install notes (mac version)

INSTALL-xv6.md

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+
+# Install Notes
+
+To get xv6 up and running on your machine, you'll need a few tools
+installed. Here, we'll walk you through what you need to do.
+
+## The xv6 Source Code
+
+To obtain the xv6 source code, just clone it from github:
+
+```sh
+prompt> git clone https://github.com/mit-pdos/xv6-public
+loning into 'xv6-public'...
+remote: Enumerating objects: 13974, done.
+remote: Total 13974 (delta 0), reused 0 (delta 0), pack-reused 13974
+Receiving objects: 100% (13974/13974), 17.15 MiB | 2.73 MiB/s, done.
+Resolving deltas: 100% (9534/9534), done.
+prompt> cd xv6-public
+```
+
+There! Now you have completed the easiest part.
+
+## MacOS Build Environment for xv6
+
+To play with xv6 on a Mac, you'll need to install two pieces of software. The
+first is the [`qemu`](https://www.qemu.org/download/) machine simulation
+environment. 
+
+What is a simulator? TBD.
+
+Why use one?
+
+To install `qemu` on a Mac, just do the following:
+
+```sh
+prompt> sudo port install qemu
+```
+
+This will take a little while, so pour yourself a cup of coffee and enjoy. 
+
+This command assumes you have [MacPorts](https://www.macports.org/)
+installed. If you don't, go to the [MacPorts install
+page](https://www.macports.org/install.php) and follow instructions first. 
+
+Th command further assumes that the path to port (usually `/opt/local/bin`) is
+in your path. You should probably add this directory to your path anyhow; the
+`qemu` software will get installed there too.
+
+When finished, you should be able to run the `qemu` software. To run the x86
+version (which is what is needed for xv6), type the following command:
+
+```sh
+prompt> qemu-system_x86-64 -nographic
+```
+
+This will run the `qemu` emulator, but with no kernel to boot! Alas, not that
+useful. 
+
+To quit `qemu`, type `C-a x` (that is, hold down `control` and while doing so,
+press `a`, then let go of `control`, then press `x`). 
+
+The second piece of software you'll need is the `gcc` cross-compilation
+toolchain. To install these pieces of software, type:
+
+```sh
+prompt> sudo port install i386-elf-gcc gdb
+```
+
+When you're done, you're ready to try to build and run xv6. Change into the
+`xv6-public` directory, and type:
+
+```sh
+prompt> make TOOLPREFIX=i386-elf- qemu-nox
+```
+
+If all has worked well, you'll see something like:
+
+```sh
+Booting from Hard Disk..xv6...
+cpu1: starting 1
+cpu0: starting 0
+sb: size 1000 nblocks 941 ninodes 200 nlog 30 logstart 2 inodestart 32 bmap
+sta8
+init: starting sh
+$
+```
+
+The `$` is the shell command prompt: who-hoo! 
+
+Remember to type `C-a x` to quit the emulation.
+
+A couple of quick edits might be useful to the xv6 `Makefile`. First, change
+the `TOOLPREFIX` line to uncommented, and to look as follows:
+
+```sh
+TOOLPREFIX = i386-elf-
+```
+
+This will all you to type the following simpler `make` command:
+
+```sh
+prompt> make qemu-nox
+```
+
+Note: `qemu-nox` is the way this `Makefile` allows you to build and run xv6
+without spinning up a separate window, but rather running `qemu` directly
+within your terminal, which we prefer. If you want the new window to pop up
+instead, just run `make qemu`.
+
+We also usually edit the `Makefile` to use one CPU (not two). Look for the
+line that says:
+
+```sh
+CPUS := 2
+```
+
+and change it to:
+
+```sh
+CPUS := 1
+```
+
+Now, time to go do the projects!
+
+
+## Linux
+
+TBD.