/mylinux-minimal

A bootable 12 MB Linux with networking

MIT LicenseMIT

mylinux-minimal

A bootable 12 MB Linux with networking

Features:

  • 64-bit Linux OS.
  • Modern UEFI 64-bit boot.
  • GUID Partition Table (GPT).
  • Supports DHCP and networking.

Build OS

Debian 10.

```
parallels@debian-gnu-linux-10:~$ uname -a
Linux debian-gnu-linux-10 4.19.0-17-amd64 #1 SMP Debian 4.19.194-3 (2021-07-18) x86_64 GNU/Linux
parallels@debian-gnu-linux-10:~$ cat /etc/issue
Debian GNU/Linux 10 \n \l
parallels@debian-gnu-linux-10:~$ id
uid=1000(parallels) gid=1000(parallels) groups=1000(parallels),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev),109(netdev),112(bluetooth),116(scanner)
```

Build

  1. Preparations:

    $ sudo mkdir /data
$ sudo chown $USER:`id -gn $USER` /data

$ WORKDIR=/data/mylinux
$ mkdir $WORKDIR
$ cd $WORKDIR/

  2. Compile Linux Kernel:

    • Download:

      $ mkdir $WORKDIR/kernel
$ cd $WORKDIR/kernel/
$ wget https://kernel.org/pub/linux/kernel/v5.x/linux-5.13.12.tar.xz
$ tar xvf linux-5.13.12.tar.xz
$ cd linux-5.13.12/

    • Preparations:

      $ sudo apt install -y flex bison libssl-dev bc libelf-dev
- Clean:
     $ make mrproper
- Create .config:
     $ make defconfig
- Edit .config:
     $ vi .config

    • Build kernel:

      $ make bzImage
...
  OBJCOPY arch/x86/boot/vmlinux.bin
  HOSTCC  arch/x86/boot/tools/build
  BUILD   arch/x86/boot/bzImage
Kernel: arch/x86/boot/bzImage is ready  (#1)

$ ls -al $WORKDIR/kernel/linux-5.13.12/arch/x86/boot/bzImage

    • Generate kernel headers:

      $ rm -rf $WORKDIR/kernel_headers
$ mkdir $WORKDIR/kernel_headers
$ sudo apt install -y rsync
$ make INSTALL_HDR_PATH=$WORKDIR/kernel_headers headers_install

  3. Compile glibc:

    • Download:

      $ mkdir $WORKDIR/glibc_src
$ cd $WORKDIR/glibc_src/
$ wget https://ftp.gnu.org/gnu/glibc/glibc-2.33.tar.bz2
$ tar xvf glibc-2.33.tar.bz2
$ cd glibc-2.33/

    • Preparations:

      $ sudo apt install -y gawk

    • Compile:

      $ rm -rf $WORKDIR/glibc_obj
$ mkdir $WORKDIR/glibc_obj
$ cd $WORKDIR/glibc_obj/
$ $WORKDIR/glibc_src/glibc-2.33/configure --prefix= --with-headers=$WORKDIR/kernel_headers/include --without-gd --without-selinux
$ make

    • Copy:

      $ rm -rf $WORKDIR/glibc
$ mkdir $WORKDIR/glibc
$ make install DESTDIR=$WORKDIR/glibc

  4. Create sysroot:

    $ rm -rf $WORKDIR/sysroot
$ mkdir $WORKDIR/sysroot
$ cp -r $WORKDIR/glibc/* $WORKDIR/sysroot/
$ cp -r $WORKDIR/kernel_headers/include $WORKDIR/sysroot/
$ mkdir $WORKDIR/sysroot/usr
$ ln -s ../include $WORKDIR/sysroot/usr/include
$ ln -s ../lib $WORKDIR/sysroot/usr/lib

  5. Compile busybox:

    • Download:

      $ mkdir $WORKDIR/busybox_src
$ cd $WORKDIR/busybox_src/
$ wget https://busybox.net/downloads/busybox-1.34.0.tar.bz2
$ tar xvf busybox-1.34.0.tar.bz2
$ cd busybox-1.34.0/

    • Build:

      $ make distclean
$ make defconfig
$ vi .config
  Replace:
  CONFIG_SYSROOT=""
  with:
  CONFIG_SYSROOT="/data/mylinux/sysroot"

  Replace:
  CONFIG_EXTRA_CFLAGS=""
  with:
  CONFIG_EXTRA_CFLAGS="-L/data/mylinux/sysroot/lib"

$ make busybox
  Output:
  ...
    CC      util-linux/volume_id/xfs.o
    AR      util-linux/volume_id/lib.a
    LINK    busybox_unstripped
  Trying libraries: crypt m resolv rt
   Library crypt is not needed, excluding it
   Library m is needed, can't exclude it (yet)
   Library resolv is needed, can't exclude it (yet)
   Library rt is not needed, excluding it
   Library m is needed, can't exclude it (yet)
   Library resolv is needed, can't exclude it (yet)
  Final link with: m resolv

    • Copy:

      $ rm -rf $WORKDIR/busybox
$ mkdir $WORKDIR/busybox
$ make CONFIG_PREFIX="/data/mylinux/busybox" install

  6. Create rootfs:

    • Create:

      $ rm -rf $WORKDIR/rootfs
$ cd $WORKDIR/
$ tar xvzf rootfs_overlay.tgz
$ mv rootfs_overlay rootfs

$ cp -r $WORKDIR/busybox/* $WORKDIR/rootfs/
$ rm -f $WORKDIR/rootfs/linuxrc
$ mkdir $WORKDIR/rootfs/lib64
$ cp $WORKDIR/sysroot/lib/ld-linux-x86-64.so.2 $WORKDIR/rootfs/lib64/
$ mkdir $WORKDIR/rootfs/lib
$ cp $WORKDIR/sysroot/lib/libc.so.6 $WORKDIR/rootfs/lib/
$ cp $WORKDIR/sysroot/lib/libm.so.6 $WORKDIR/rootfs/lib/
$ cp $WORKDIR/sysroot/lib/libresolv.so.2 $WORKDIR/rootfs/lib/
$ cp $WORKDIR/sysroot/lib/libnss_dns.so.2 $WORKDIR/rootfs/lib/
$ cp $WORKDIR/sysroot/lib/libnss_files.so.2 $WORKDIR/rootfs/lib/
$ ln -s libnss_dns.so.2 $WORKDIR/rootfs/lib/libnss_dns.so
$ ln -s libnss_files.so.2 $WORKDIR/rootfs/lib/libnss_files.so

$ strip --strip-debug $WORKDIR/rootfs/bin/* $WORKDIR/rootfs/sbin/*
$ strip --strip-debug $WORKDIR/rootfs/lib/* $WORKDIR/rootfs/lib64/*

    • Pack rootfs:

      $ rm -f $WORKDIR/rootfs.cpio.xz
$ cd $WORKDIR/rootfs/
$ find . | cpio -R root:root -H newc -o | xz -9 --check=crc32 > $WORKDIR/rootfs.cpio.xz

  7. Create UEFI boot image:

    • Create:

      $ cd $WORKDIR/
$ tar xvzf uefi_overlay.tgz

    • Create uefi.img:

      $ rm -f $WORKDIR/uefi.img
$ truncate -s 12582912 $WORKDIR/uefi.img
$ LOOP_DEVICE_HDD=$(sudo /sbin/losetup -f)
$ echo $LOOP_DEVICE_HDD
/dev/loop0
$ sudo losetup $LOOP_DEVICE_HDD $WORKDIR/uefi.img
$ sudo mkfs.vfat $LOOP_DEVICE_HDD
mkfs.fat 4.1 (2017-01-24)

    • Populate uefi.img:

      $ mkdir $WORKDIR/uefi
$ sudo mount $WORKDIR/uefi.img $WORKDIR/uefi
$ sudo cp -r $WORKDIR/uefi_overlay/* $WORKDIR/uefi/
$ sudo cp $WORKDIR/kernel/linux-5.13.12/arch/x86/boot/bzImage $WORKDIR/uefi/minimal/x86_64/kernel.xz
$ sudo cp $WORKDIR/rootfs.cpio.xz $WORKDIR/uefi/minimal/x86_64/rootfs.xz
$ sudo umount $WORKDIR/uefi
$ rmdir $WORKDIR/uefi

  8. Create ISO image:

    • Pre-requisites: 
      $ sudo apt install -y xorriso
    • Download syslinux: 
      $ mkdir $WORKDIR/syslinux
$ cd $WORKDIR/syslinux/
$ wget https://kernel.org/pub/linux/utils/boot/syslinux/syslinux-6.03.tar.xz
$ tar xvf syslinux-6.03.tar.xz
    • Create: 
      $ rm -rf $WORKDIR/isoimage
$ mkdir -p $WORKDIR/isoimage/boot
$ cp $WORKDIR/uefi.img $WORKDIR/isoimage/boot/
$ xorriso -as mkisofs -isohybrid-mbr $WORKDIR/syslinux/syslinux-6.03/bios/mbr/isohdpfx.bin -e boot/uefi.img -no-emul-boot -isohybrid-gpt-basdat -o $WORKDIR/minimal_linux_live.iso $WORKDIR/isoimage/
    • File $WORKDIR/minimal_linux_live.iso is generated.

Test

  1. Test using Parallels Desktop:

    • Launch "Parallels Desktop".
    • Right click "Parallels Desktop" from the dock, and then click "Control Center".
    • On Parallels "Control Center", click "File > New...".
      • It shows "Installation Assistant".
      • Click "Install Windows or another OS from a DVD or image file". Click "Continue".
      • Click "Choose Manually".
      • Click "Image File". Click "select a file...". Alternatively, you can install from DVD, Image File, or USB Drive.
      • Browse to: minimal_linux_live.iso Click "Open".
      • It says "Unable to detect operating system. Click Continue to proceed anyway or try another source.". Click "Continue".
      • Please select your operating system: Select "Other > Other". Click "OK".
      • Check "[X] Customize settings before installation". Click "Create".
      • On ""Other" Configuration":
        • Click "Hardware" tab.
        • Click "Boot Order".
        • Click "Advanced...".
        • BIOS: EFI 64-bit --> default: Legacy BIOS Click "OK".
        • Close ""Other" Configuration".
      • Click "Continue".
    • The VM boots:
      • It shows "Minimal Linux Live" in the boot menu.

  2. Test using actual Intel desktop:

    • Download Rufus:
    • Burn the .iso file into a USB drive:
      • Double click "rufus-3.18p.exe":
      • There's a warning "Do you want to allow Rufus to check for application updates online?". Click "No".
      • On "Device", it automatically detects our USB drive "Samsung USB (E:) [256 GB]".
      • On "Boot selection", click "SELECT".
      • Browse to: minimal_linux_live.iso Click "Open".
      • There's a window with title "ISOHybrid image detected" and body "The image you have selected is an ISOHybrid, but its creators have not made it compatible with ISO/File copy mode. As a result, DD image writing mode will be enforced.". Click "OK".
      • Make sure "Partition scheme" is "GPT".
      • Click "START".
      • There's a warning "WARNING: ALL DATA ON DEVICE 'Samsung USB (E:) [256 GB]' WILL BE DESTROYED. To continue with this operation, click OK. To quit click CANCEL.". Click "OK".
      • Click "CLOSE".
    • Reboot the desktop.
      • Press "F12" to enter "BOOT MENU". Notice this is very system dependent.
      • Click "UEFI: Samsung Type-C 1100, Partition 1".
      • It shows "Minimal Linux Live" in the boot menu. Then Linux boots up.

How It Works

See how_it_works.md.

Acknowledgement

The steps were inspired from https://github.com/ivandavidov/minimal