fpinit: Fast parallel init

fpinit is a modified version of sinit which makes use of script to execute init scripts in parallel.

In its current state, fpinit is usable as a system's full-time init, but it (somewhat by design) lacks process supervision, meaning it does nothing other than boot and halt the system.

Demo

fpinit booting Alpine Linux in a QEMU VM:

Compiling and Running

fpinit contains script as a module, meaning:

 $ git submodule update --init --recursive --remote

Will clone the latest version of script (--init is only necessary for first clone). fpinit can be compiled with:

 $ make

And installed with (this will not overwrite any important init scripts or files -- everything is entirely self-contained within /usr/local):

 # make install

To use fpinit as the system init, the kernel parameter:

 init=/usr/local/bin/fpinit

Must be added to the kernel's configuration, likely through bootloader (i.e. GRUB/LILO/Syslinux) or EFI boot entry configuration.

Included Scripts

The scripts available in fpinit.d/ and fphalt.d/ are a stripped-down and modified subset of Void's runit scripts, stali's sinit scripts, and Alpine's openrc scripts, doing slightly more than the absolute minimum necessary for a usable system. Right now, they are tested and intended to work on Alpine, however all Alpine/busybox-specific behavior has alternatives which will be used automatically if necessary. Specifically, this includes:

• agetty: preferred over getty
• mdev: preferred over (e)udev
• udhcpc: preferred over dhcpcd (which is preferred over dhclient)

Additionally, there exist a number of scripts in fpinit.extra.d/ which provide non-essential nice-to-haves (e.g. ntpd, sshd, etc.), with the steps to install them being the same as for user-created scripts (detailed below).

Adding New Scripts

Because script is configuration-free by design, any executable file can be placed into /usr/local/share/fpinit.d/ or /usr/local/share/fphalt.d/. As fpinit lacks process supervision, there is currently no built-in way to create services or recurrent tasks, however POSIX setsid and bash's disown can achieve similar behavior (see 4-tty.sh)

To-Do

• Fix(/investigate) sending SIGINT to busybox udhcpc and login causing system hang