I've used this on windows but never used it on linux, could help me with the install I don't get it.

what files have you got ?. for binary you will probably need to copy a shareware or retail doom data file for it to use,
then just run "llxdoom" or "lsdldoom" it will find the wad file if its in the right place .
If you have an opengl capable system you may be able to add "-opengl" as parameter
ie "llxdoom -opengl -width 1024 -height 768"
to run in opengl mode at resolution of 1024x768
you can also specify the location of the wad by adding "-iwad <path to wad>"

Again more info would help

or, if you want some data files for the engine, check out:
http://happypenguin.org/show?FreeDoom
as the name says, its free doom. the levels are tough and some graphics arent done yet, but its pretty neat. also, i suggest you use prboom instead of legacy. just my opinion, since legacy didnt work very well for me.

I just installed Legacy (using the .wad from Ultimate Doom)

I use Slackware 9.1 so you'll probably have to use RPMs for Redhat but here what I did

Download SDL 1.2

tar -zxvf SDLBlahBlahXXX.tar.gz
./configure
make
su
make install
make clean
exit

Download LegacyXXX.tar.gz
tar -zxvf LegacyXXX.tar.gz

Mounted the Ultimate Doom CD and copied the .wad file into the Legacy Folder in my home directory. You have to make sure it is in the correct caps (ie. the ultimate doom .wad was originally DOOM.WAD, I had to rename to doom.wad).

Then ./llxdoom and all goes fine....except random segmentation faults but all the Doom enhancements have these.