Added qemu and custom image notes

2 files changed, 176 insertions, 0 deletions

diff --git a/md/writeup.md b/md/writeup.md
index 6cbca88..94ee3ff 100644
--- a/md/writeup.md
+++ b/md/writeup.md
@@ -27,6 +27,7 @@ title: Writeup page
 [Using cgroups](writeup/using_cgroups.md)  
 [Compile static python](writeup/compile_python.md)  
 [Linux hello world in Swift](writeup/linux_hello_world_in_swift.md)  
+[Running disk images in QEMU](writeup/running_disk_images_in_qemu.md)  
 
 
 ## Projects
diff --git a/md/writeup/running_disk_images_in_qemu.md b/md/writeup/running_disk_images_in_qemu.md
new file mode 100644
index 0000000..d4b2d7d
--- /dev/null
+++ b/md/writeup/running_disk_images_in_qemu.md
@@ -0,0 +1,175 @@
+title:Runing disk images in QEMU
+keywords:linux,qemu,raspi,linux,
+
+# Running RasPi4 in QEMU
+
+
+## Intro
+
+Notes how to run in QEMU different images. Its cool to run raspi images
+with qemu, that allows quickly test what is inside shell, what kind of packages
+are missing and if needed test your software.
+
+
+## Runing Raspberry Pi images
+
+### Download image
+
+Download raspi debian kernel
+```
+wget -c https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/kernel-qemu-4.4.34-jessie
+```
+Download  image
+```
+wget -c https://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2017-08-17/2017-08-16-raspbian-stretch-lite.zip
+unzip 2017-08-16-raspbian-stretch-lite.zip
+```
+
+QEMU is using their own file image format lets concert img to qcow2
+```
+qemu-img convert -f raw -O qcow2 2017-08-16-raspbian-stretch-lite.img raspbian-stretch-lite.qcow
+```
+
+Set network on local machine tun0 that will used by qemu to 
+```
+brctl addbr tun0
+brctl addif tun0 enp0s25
+```
+
+Start qemu with raspi4 image
+````
+qemu-system-arm \
+-kernel ./kernel-qemu-4.4.34-jessie \
+-append "root=/dev/sda2 panic=1 rootfstype=ext4 rw" \
+-hda raspbian-stretch-lite.qcow \
+-cpu arm1176 -m 256 \
+-M versatilepb \
+-no-reboot \
+-serial stdio \
+-nic user,hostfwd=tcp::10022-:22
+```
+
+Login to raspi prompt
+
+```
+Username: pi
+Password: raspberry
+```
+
+Getting cursor back
+```
+Ctrl+Alt+g
+```
+
+## Create Image Custom Image
+
+Be careful its your responsibility what you type in terminal.
+
+
+### Create Image
+
+Create image 128MB in size, with 2 partitions ext2 and ext4, install grub2.
+
+```
+dd if=/dev/zero of=disk.img bs=1048576 count=128
+parted --script disk.img mklabel msdos mkpart p ext2 1 64 mkpart p ext4 64 128 set 1 boot on 
+
+kpartx -a disk.img
+
+mkfs.ext2 /dev/mapper/loop0p1
+mkfs.ext4 /dev/mapper/loop0p2
+
+
+mkdir /mnt/disk0
+mount /dev/mapper/loop0p1 /mnt/disk0/
+grub-install --target=i386-pc --recheck --no-floppy --root-directory=/mnt/disk0 --modules="biosdisk part_msdos ext2 configfile normal multiboot" /dev/loop0
+
+nano /mnt/disk0/boot/grub/grub.cfg
+umount /mnt/disk0
+kpartx -d disk.img
+```
+
+### Installing GRUB2
+
+Installing grub
+
+```
+grub-install --target=i386-pc --recheck --no-floppy --root-directory=/mnt/disk0 --modules="biosdisk part_msdos ext2 configfile normal multiboot" /dev/loop0
+```
+
+After grub installation create config with some minimal entries, and point to kernel that was
+copied to partition. Kernel for test could taken from __/boot__ directory.
+How to compile kernel its different story.
+
+```bash
+## Begin /boot/grub/grub.cfg
+set default=1
+set timeout=5
+
+probe -u $root --set=rootuuid
+set imgdevpath="/dev/disk/by-uuid/$rootuuid"
+
+menuentry "GNU/Linux, vmlinux" {
+        linux   /vmlinux root=/dev/sdb2 ro
+}
+
+```
+
+Not sure why it works with sdb2 but not with sda1.
+
+
+### Launch
+
+Now image is ready to be launched from qemu. Use any kernel image you like,
+this will boot tills stage where kernel will ask to set "init=" parameter.
+
+Booting image from local filesystem, all kernel output goes to shell.
+```bash
+qemu-system-x86_64 \
+    -kernel diskimages/bzImage \
+    -hda disk.img \
+    -append "root=/dev/sdb2 console=ttyS0" \
+    -serial stdio -display none \
+    -m 128
+```
+
+
+Booting just from img file
+```bash
+qemu-system-x86_64 \
+    -drive format=raw,file=disk.img 
+    -m 128
+```
+
+If shell fails with this output. Then everything booting succeed.
+
+```bash
+"---[ end Kernel panic - not syncing: No working init found.  Try passing init= option to kernel. See
+Linux Documentation/admin-guide/init.rst for guidance. ]---"
+```
+
+Next step is to figure out what to do with this info, maybe make your own distro?
+Create some cool ass crypto drive? Or just have fun.
+
+## References to other articles
+
+[01] [http://main.lv/writeup/compile_linux_kernel.md](http://main.lv/writeup/compile_linux_kernel.md)  
+[02] [http://main.lv/writeup/qemu_usage.md](http://main.lv/writeup/qemu_usage.md)  
+
+## Links
+
+[01] [https://blog.agchapman.com/using-qemu-to-emulate-a-raspberry-pi/](https://blog.agchapman.com/using-qemu-to-emulate-a-raspberry-pi/)  
+[02] [https://github.com/dhruvvyas90/qemu-rpi-kernel.git](https://github.com/dhruvvyas90/qemu-rpi-kernel.git)  
+[03] [https://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2017-08-17/2017-08-16-raspbian-stretch-lite.zip](https://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2017-08-17/2017-08-16-raspbian-stretch-lite.zip)  
+[04] [https://downloads.raspberrypi.org/](https://downloads.raspberrypi.org/)  
+[05] [https://github.com/dhruvvyas90/qemu-rpi-kernel/tree/master/tools](https://github.com/dhruvvyas90/qemu-rpi-kernel/tree/master/tools)  
+[06] [/writeup/qemu_usage.md](/writeup/qemu_usage.md)  
+[07] [https://en.wikibooks.org/wiki/QEMU/Images](https://en.wikibooks.org/wiki/QEMU/Images)  
+[08] [https://wiki.archlinux.org/index.php/QEMU](https://wiki.archlinux.org/index.php/QEMU)  
+[09] [https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842054/QEMU+-+Zynq-7000](https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842054/QEMU+-+Zynq-7000)  
+[10] [https://linux-tips.com/t/booting-from-an-iso-image-using-qemu/136](https://linux-tips.com/t/booting-from-an-iso-image-using-qemu/136)  
+[11] [https://roscopeco.com/2013/08/12/creating-a-bootable-hard-disk-image-with-grub2/](https://roscopeco.com/2013/08/12/creating-a-bootable-hard-disk-image-with-grub2/)  
+[12] [https://www.centennialsoftwaresolutions.com/post/build-the-linux-kernel-and-busybox-and-run-them-on-qemu](https://www.centennialsoftwaresolutions.com/post/build-the-linux-kernel-and-busybox-and-run-them-on-qemu)  
+[13] [https://en.wikibooks.org/wiki/QEMU/Images](https://en.wikibooks.org/wiki/QEMU/Images)  
+[14] [https://wiki.gentoo.org/wiki/QEMU/Linux_guest](https://wiki.gentoo.org/wiki/QEMU/Linux_guest)  
+[15] [https://www.cs.vu.nl/~herbertb/misc/writingkernels.txt](https://www.cs.vu.nl/~herbertb/misc/writingkernels.txt)