Need overlay script to run before /sbin/init

Douglas_Orend · March 17, 2021, 2:31pm

I’m running a modified version of Frank’s Debian 10 OS. I know there is a way to change the init script (as least there is on the Raspberry Pi). By default, it is /sbin/init. How can I change the script location using uBoot.env?

frank-w · March 17, 2021, 2:36pm

Imho you can add this to your bootopts (cmdline)

init=/bin/sh

Douglas_Orend · March 17, 2021, 2:48pm

I’m sorry. I don’t understand. What do I put in the uBoot.env file? /proc/cmdline reads like this:

board=bpi-r2 earlyprintk console=ttyS0,115200 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait vmalloc=496M debug=7 initcall_debug=0 video=1920x1080 console=tty1 fbcon=map:0 drm.debug=0x7

frank-w · March 17, 2021, 3:01pm

if you use my image, uboot builds cmd from some environment vars (e.g. root,console,graphic and bootopts), imho best place for init-option is in bootopts

you can show bootopts in uboot with “printenv bootopts”

in uenv.txt you can do this:

bootopts="$bootopts init=/usr/bin/yourscript.sh"

if this does not work (your /proc/cmdline shows “$bootopts” as string) you can print bootopts in uboot and use its contents instead of variable

Douglas_Orend · March 17, 2021, 3:15pm

Without the quotes did it for me! Thanks, Frank!

frank-w · March 17, 2021, 3:17pm

Ok sorry…afair quotes are needed when do setenv in uboot…

frank-w · March 22, 2021, 7:24am

Do you want to create overlayfs (readonly rootfs + rw overlay)?

Can you post your script (and maybe depencies)?

Douglas_Orend · March 24, 2021, 12:11am

I’ve done some modification on Mark Lister’s overlayRoot.sh script. The only dependency that I’m aware of is initramfs-tools needs to be installed. It is here:

github.com

xptsp/bpi-r2-router-builder/blob/master/files/sbin/overlayRoot.sh

#!/usr/bin/env bash
#  Read-only Root-FS for Raspian using overlayfs
#
#  Created 2017 by Pascal Suter @ DALCO AG, Switzerland to work on Raspian as custom init script
#  (raspbian does not use an initramfs on boot)
#  Modifications listed as 1.2 Mark Lister: github.com/marklister
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#	You should have received a copy of the GNU General Public License
#	along with this program.  If not, see
#	<http://www.gnu.org/licenses/>.

This file has been truncated. show original

I need to write in some code to format the persistent storage upon request at reboot, though… My attempts have so far failed to produce the desired result…

frank-w · March 24, 2021, 6:55am

Initramstools imho create an initramfs,do you load it in uboot/kernel? Maybe this is required to mount/write+umount

Douglas_Orend · March 24, 2021, 9:06am

No, the script only uses certain functions in order to read the /etc/fstab file to properly mount the partitions as required. No initramfs is required for this… This script gets loaded by the kernel, in place of the /sbin/init file, and calls the /sbin/init at the end of the script in order to initialize the rest of the system.

frank-w · March 24, 2021, 9:08am

ok, then the initramfs-depency could be dropped if you got it working

Douglas_Orend · March 25, 2021, 12:54am

I copied the /usr/share/initramfs-tools/scripts/functions file into my repo and altered the script to use instead of the initramfs-tools version. Still boots, so I guess the initramfs-tools dependency can be dropped…

Douglas_Orend · March 25, 2021, 12:54pm

I went a little further and copied only the functions used into the overlayRoot.sh script and removed the script and package dependencies. Still works, so wheeeeee…

There is another file that can be copied as a control file for the overlayRoot.sh script. It is here:

github.com

xptsp/bpi-r2-router-builder/blob/master/files/etc/overlayRoot.conf

# OverlayRoot config file
# What to do if the script fails
# original = run the original /sbin/init
# console = start a bash console. Useful for debugging

#ON_FAIL=original

# Discover the root device using PARTUUID=xxx UUID=xxx or LABEL= xxx  if the fstab detection fails.
# Note PARTUUID does not work at present.
# Default is "LABEL=BPI-ROOT".  This makes the script work out of the box

#SECONDARY_ROOT_RESOLUTION="LABEL=BPI-ROOT"

# The filesystem name to use for the RW partition
# Default ROOT-RW

#RW_NAME=ROOT-RW

# Discover the rw device using PARTUUID=xxx UUID=xxx or LABEL= xxx  if the fstab detection fails.
# Note PARTUUID does not work at present.

This file has been truncated. show original

Douglas_Orend · March 25, 2021, 3:23pm

Got reformatting persistent storage correctly to work with my overlay script…

tomikapc · April 26, 2021, 1:07pm

Dear Douglas_Orend,

I would like to achieve the same thing as you achieved with this script, however for me it is not clear where is the uBoot.env file which I have to modify, where should I put the overlayRoot.sh script you created and how can I rebuild / regenerate the uboot to activate these changes? I also use the debian image created by frank-w.

Thank you for your answer in advance.

Edit: I use BPI-R64, but I believe it works the same way.

frank-w · April 26, 2021, 1:29pm

Uboot config is on BPI-BOOT/bananapi/bpi-r2/linux (or bpi-r64)

file is named uEnv.txt

If it does not exist,create it

Have not found yet time to test it

tomikapc · April 26, 2021, 1:50pm

Thanks for your fast answer. I mounted /dev/mmcblk0p1 (i use the emmc to boot) to /mnt and I found the following files:

I can modify this uEnv.txt file, however I guess I need to include the overlayRoot.sh file somehow into the uImage. How can I do that? This uboot is very new for me, I only used GRUB and initramfs previously to do things before the root gets mounted.

I cloned your repository (https://github.com/frank-w/u-boot/tree/bpi-r64) and built it, but it only created a bin file, I am not sure it has anything to with this uImage.

Thank you again.

Edit: if you can give some keywords which I can google how to create this uImage file that is also awesome. I tried and I found the mkimage command, which requires a -d switch for the data file and I have no idea which file should I use. I guess mkimage is just wrapping the image for uboot, but how do I generate the input data file?

frank-w · April 26, 2021, 2:37pm

no, do not modify uImage (kernel binary)

you pass name of init_process (=your script) as cmdline from uboot to linux (=cmdline) so that this is started instead of probing for /sbin/init and others

so basicly add this line (make sure path and name of yourscript is right) to uEnv.txt

bootopts=$bootopts init=/usr/local/sbin/yourscript.sh

tomikapc · April 26, 2021, 2:43pm

Thank you. I spent 3 days trying to make it work and now I was able to get it up and running. Now I will try the script Douglas_Orend created for the overlay.

tomikapc · April 26, 2021, 2:52pm

I guess the overlay module is not loaded, so I get the following error message, when the script does a modprobe on it:

modprobe: FATAL: Module overlay not found in directory /lib/modules/5.4.0-BPI-R64-Kernel