First install ghdl and gtkwave:
$ sudo apt-get install ghdl gtkwave
See the fine http://ghdl.free.fr/ghdl/index.html for the rest
Remember to compile with the “–ieee=synopsys -fexplicit” option if you want to use non-standard packages, such as std_logic_arith.
You can also compile a whole project. First compile all the files to a executable named work:
$ ghdl -i --ieee=synopsys -fexplicit --workdir=work *.vhdl
Then make the design
$ ghdl -m --ieee=synopsys -fexplicit --workdir=work name_of_design
You can then run the design
$ ghdl ./name_of_design
Which is great for testing.