Awesome
Browser VM
A custom Buildroot config for a Linux x86 VM, meant to be run in the browser as part of browser-shell. The resulting Linux ISO is meant to be run under emulation in the browser via v86, and includes:
- a custom Linux 4.15 kernel, which strips out many unnecessary drivers, modules, etc. and adds Plan 9 filesystem sharing
- a root filesystem and Unix commands via BusyBox
- an ISO-based bootloader (i.e., we create a "DVD" that is booted by v86)
Following the Buildroot customization docs
we create a folder buildroot-v86/
with all the necessary config files,
filesystem overlay, and scripts necessary to build our distribution.
Running via Docker
To build the Docker image use the build.sh
script, or:
$ docker build -t buildroot .
And then to run the build:
$ docker run \
--rm \
--name build-v86 \
-v $PWD/dist:/build \
-v $PWD/buildroot-v86/:/buildroot-v86 \
buildroot
NOTE: we define two volumes to
allow the container to access the v86 config, and also to write the ISO once complete. In the
above I've used $PWD
, but you can use any absolute path.
When the build completes, an ISO file will be places in ./dist/v86-linux.iso
in your source tree (i.e., outside the container).
If you need to re-configure things, instead of just running the build, do the following:
$ docker run \
--rm \
--name build-v86 \
-v $PWD/dist:/build \
-v $PWD/buildroot-v86/:/buildroot-v86 \
-ti \
--entrypoint "bash" \
buildroot
Now in the resulting bash terminal, you can run make menuconfig
and other make commands.
buildroot-v86/
Layout
We define a v86
buildroot "board" via the following files and directories:
+-- board/
+-- v86
+-- linux.config # our custom Linux kernel config (make linux-menuconfig)
+-- post_build.sh # script to copy ISO file out of docker container
+-- rootfs_overlay/ # overrides for files in the root filesystem
+-- etc/
+-- inittab # we setup a ttyS0 console terminal to auto-login
+-- fstab # we auto-mount the Plan 9 Filer filesystem to /mnt
+-- configs/
+-- v86_defconfig # our custom buildroot config (make menuconfig)
+-- Config.in # empty, but required https://buildroot.org/downloads/manual/manual.html#outside-br-custom
+-- external.mk # empty, but required https://buildroot.org/downloads/manual/manual.html#outside-br-custom
+-- external.desc # our v86 board config for make
+-- build-v86.sh # entrypoint for Docker to run our build
If you need or want to update these config files, do the following:
$ make BR2_EXTERNAL=/buildroot-v86 v86_defconfig
$ make menuconfig
...
$ make savedefconfig
$ make linux-menuconfig
...
$ make linux-savedefconfig
Configuration Notes
These are the options I set when configuring buildroot for v86. I'm only specifying the things I set.
$ cd buildroot-2018.02
$ make menuconfig
Then follow these config steps in the buildroot config menu (NOTE: these docs may have drifted from the actual config in the source, so consult that first):
Target options
- Target Architecture: i386
- Target Architecture Variant: pentium mobile (Pentium with MMX, SSE)
Build options
- Enable compiler cache (not strictly necessary, but helps with rebuilds)
Toolchain
- C library: uLibc-ng (I'd like to experiment with musl too)
System configuration
- remount root filesystem read-write during boot (I think this is unnecessary)
- Root filesystem overlay directories: /build/overlay-fs (for etc/inittab)
Kernel
- Linux Kernel: true
- Defconfig name: i386
- Kernel binary format: bzImage (vmlinux seemed to break on boot)
Target packages
Need to figure this out. I tried adding imagemagik, git, uemacs, but they are all adding too much size to the image.
Filesystem images
- cpio the root filesystem (for use as an initial RAM filesystem)
- initial RAM filesystem linked into the linux kernel (not sure I need this, trying without...)
- iso image
- Use initrd
- tar the root filesystem Compression method (no compression)
Bootloaders
- syslinux
- install isolinux
Linux configuration
Now configure the Linux Kernel:
$ make linux-menuconfig
And set the following options to accomplish this:
CONFIG_NET_9P=y
CONFIG_NET_9P_VIRTIO=y
CONFIG_9P_FS=y
CONFIG_9P_FS_POSIX_ACL=y
CONFIG_PCI=y
CONFIG_VIRTIO_PCI=y
CONFIG_PCI=y
CONFIG_VIRTIO_PCI=y
Processor type and features
- Processor family (Pentium-Pro) also tried Pentium M before.
Bus options (PCI, etc.)
- PCI Debugging: true (I want to see what's happening with PCI errors, normally not needed)
Networking support
- Plan 9 Resource Sharing Support (9P2000) (built into kernel * vs. M)
- 9P Virtio Transport (* - make this is on, it won't exist if virtio is off)
- Debug information (* - optional)
Device Drivers
- Virtio drivers
- PCI driver for virtio devices (built into kernel * vs. M)
- Support for legacy virtio draft 0.9.X and older devices (New)
- Platform bus driver for memory mapped virtio devices (* vs. M) - not sure I need this...
- Memory mapped virtio devices parameter parsing - or this...
- PCI driver for virtio devices (built into kernel * vs. M)
Filesystems
-
Caches
- General filesystem local caching manager (*)
- Filesystem caching on files (*)
- General filesystem local caching manager (*)
-
Network File Systems
- Plan 9 Resource Sharing Support (9P2000) (*)
- Enable 9P client caching support
- 9P Posic Access Control Lists
- Plan 9 Resource Sharing Support (9P2000) (*)
Now run make
When it finishes, the built image is in ./output/images
.