hand, running
"xelatex XXX.tex". Surprisingly, The tool is even uninstalled.
Then just running "apt-get install texlive-xetex" as root, and add customized command "xelatex -synctex=1 -interaction=nonstopmode %.tex" by hand.
Easy, right?