Buildroot demo of FastInit (Finit)

December 26, 2022 - 3 mins read

I believe there is a gap in the market between BusyBox init and systemd. In particular in the embedded space. This blog post shows how easily it is to get up and running quickly with FastInit (Finit)!

I’m a really bad salesman, and an even worse writer, so instead of trying to convince you with my poor English, I’ve made a demo. It is a Buildroot external that can be used to add Finit to your own projects.

For details, look here: https://github.com/troglobit/br2-finit-demo, try out the latest build in Qemu.

Why Finit?

Sane built-in defaults
Supports runlevels
Respawns your services (customizable)
Scriptable nearly everywhere
Supports service/task synchronization (called conditions)
Supports PID/systemd/s6 readiness notification
Supports tmpfiles.d like systemd
Supports ifup -a & ifdown -a natively
Supports /etc/rc.local and has built-in runparts for SysV init compatibility
And more …

Try it Out

First, check your system for the necessary packages to build a buildroot system https://buildroot.org/downloads/manual/manual.html#requirement

Download the demo GIT repo:

~$ git clone https://github.com/troglobit/br2-finit-demo.git

Change to the top directory and fetch all submodules:

~$ cd br2-finit-demo/
~/br2-finit-demo(main)$ git submodule update --init

Configure and Build

~/br2-finit-demo(main)$ make qemu_x86_64_defconfig
~/br2-finit-demo(main)$ make

Run
```
~/br2-finit-demo(main)$ make run
```
Log in, user root, empty password

It boots fairly quick provided you have an x86_64 host computer. See the initctl tool to control Finit.

# initctl help

Brings up the available commands. Check what is running right now:

# initctl status   # default command, you can omit 'status'

Show available .conf snippets that start services:

# initctl ls

Try enabling some services (not a lot is enabled in the defconfig, add more with make menuconfig or make busybox-menuconfig) like:

# initctl enable telnetd

Try initctl ls again, it’s now listed in the set of enabled services. But it’s not yet running … (check with initctl status). This is because we may want to roll out multiple changes to a system before activating them. To activate we tell Finit to reload its configuration.

# initctl reload

Verify it is now running. For more detailed information about telnetd:

# initctl status telnetd

Try killing telnetd and check the status again. You can now see that Finit has already restarted it for you (Restarts: 1 (1/10)). Kill it a few more times to see what happens. When a service reaches its max restart count Finit will no longer try to restart it automatically – something is obviously not right with the service. You will have to restart it manually, which clears the restart counter. Notice how the total restarts counter continues counting.

You can connect to the system from your host, or anywhere on the LAN:

~$ telnet localhost 8023

Fin

There is of course a lot more to cover. Please get in touch with me if you are curious about some other aspect that would be suitable for a blog post. There is also a discussion forum open for general questions about Finit.