Creating the root file system to use with Kernel 4.9.13-MarioTPC

Creating the root file system to use with Kernel 4.9.13-MarioTPC

[mariotpc@fedora31 boot]$ ls
bootp  compressed  dts  Image  install.sh  Makefile  zImage

1.- Create the rootfs
*********************************************************************************
[mariotpc@fedora31 boot]$ mkdir ~/rootfs
[mariotpc@fedora31 boot]$ cd ~/rootfs
[mariotpc@fedora31 rootfs]$ mkdir bin dev etc home lib proc sbin sys tmp usr var
[mariotpc@fedora31 rootfs]$ mkdir usr/bin usr/lib usr/sbin
[mariotpc@fedora31 rootfs]$ mkdir -p var/log
[mariotpc@fedora31 rootfs]$ ls
bin  dev  etc  home  lib  proc  sbin  sys  tmp  usr  var
[mariotpc@fedora31 rootfs]$ tree -d
.
├── bin
├── dev
├── etc
├── home
├── lib
├── proc
├── sbin
├── sys
├── tmp
├── usr
│   ├── bin
│   ├── lib
│   └── sbin
└── var
    └── log

15 directories

2.- Move the rootfs and change everything to root:root 
*********************************************************************************
[mariotpc@fedora31 rootfs]$ cd ~/rootfs

[mariotpc@fedora31 rootfs]$ sudo chown -R root:root *
[sudo] password for mariotpc: 

3.- I am copying the files from busybox to my rootfs
[mariotpc@fedora31 rootfs]$ ~/Downloads/arm/gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf/bin/arm-linux-gnueabihf-readelf -a ../Downloads/busybox-1.27.2/busybox | grep "inter"
      [Requesting program interpreter: /lib/ld-linux-armhf.so.3]

[mariotpc@fedora31 rootfs]$ ~/Downloads/arm/gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf/bin/arm-linux-gnueabihf-readelf -a ../Downloads/busybox-1.27.2/busybox | grep "Shared"
 0x00000001 (NEEDED)                     Shared library: [libm.so.6]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]

[mariotpc@fedora31 rootfs]$ ls lib/ -ltrah
total 24M
lrwxrwxrwx  1 mariotpc mariotpc   12 Mar 21  2019 libm.so.6 -> libm-2.28.so
-rwxr-xr-x  1 mariotpc mariotpc 6.2M Mar 21  2019 libm-2.28.so
lrwxrwxrwx  1 mariotpc mariotpc   12 Mar 21  2019 libc.so.6 -> libc-2.28.so
-rwxr-xr-x  1 mariotpc mariotpc  16M Mar 21  2019 libc-2.28.so
lrwxrwxrwx  1 mariotpc mariotpc   10 Mar 21  2019 ld-linux-armhf.so.3 -> ld-2.28.so
-rwxr-xr-x  1 mariotpc mariotpc 1.3M Mar 21  2019 ld-2.28.so
drwxrwxr-x 13 mariotpc mariotpc 4.0K Aug 24 18:47 ..
drwxrwxr-x  2 root     root     4.0K Aug 24 19:31 .

4.- MKNOD to create the console and null 
***************************************************************************
only two nodes to boot BusyBox: console and null . 
console only needs to be accessible by root , the owner of the device node, so the access permissions are 600 .

[mariotpc@fedora31 rootfs]$ cd ~/rootfs
[mariotpc@fedora31 rootfs]$ sudo mknod -m 666 dev/null c 1 3
[mariotpc@fedora31 rootfs]$ sudo mknod -m 600 dev/console c 5 1

[mariotpc@fedora31 rootfs]$ ls -ltra dev
total 8
drwxrwxr-x 13 mariotpc mariotpc 4096 Aug 24 18:47 ..
crw-rw-rw-  1 root     root     1, 3 Aug 24 19:35 null
crw-------  1 root     root     5, 1 Aug 24 19:35 console
drwxrwxr-x  2 root     root     4096 Aug 24 19:35 .

5.- Mount the proc and sys pseudofilesystems

# mount -t proc proc /proc
# mount -t sysfs sysfs /sys

Something bad occurs here

[mariotpc@fedora31 rootfs]$ sudo mount -t proc proc /proc
mount: /proc: proc already mounted on /proc.
[mariotpc@fedora31 rootfs]$ mount -t sysfs sysfs /sys
mount: only root can use "--types" option
[mariotpc@fedora31 rootfs]$ sudo mount -t sysfs sysfs /sys
mount: /sys: sysfs already mounted on /sys.



Tranfer the rootfs to the initram
***************************************************************************************
1.- Enter to the rootfs
*******************************************
cd ~/rootfs

2.- create the file initramfs.cpio
*******************************************
[mariotpc@fedora31 rootfs]$ sudo find . | cpio -H newc -ov --owner root:root > ../initramfs.cpio
.
./tmp
./usr
./usr/lib
./usr/bin
./usr/sbin
./var
./var/log
./sys
./lib
./lib/libc.so.6
./lib/libm-2.28.so
./lib/ld-linux-armhf.so.3
./lib/libc-2.28.so
./lib/ld-2.28.so
./lib/libm.so.6
./bin
./dev
./dev/console
./dev/null
./proc
./etc
./sbin
./home
47471 blocks
[mariotpc@fedora31 rootfs]$ 

3.- compress it in gzip format
************************************
cd ..
ls -ltr
drwxrwxr-x  13 mariotpc mariotpc    4096 Aug 24 18:47 rootfs
-rw-rw-r--   1 mariotpc mariotpc 7662314 Aug 24 19:39 initramfs.cpio.gz

4.- Try with the previously created kernel
***************************************************
my pwd
/home/mariotpc/Downloads/Embedded/linux-4.9.13/arch/arm/boot

qemu-system-arm -m 256M -nographic -M vexpress-a9 -kernel zImage -append "console=ttyAMA0,115200 \
selinux=0 panic=1" -dtb ./dts/vexpress-v2p-ca9.dtb -initrd /home/mariotpc/initramfs.cpio.gz 


At least my Kernel Works
***********************************************
qemu-system-arm -M vexpress-a9 -kernel zImage -dtb ./dts/vexpress-v2p-ca9.dtb  -initrd initrd.img-3.2.0-4-vexpress -drive if=sd,file=debian_wheezy_armhf_standard.qcow2 -append "root=/dev/mmcblk0p2"

https://people.debian.org/~aurel32/qemu/armhf/
I wanto to try again to create the initrd image...!!!

It finally Works !!!!
************************************************
qemu-system-arm -m 256 -M versatilepb -cpu arm926 -dtb /boot/dtbs/4.9.13-MarioTPC/versatile-pb.dtb -kernel zImage -append "console=ttyAMA0,115200 rdinit=/bin/sh" -initrd ./test3/initramfs.gz

/ # uname -a
Linux (none) 4.9.13-MarioTPC #1 Thu Aug 27 10:19:00 CST 2020 armv5tejl GNU/Linux
/ # busybox 
BusyBox v1.22.0-MarioTPC (2020-08-27 19:41:26 CST) multi-call binary.
BusyBox is copyrighted by many authors between 1998-2012.
Licensed under GPLv2. See source distribution for detailed
copyright notices.

Last steps
*****************************
1.- Mount the proc pseudodevice
mount -t proc proc /proc

/ # mount -t proc proc /proc
/ # ps
PID   USER     TIME   COMMAND
    1 root       0:01 /bin/sh
    2 root       0:00 [kthreadd]
    3 root       0:00 [ksoftirqd/0]
    5 root       0:00 [kworker/0:0H]
    6 root       0:00 [kworker/u2:0]
    7 root       0:00 [lru-add-drain]
    8 root       0:00 [netns]
    9 root       0:00 [oom_reaper]
   10 root       0:00 [writeback]
   11 root       0:00 [kcompactd0]
   12 root       0:00 [crypto]
   13 root       0:00 [bioset]
   14 root       0:00 [kblockd]
   15 root       0:00 [rpciod]
   16 root       0:01 [kworker/0:1]
   17 root       0:00 [xprtiod]
   18 root       0:00 [kswapd0]
   19 root       0:00 [nfsiod]
   26 root       0:00 [bioset]
   27 root       0:00 [bioset]
   28 root       0:00 [bioset]
   29 root       0:00 [bioset]
   30 root       0:00 [bioset]
   31 root       0:00 [bioset]
   32 root       0:00 [bioset]
   33 root       0:00 [bioset]
   34 root       0:00 [bioset]
   35 root       0:00 [bioset]
   36 root       0:00 [bioset]
   37 root       0:00 [bioset]
   38 root       0:00 [bioset]
   39 root       0:00 [bioset]
   40 root       0:00 [bioset]
   41 root       0:00 [bioset]
   42 root       0:00 [kworker/0:2]
   43 root       0:00 [kworker/u2:1]
   68 root       0:00 ps
/ # cat /proc/cpu
cpu/     cpuinfo
/ # cat /proc/cpuinfo 
processor	: 0
model name	: ARM926EJ-S rev 5 (v5l)
BogoMIPS	: 944.53
Features	: swp half thumb fastmult vfp edsp java 
CPU implementer	: 0x41
CPU architecture: 5TEJ
CPU variant	: 0x0
CPU part	: 0x926
CPU revision	: 5

Hardware	: ARM-Versatile (Device Tree Support)
Revision	: 0000
Serial		: 0000000000000000
/ # 


2.- Mount the sys  pseudodevice
**********************************
/ # mount -t sysfs sysfs /sys
/ # ls /sys
block     class     devices   fs        module
bus       dev       firmware  kernel    power
/ # 


NOTES:

Kernel was compiled using:
gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf

Busybox was compiled using:
cross-compiler-armv6l