ventil/ro_raspi3_fs
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Milan Toman 20b4ea52e5 Actual override script for RO FS added
2021-04-08 10:10:24 +02:00
build_rpi_sdcard.sh
2 more scripts to help with it?
2021-03-18 11:06:08 +01:00
overlay.sh
Actual override script for RO FS added
2021-04-08 10:10:24 +02:00
README.md
Reorder documents to fit the use
2021-04-08 09:39:32 +02:00

README.md

Docker RO image

Pre-boot

Create base image, simpel

wget https://downloads.raspberrypi.org/raspios_lite_armhf/images/raspios_lite_armhf-2021-01-12/2021-01-11-raspios-buster-armhf-lite.zip

[temelin ro_raspi3_fs]# unzip 2021-01-11-raspios-buster-armhf-lite.zip
Archive:  2021-01-11-raspios-buster-armhf-lite.zip
inflating: 2021-01-11-raspios-buster-armhf-lite.img

[temelin ro_raspi3_fs]# ls -l
total 2267512
-rw-r--r-- 1 root   root   1862270976 11. led 14.08 2021-01-11-raspios-buster-armhf-lite.img
-rw-r--r-- 1 root   root    459635953 11. led 14.11 2021-01-11-raspios-buster-armhf-lite.zip

Mount image partition locally

[temelin ro_raspi3_fs]# fdisk -l 2021-01-11-raspios-buster-armhf-lite.img
Disk 2021-01-11-raspios-buster-armhf-lite.img: 1,73 GiB, 1862270976 bytes, 3637248 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xe8af6eb2

Device                                    Boot  Start     End Sectors  Size Id Type
2021-01-11-raspios-buster-armhf-lite.img1        8192  532479  524288  256M  c W95 FAT32 (LBA)
2021-01-11-raspios-buster-armhf-lite.img2      532480 3637247 3104768  1,5G 83 Linux

Disk offset to be mounted at loopback: part start (8192) * sector size (512) = 4194304

[temelin ro_raspi3_fs]# losetup -o 4194304 /dev/loop0 2021-01-11-raspios-buster-armhf-lite.img
[temelin ro_raspi3_fs]# losetup -o 272629760 /dev/loop1 2021-01-11-raspios-buster-armhf-lite.img

[temelin ro_raspi3_fs]# mkdir root boot
[temelin ro_raspi3_fs]# mount /dev/loop0 boot
[temelin ro_raspi3_fs]# mount /dev/loop1 root

Enable ssh server and permit login via ssh by default

[temelin ro_raspi3_fs]# touch ./boot/ssh

Disable serial console, change root device to generic mmcblk0p2, init a resize when inserted

[temelin ro_raspi3_fs]# echo "console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet init=/usr/lib/raspi-config/init_resize.sh" > ./boot/cmdline.txt
[temelin ro_raspi3_fs]# echo "dtoverlay=disable-bt" >> ./boot/config.txt
[temelin ro_raspi3_fs]# echo "enable_uart=1" >> ./boot/config.txt
[temelin ro_raspi3_fs]# rm ./root/etc/systemd/system/multi-user.target.wants/hciuart.service
[temelin ro_raspi3_fs]# mv ./root/etc/fstab ./root/etc/fstab.bkp
[temelin ro_raspi3_fs]# cat ./root/etc/fstab | sed 's/PARTUUID=[0-9a-z\-]\+\([0-9]\)\ /dev\/mmcblk0p\1/g' > ./root/etc/fstab

Sync / umount

[temelin ro_raspi3_fs]# umount boot root

Additional steps and remarks

  1. UART > HW (already done at copy phase)
  2. GSM - generic - ip config / reboot / setup (netctl, ipspace, network-manager)
    • recommend netctl / ipspace, net manager has dependencies on Gnome.
  3. wahtchdog mod (configuration not known, just installed)
  4. BalenaOS, Hypriot, RTOS, alternatives

    • BalenaOS: Not looking all that bad, customisation not necessary. Need to test kernel availability and modules for HW devices (CAN / Modbus) Has option for a RO file system. Would recommend a Raspberry PI4

    • Hypriot: Dedicated docker image. Does not seem to be actively developed anymore. Non ROFS support out of the box

    • RTOS non-linux standards RTOS would require a complete rewrite. No Java.

    • Arch Linux / ubuntu ...

      Arch: highly customisable, but might be challenging to maintain. Good community support, great tutorials and documentation. Rolling release, no full system upgrades. 64-bit available

      Ubuntu: based on debian, bloated more than others, has dedicated streams to implementthird party / paid / non-opensource code on the fly

      FreeBSD: Similar to arch, pain to get non-FBSD/GPL code signed, verified and implemented. Very lightweight, stable. 64-bit available

Prepare SD card

dd to SDcard

[temelin ro_raspi3_fs]# dd if=./2021-01-11-raspios-buster-armhf-lite.img of=/dev/sdb status=progress
1854296576 bytes (1,9 GB, 1,7 GiB) copied, 377 s, 4,9 MB/s
3637248+0 records in
3637248+0 records out
1862270976 bytes (1,9 GB, 1,7 GiB) copied, 380,898 s, 4,9 MB/s

Post-boot

[raspi /]# sudo apt-get update
[raspi /]# sudo apt-get upgrade
[raspi /]# sudo reboot

Set up country? Wifi needed?

[raspi /]# sudo apt install network-manager #(to get nmcli, 23MB)
[raspi /]# sudo apt remove python3.7 --purge #python3.5 compatible, subject to testing
[raspi /]# sudo apt install watchdog python3.5 openjdk-8-jre #(800 MB additional)

Disable swap

[raspi /]# sudo sync
[raspi /]# sudo swapoff -a
[raspi /]# sudo apt-get purge -y dphys-swapfile
[raspi /]# sudo rm /var/swap
[raspi /]# sudo sync

HCI / UART:

root@raspberrypi:~# ls -l /dev/serial0
lrwxrwxrwx 1 root root 7 Mar 18 16:05 /dev/serial0 -> ttyAMA0
root@raspberrypi:~# ls -l /dev/serial1
lrwxrwxrwx 1 root root 5 Mar 18 16:05 /dev/serial1 -> ttyS0

re-create SDcard image

make image, shrink it (

[temelin ro_raspi3_fs]# e2fsck -f -y -v -C 0 /dev/sdb2
[temelin ro_raspi3_fs]# resize2fs -p /dev/sdb2 2764800K
[temelin ro_raspi3_fs]# parted -s /dev/sdb 'print'
    Model: Multi Flash Reader (scsi)
    Disk /dev/sdb: 32,0GB
    Sector size (logical/physical): 512B/512B
    Partition Table: msdos
    Disk Flags:

    Number  Start   End     Size    Type     File system  Flags
    1      4194kB  273MB   268MB   primary  fat32        lba
    2      273MB   3200MB  2927MB  primary  ext4
[temelin ro_raspi3_fs]# parted -s /dev/sdb 'resizepart 2 3105M'

Create an empty RAW device + partitions

[temelin ro_raspi3_fs]# dd if=/dev/zero of=./ro_img.dd status=progress bs=1M count=2900
[temelin ro_raspi3_fs]# parted -s ./ro_img.dd 'mktable msdos'
[temelin ro_raspi3_fs]# parted -s ./ro_img.dd 'mkpart primary fat32 2048s 257MiB'
[temelin ro_raspi3_fs]# parted -s ./ro_img.dd 'mkpart primary ext4 257MiB 100%'
[temelin ro_raspi3_fs]# parted -s ./ro_img.dd 'print'
    Model:  (file)
    Disk /mnt/ssd2/ro_img.dd: 3041MB
    Sector size (logical/physical): 512B/512B
    Partition Table: msdos
    Disk Flags:

    Number  Start   End     Size    Type     File system  Flags
    1      1049kB  269MB   268MB   primary               lba
    2      269MB   3041MB  2771MB  primary

Create filesystems. Need to mount with offset, again

2048 * 512 = 1048576, 526336 * 512 = 269484032

[temelin ro_raspi3_fs]# fdisk -l ./ro_img.dd
    Disk ./ro_img.dd: 2,83 GiB, 3040870400 bytes, 5939200 sectors
    Units: sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disklabel type: dos
    Disk identifier: 0xded84696

    Device       Boot  Start     End Sectors  Size Id Type
    ./ro_img.dd1        2048  526335  524288  256M  c W95 FAT32 (LBA)
    ./ro_img.dd2      526336 5939199 5412864  2,6G 83 Linux


[temelin ro_raspi3_fs]# losetup -o 1048576 /dev/loop0 ./ro_img.dd
[temelin ro_raspi3_fs]# losetup -o 269484032 /dev/loop1 ./ro_img.dd

[temelin ro_raspi3_fs]# mkfs.vfat -F 32 -n BOOT /dev/loop0
[temelin ro_raspi3_fs]# mkfs.ext4 -L rootfs /dev/loop1

[temelin ro_raspi3_fs]# mount /dev/loop0 ./boot
[temelin ro_raspi3_fs]# mount /dev/loop1 ./root
[temelin ro_raspi3_fs]# ls -ld boot_sd || mkdir boot_sd
[temelin ro_raspi3_fs]# ls -ld root_sd || mkdir root_sd
[temelin ro_raspi3_fs]# mount /dev/sdb1 ./boot_sd
[temelin ro_raspi3_fs]# mount /dev/sdb2 ./root_sd
[temelin ro_raspi3_fs]# rsync -auP ./boot_sd/ ./boot/
[temelin ro_raspi3_fs]# rsync -auP ./root_sd/ ./root/

Don't forget to re-do the resize at initial boot

[temelin ro_raspi3_fs]# echo "console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet init=/usr/lib/raspi-config/init_resize.sh" > ./boot/cmdline.txt

RO part - manual

making a RO overlay root fs => enable it in raspi-config

This only adds entries to /boot/cmdline.txt and a different overlay kernel to config.txt By removing it, we can get to RW system manually.

-- This breaks the partition resize process. Manual resize and re-enable RO must be triggered at later stage. Must not do this at image generation / adjust the extension process

[raspi /]# sudo raspi-config nonint do_overlayfs 0

Mounting root as RW?

[raspi /]# sudo losetup -f /dev/mmcblk0p1
[raspi /]# sudo losetup -f /dev/mmcblk0p2
[raspi /]# sudo mount -o rw /dev/loop1 /mnt
[raspi /]# sudo mount -o rw /dev/loop0 /mnt/boot

If you need to mount / update

[raspi /]# sudo chroot /mnt
[raspi /]# sudo mount -t proc /proc proc/
[raspi /]# sudo mount --rbind /sys sys/
[raspi /]# sudo mount --rbind /dev dev/

Docker's overlay2 needs to be a tmpfs - Skipped for now

Docker wants to do some mambo-jumbo inside and does not want overlay, need tmpfs

sudo mount -t tmpfs tmpfs /var/lib/docker

need to copy contents of overlay2?

sudo mount -t tmpfs tmpfs /var/lib/docker
sudo cp -r /mnt/var/lib/docker /var/lib/
cp -r /var/lib/docker/* /mnt/var/lib/docker

Results:

RO FS:

pi@raspberrypi:~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        15G  1.5G   13G  11% /
devtmpfs        430M     0  430M   0% /dev
tmpfs           463M     0  463M   0% /dev/shm
tmpfs           463M  6.2M  456M   2% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           463M     0  463M   0% /sys/fs/cgroup
/dev/mmcblk0p1  253M   48M  205M  19% /boot
tmpfs            93M     0   93M   0% /run/user/1000
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