Runs fennel using a Lua compiled with the same options as the
host system, and with packages set up so it can find all the local
Lua packages
To shorten the dev feedback loop further, allows FENNEL_PATH to be set
on the command line so you can point directly it at the Fennel sources
for some library you're working against instead of having to run
nix-build and compile them to Lua
Previously: the service wrote a timestamp and the receiver
read and parsed it to see if there was new data
Now: the service writes and removes a .lock file to prevent
the receiver reading partial data. The receiver is responsible
for remembering the *previous* state and only updating if it's changed
this is step 1 of min-collect-garbage, no point implementing
deletion ourselves when rm -r exists
(arguably no point in implementing any of it, but this is the bit we
can't do efficiently in bourne shell - it means we're reading the
store-paths list once instead of grepping it afresh for every entry in
/nix/store/)
By using the kernel "nolibc" header to avoid requiring a C library, we
can bring the initramfs size to around 4k
This does involve a tiny bit of inline mips assembly which I'm not
sure about. gcc seems unwilling to generate the code to load $gp at
function entry of main(), so we do it by hand - but I'd rather find
out why gcc doesn't.
systemconfig (a.k.a "activate") is run from the initramfs. Converting
it from a shell script to an executable means it doesn't depend on
there being a shell in the initramfs
the jffs2 filesystem contains only /nix/store and a script which is
run in early init (initramfs) and is responsible for recreating
"traditional" directories (/bin /etc/**/* /var &c) based on the
configuration.
this is tested only in qemu so far and could use some cleanup
we'd like a bit more of the convenience of mksquashfs
(never thought I'd say _that_) for jffs2, in particular
not having to copy all the desired store paths into a
single directory just so we can create an image from them
