Teeny Linux

Based on Mitch Galgs instructions on how to build a Linux kernel for qemu, ive made a bash script that will build a linux kernel and busybox ready to go under Qemu or real hardware.

https://gitlab.com/CodeAsm/teeny-linux

• The kernel currently is: 8.8Mb
• The initramfs without other programs but busybox: 694K
• Added musl will grow the initramfs: 78MbWith carefull manipulation, the kernel can be made smaller, so does initramfs

My goals in non particular order are:

• Run Linux on any/most CPU (that qemu offers, and that intrests me ;) ).
• Crosscompile Linux (probably x86_64 as a base).
  • Partial functional
• Have Firewire terminal on PowerPC. (this is part of another project)
• Have small amount of scripts that can build and partialy test various goals
• get a update system working
• smaller compiler for inside (TCC, work has started in a branch)

Most of my research and/or playing is done on a x86_64 Arch Linux system, I asume the reader is skilled enough to translate any commands or hints to their own system or reading other resources to accomplish their own goals.This is never ment for production or replacing LFS for example.

I do not recommend this documentation or scripts as a teaching tool or seen as fact. this is just me playing arround.You can however learn from it, or teach how not to do things.user root, password root

building

run the buildscript :D go to the main project site for more details and howto:https://github.com/CodeAsm/teeny-linux

select arch support comming this feature is being worked on. I want 1 scritp to do all,altho I might consider building the crosstools externaly. so you might need to run that first.

A temporarely ARM target inside crosstools is in the work. requires arm-none-eabi- set of build tools as well as afake init static compiled

Resources

The following resources where used making this project or helped solve problems. “Attribution” as per stackoverflow. as some code might have evolved away from the “answers”, I choose to put the links here under headings of general meaning. The link titles are describtive enough.

• https://gts3.org/2017/cross-kernel.html
• https://balau82.wordpress.com/2010/02/28/hello-world-for-bare-metal-arm-using-qemu/
• https://github.com/netbeast/docs/wiki/Cross-compile-test-application
• http://preshing.com/20141119/how-to-build-a-gcc-cross-compiler/
• http://www.clfs.org/view/CLFS-3.0.0-SYSTEMD/ppc64-64/materials/packages.html
• https://stackoverflow.com/questions/33450401/building-gcc-make-all-error-2
• https://gcc.gnu.org/ml/gcc-help/2012-07/msg00018.html
• https://www.computerhope.com/unix/ucpio.htm
• https://unix.stackexchange.com/questions/56614/send-file-by-xmodem-or-kermit-protocol-with-gnu-screen/65362#65362
• https://www.computerhope.com/unix/ucpio.htm
• https://unix.stackexchange.com/questions/56614/send-file-by-xmodem-or-kermit-protocol-with-gnu-screen/65362#65362
• https://www.lifewire.com/bash-for-loop-examples-2200575
• https://landley.net/aboriginal/bin/
• https://stackoverflow.com/questions/46695403/how-to-add-a-carriage-return-with-sed
• https://blog.christophersmart.com/2016/08/31/configuring-qemu-bridge-helper-after-access-denied-by-acl-file-error/

Bash vs Sh

Some people dislike bash, and set their default shell to something else then bash. This leads to incompatibilities between “scripts” and thus require minor and sometimes mayor code changes to support these different shells.I cannot test them all, but I try to make them compatible. for now, bash is the default.I might consider zsh.

• https://stackoverflow.com/questions/50832481/busybox-sh-wont-exhttps://stackoverflow.com/questions/50832481/busybox-sh-wont-execute-the-bash-scriptecute-the-bash-script

For teenylinux ive swapped to (d)ash (sh like) and this also required profile change:

• https://linux.die.net/man/1/ash
• https://unix.stackexchange.com/questions/176027/ash-profile-configuration-file
• https://www.in-ulm.de/%7Emascheck/various/ash/

VSCode tricks and tips

• https://stackoverflow.com/questions/50569100/vscode-how-to-make-ctrlk-kill-till-the-end-of-line-in-the-terminal

Kernel compiling in general

• https://stackoverflow.com/questions/58924424/why-does-gdb-does-not-show-debug-symbols-of-kernel-with-debug-info
• https://github.com/amezin/vscode-linux-kernel
• https://www.kernel.org/doc/html/v4.10/dev-tools/gdb-kernel-debugging.html
• https://elinux.org/Debugging_The_Linux_Kernel_Using_Gdb
• https://www.starlab.io/blog/using-gdb-to-debug-the-linux-kernel
• https://sourceware.org/gdb/onlinedocs/gdb/Auto_002dloading-safe-path.html
• https://www.kernel.org/doc/Documentation/dev-tools/gdb-kernel-debugging.rst

Compilers

• https://stackoverflow.com/questions/17939930/finding-out-what-the-gcc-include-path-is
• https://stackoverflow.com/questions/2188751/linking-iostream-h-in-linux-using-gcc/2188765#2188765

Crosscompile

• https://gts3.org/2017/cross-kernel.html
• https://balau82.wordpress.com/2010/02/28/hello-world-for-bare-metal-arm-using-qemu/
• https://github.com/netbeast/docs/wiki/Cross-compile-test-application
• https://balau82.wordpress.com/2010/03/22/compiling-linux-kernel-for-qemu-arm-emulator/
• https://designprincipia.com/compile-linux-kernel-for-arm-and-run-on-qemu/

For TinyC Compiler

• https://stackoverflow.com/questions/49391116/build-newlib-with-existing-cross-compiler
• https://wiki.osdev.org/Porting_Newlib
• https://github.com/john-tipper/Cross-compile-toolchain-for-linux-on-OSX/
• https://stackoverflow.com/questions/11307465/destdir-and-prefix-of-make
• https://www.monperrus.net/martin/compiling-c-code-with-dietlibc-and-tcc

Bash tricks

• https://linuxhandbook.com/bash-arrays/
• https://www.cyberciti.biz/faq/finding-bash-shell-array-length-elements/

Resolved a init kernel problem:https://stackoverflow.com/questions/15277570/simple-replacement-of-init-to-just-start-console

timing:

• https://linuxconfig.org/time-your-bash-scripts-and-procedures-from-inside-the-code

Dropbear

• http://wiki.andreas-duffner.de/index.php/Ssh%2C_error:_openpty:_No_such_file_or_directory
• https://serverfault.com/questions/963994/how-to-manually-setup-network-connection-from-busybox-shell-ash
• https://superuser.com/questions/141344/dont-add-hostkey-to-known-hosts-for-ssh