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This provides an quick overview of how the GNU/Hurd system starts, and thus how
it is structured.

# Grub

The GNU/Hurd system uses multiboot, and thus usually booted from grub, which
loads into memory the GNU Mach kernel, the ext2fs server (see later), and the
exec server (see later). It then gives hand to GNU Mach, passing ext2fs and exec
as payloads.

# GNU Mach

GNU Mach initializes a basic console, and tasks, memory management and
interprocess communication (details can be read on
[[microkernel/mach/gnumach/boot_trace]]).  It also initializes drivers for
disk. It then creates two tasks for the ext2fs and exec servers.

# ext2fs

ext2fs is given as a parameter the name of the device of the root filesystem. It
opens it through the GNU Mach disk driver, and mounts the filesystem found on
it. When it is ready, it can start booting the system by starting the "startup",
"proc", and "auth" servers. It does so by using the "exec" server already loaded
by GNU Mach: "exec" handles loading the binaries of the three new servers, just
like it will handle loading binaries in the GNU/Hurd system in general. We then
have a posixish environment, ext2fs gives hand to "startup".

# proc

Proc knows about processes: what pid they have, passing signals, managing tty
sessions, etc.

# auth

Auth knows about identities: uid, gid, etc.

# startup

"startup" is the unixish system starting point: it basically runs /sbin/init, at
which point we end up with the standard Unix boot up.

# netdde / pfinet

At some point of the boot process, networking will have to be configured. This
is done by starting "pfinet", the TCP/IP stack, from /servers/socket/2, which
itself starts the network device driver server, "netdde", from /dev/netdde.

# everydaylife

Normal processes use glibc to interact with the system. Depending on the kind of
call, glibc will perform RPCs with the various servers mentioned above: opening
files will trigger RPCs with ext2fs, calling getpid() and such will trigger RPCs
with proc, calling getuid() and such will trigger RPCs with auth, opening a
network socket will trigger RPCs with pfinet.

One can read the [[details how reading a file happens|hurd/io_path]].