Move running and debugging to doc/build.md

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

doc/build.md

@@ -85,6 +85,50 @@ Linux config to:
   system `/etc/fstab`.
 
 
+Running
+-------
+
+Having successfully built Finit it is now be time to take it for a test
+drive.  The `make install` attempts to set up finit as the system system
+init, `/sbin/init`, but this is usually a symlink pointing to the
+current init.
+
+So either change the symlink, or change your boot loader (GRUB, LOADLIN,
+LILO, U-Boot/Barebox or RedBoot) configuration to append the following
+to the kernel command line:
+
+```shell
+append="init=/sbin/finit"
+```
+
+Remember to also set up an initial `/etc/finit.conf` before rebooting!
+
+
+Debugging
+---------
+
+Add `finit_debug`, or `--debug`, to the kernel command line to enable
+debug messages.
+
+```shell
+append="init=/sbin/finit --debug"
+```
+
+To debug startup issues, in particular issues with getty/login, try
+`configure --enable-fallback-shell`.  When no TTYs are detected, and
+Finit is configured with this option, Finit will try to start a bare
+`/bin/sh` on the boot console.  Remember, this is only for debugging
+and would leave your production system potentially wide open.
+
+There is also a rescue shell available, in case Finit crashes and the
+kernel usually reboots: `configure --enable-emergency-shell`.  However,
+the behavior of Finit is severely limited when this is enabled, so use
+it only for debugging start up issues when Finit crashes.
+
+**NOTE:** Neither of these two configure options should be enabled on
+  production systems since they can potentially give a user root access.
+
+
 [1]:       ftp://troglobit.com/finit/finit-3.0.tar.xz
 [libuEv]:  https://github.com/troglobit/libuev
 [libite]:  https://github.com/troglobit/libite