Virtual Embedded Linux Board

Use chemo, the Quick Emulator, to emulate ARM-based boards like Raspberry Pi and BeagleBone Black with chemo system arm, explore supported machines and CPUs via machine help and CPU help.

Learn how qemu uses dynamic binary translation to run a guest system on a host, emulating Raspberry Pi or Beaglebone black with virtual peripherals across x86, ARM, MIPs, and Microblaze.

Learn to build a cross compilation toolchain with crosstool-ng for an embedded linux board. Fetch sources, bootstrap, configure locally, and generate the toolchain for arm.

Learn to create multi-architecture toolchains with cross tooling, selecting cortex a9, arm configurations, and glibc or uclibc, then build and locate the toolchain in the ecs tools folder.

Verify the completed cross-compilation toolchain for arm linux, locate the bin folder with gcc, and access the sysroot containing C libraries, headers, and C++ libraries.

Export the tool chain and compile a hello world C with ARM Linux GCC. Emulate the ARM binary and fix libraries with -L pointing to the tools root.

Delete the build folder by cleaning the toolchain with ct-ng clean to remove temporary build files and downloads, freeing about 12 GB of disk space.

Build and configure the u-boot bootloader for an emulated Cortex-A9 board with a cross toolchain, storing its environment on a fat filesystem via MMC, then boot the kernel.

Run U-Boot on QEMU system arm with VExpress A9, set 128 MB RAM, enable serial logs, and manage environment with setenv and saveenv.

Create a 1 gb virtual sd card image, partition into a 64 mb bootable fat16 partition, a 32 mb rootfs partition, and a linux partition; mount with losetup and format.

Attach an sdcard image to a virtual embedded Linux board using a virtual MMC, configure and save the u-boot environment on the FAT partition, and verify boot-time environment persistence.

Build and load the kernel in a virtual chemo environment, using the dev config for arm and an ARM toolchain, then load the kernel image and dtb; rootfs is missing.

Learn how initramfs uses ramfs to boot Linux quickly, and how to build a simple initramfs with a hello world program and kernel command line append.

Learn how to build a minimal BusyBox root filesystem from an initrd/initramfs by configuring for static libraries, exporting a cross-compile toolchain, and booting with a ramdisk shell.

In the virtual embedded Linux board course, create persistent root filesystem on sd card by building an ext4 rootfs image, copying BusyBox, mounting it, and booting the kernel from rootfs.

Learn how to fix tty errors by mounting the root filesystem, creating four tty character device nodes under /dev (tty1-tty4), then remounting and verifying the root filesystem works.

Configure an mmc boot sd card image by creating a fat boot partition with u-boot env and kernel, plus an ext4 rootfs partition, then copy z image, dtb, and rootfs.

Create an alias to start the virtual board with a short command, mapping start board to the long command, so typing start board boots the board.

Boot the virtual embedded Linux board from bootloader to kernel and rootfs. Create a hello world file, run sync, and verify it persists on the sd card after reboot.

Mount the proc and sysfs virtual file systems on a virtual embedded linux board with mount -t proc and mount -t sysfs. Ensure changes persist by initializing them at startup.

verify a kernel option on an embedded Linux board by inspecting the compressed kernel config in procfs with zcat or grep, and use the ik config utility to extract it.

Mount devtmpfs to /dev with mount -t devtmpfs none /dev, creating and accessing dev nodes; enable automatic mounting in the kernel config and rebuild to have devtmpfs mounted at boot.

Configure BusyBox init with an init tab and init.d script to auto mount proc and sysfs at boot, driven by the kernel’s PID 1 init process.

Learn to start a background daemon on a virtual embedded linux board with inittab. Compile a static daemon, deploy it to the root filesystem, and enable respawn for auto-restart.

Learn how tmpfs, a temporary file system stored in volatile memory, uses RAM and kernel cache to speed file access, with a default size of half the available RAM.

Explore mounting options for temp fs and other partitions, applying the principle of least privilege with ro, rw, remount, and default settings, including no exec, no dev, and no suid.

Learn how fstab acts as a file system configuration table to ease mounting. It defines device, mount point, filesystem type, and options, enabling automatic mounting with mount -a.

Create users on an embedded linux system by editing /etc/passwd and /etc/shadow, assign root uid 0, and use bin false to disable login.

Enable the login prompt on the virtual embedded Linux board using jetty and inittab, then reboot to log in as root or other users and verify home directory behavior.

Create groups by editing the ATC group file in the ATC folder, defining each entry with group name, password, gid, and members, then assign users and verify with id.

Add a password for the root user by generating an encrypted hash with mk password, updating the shadow file with the new hash, and verifying login prompts.

The ATC profile provides a system-wide configuration script executed at login, setting environment variables and initializing the shell for all users, while per-user dot profile customizes each user's environment.

Learn how PS1 defines the primary shell prompt, showing username, host, and current directory; root uses hash and normal users use a dollar sign. Export and profile edits modify PS1.