AquilaOS

Features

AquilaOS is built toward POSIX.1-2008. Everything below is in the source tree, documented in the kernel's documents and covered by its QEMU test suite, unless it's listed under Not yet.

User space Ports bash curl tcc Lua X dwm Nano-X Doom Base system dash sbase runit nc aqbox C library newlib 4.6 with AquilaOS's system calls system call interface Kernel Processes threads, SMPsignals, jobs Memory COW, pagingbuddy, vmem VFS ext2, minixtmpfs, procfs Network TCP, UDPIPv4, ARP Terminals vt, ptyline discipline Drivers APIC, MSI HPET, TSC ATA e1000 fbdev PS/2 8250, PL011 x86-64 and i386 PCs, aarch64 (QEMU virt)
Figure 1. The parts of AquilaOS, from the hardware up. Everything below the dashed line runs in the kernel.

Architectures

  • x86-64, the default.
  • i386, using up to 768 MiB of memory.
  • aarch64, on QEMU's virt machine: the GIC, the generic timer, the PL031 clock, PSCI and the devicetree. It runs the whole system on one CPU, with its console on the PL011 serial port.

On the PC, AquilaOS boots with Limine, from an ISO image, a hard disk image or directly from QEMU. The kernel keeps its design apart from the machine, in three layers: the kernel, the architecture (the CPU) and the platform (the machine around it). The documents say which parts are x86's or the PC's, and the few places where the line is still blurred.

Kernel

  • A monolithic kernel with processes and threads, and kernel threads of its own.
  • SMP on x86: up to 32 CPUs, found in ACPI's tables. User programs run on every CPU at once; the kernel runs on one at a time, under one kernel lock (smp=off turns it off).
  • Sessions, process groups, controlling terminals and job control.
  • POSIX signals, delivered on the way back to user mode; a handler's frame keeps the FPU state.
  • Virtual memory with copy-on-write, demand paging and mmap, a buddy allocator for pages and a vmem arena for the kernel's objects. Running out of memory is an error, not a panic.
  • User memory is reached only through copyin and copyout: a bad pointer fails with EFAULT instead of crashing the kernel.
  • A clock to the nanosecond, from the invariant TSC or the HPET, and the PIT without them; the wall clock follows the real-time clock.
  • Interrupts through the APIC, with I/O APIC routes from ACPI's tables, shared IRQs and MSI; the 8259 PIC without one.
  • getrandom, /dev/random and /dev/urandom.
  • Debugging: make debug boots the kernel waiting for gdb, and a panic prints a stack trace that mk/backtrace.sh turns into names.

Filesystems
ext2read and write
minixread and write
tmpfsread and write
initramfsa CPIO archive, read only
devfs and devptsdevice files and pseudo-terminals
procfsprocess information, /proc/interrupts

Devices

  • Virtual terminals on the framebuffer or VGA text mode, switched with Alt+F1 to Alt+F6, with graphics and raw keyboard modes as on the Linux console.
  • A VESA framebuffer with the Linux fbdev API.
  • PS/2 keyboard and mouse (/dev/mouse works like Linux's /dev/psaux).
  • ATA hard disks in PIO mode.
  • Serial ports: the 8250 UART (COM1 and COM2) on the PC, ARM's PL011 on aarch64.
  • Intel 8254x Ethernet (e1000), and the 82574L (e1000e) with MSI; on aarch64 too, over PCI Express.
  • PCI through the platform's host bridge: configuration mechanism #1 on the PC, ECAM on aarch64.

Network

  • IPv4, ARP and ICMP, and the loopback interface.
  • TCP following RFC 9293: retransmission, NewReno congestion control, delayed ACKs, Nagle's algorithm and keepalive.
  • UDP and ping sockets, and Unix domain sockets.
  • DHCP with sdhcp, and a DNS resolver in the C library that reads /etc/hosts first and falls back to TCP for long answers.

Base system

As on the BSDs, some third-party software is part of the base system. It's built from upstream sources with the rest of the system.
C librarynewlib 4.6, with AquilaOS's system calls
/bin/shdash 0.5.13
Core utilitiessbase
initrunit 2.3, which also supervises services such as the logins and DHCP
Network toolsOpenBSD's netcat, sdhcp
System toolsaqbox: login, ps, mount, ifconfig, route and others

Ports

Optional software, built with make ports and included in the system image.

PortVersion
bash5.3.20shell
curl8.23.0with Mbed TLS 3.6 and the CA certificates, for HTTPS
tcc0.9.28rca C compiler that builds programs on AquilaOS itself
Lua5.5.1
vis0.9a vi-like editor, on ncurses 6.6
kiloa small text editor
TinyX1.2.0an X server on the framebuffer, started with startx
twm1.0.13.1window manager
dwm6.5window manager
dmenu5.3
st0.9.2terminal emulator
xterm401terminal emulator
MicrowindowsNano-X: windows on the framebuffer, its demos (Nuklear's among them) and nxterm
UnixBench6.0.1ubench, its index without Perl
doomgenericDoom, with Freedoom 0.13, on the framebuffer or in X

The X ports bring their libraries with them: Xlib and XCB, the X Toolkit and Athena widgets, Xft with FreeType and Fontconfig, and the DejaVu and X.Org misc fonts.

Not yet

  • Finer locking than the one kernel lock, and SMP on aarch64.
  • Loadable kernel modules.
  • ext3 and ext4.
  • TCP window scaling, SACK and timestamps.
  • IPv6.