remove requirement to unplug usb after live session

On rebooting the prompt (paraphrasing) to press Enter then remove usb stick can be eliminated by editing the grub.cfg file.

In order to edit the file you will need to use another linux environment and edit the file /boot/grub/grub.cfg

scroll down to the menu entry you want to use (normally the first one) and where it says "quiet splash" put "noprompt"

I normally remove the "quiet" entry as I like to see what happens during boot.

This was suggested by "Sudodus" at the ubuntu forums, many thanks to him.

@vidtek99,

Glad you got it working.

Make sure you mark your question as "Solved," otherwise Launchpad will automatically delete the question if it remains "Open" for too long.

The main issue is not resolved.

Sudodus solution just removed the prompt, it didn't resolve the main issue of having to physically remove the. usb stick and replug it back in.

After more research, this script written by Patrick Cronin from this answer on Stackechange:

https://askubuntu.com/questions/1036341/unplug-and-plug-in-again-a-usb-device-in-the-terminal

seems to do the trick on a working system, but where would it need to be inserted/called from within a cubic environment to activate on shutdown without hanging the machine?

#!/bin/bash

port="usb1" # replace '1' with actual bus number as shown by lsusb -t: {bus}-{port}(.{subport})

bind_usb() {
  echo "$1" >/sys/bus/usb/drivers/usb/bind
}

unbind_usb() {
  echo "$1" >/sys/bus/usb/drivers/usb/unbind
}

unbind_usb "$port"
# sleep 1 # enable delay here
bind_usb "$port"

OK
That failed miserably. So I tried another tack.

I have been through my mountain of computer stuff and pulled out an Anker 7port with 3 power only usb3 powered hub. https://uk.anker.com/products/a7515

I tried in my workshop to see if when the power was removed the usb hub was reset as though unplugged from the host computer.

It was, the little blue active light went off, the hub was disconnected and I was able to reboot the computer without physically unplugging the usb stick.

So a work-around, not the most elegant solution, a software approach built-in to the live system would have been far more elegant but this works for my application. I have tested it with a smart plug and even using google assistant voice control I was able to achieve my goal.
The timing is critical, disconnect too early in the reboot process and it will cause the machine to hang (as the usb stick is the current o/s), too late and the bios boot process will already have started.

If anyone can come up with a way to achieve the same result by removing the way a live system insists on a replug that would be far better.

Tony.

Tony,

I didn't get a chance to test the shut-down process while using a Live USB plugged into the system.

However, I was thinking of a possible software solution...

Run a script at shutdown to force unmount the USB. (You may also be able to do a "lazy" unmount using `umount -l`, so the system ~thinks~ the drive is not mounted).
This way, the system may not detect that a USB is present, and thus, should not prompt the user to remove it.

@Cubic PPA

Thanks for the suggestion, I tried a couple of shutdown scripts to achieve this, but the problem was they ran on shutdown while the system is still operating from the live system on the usb stick.

It all ends very messy with a completely hung system and pressing the computer power switch off to reset it.

So it's a bit chicken and egg....

That's why using the hardware the poweroff has to be timed critically in the period immediately after the o/s no longer has sway over the system, and re-powered on immediately before the bios is activated.

Not a long time interval, it's about 7 seconds on my machines.

If you are using the `umount` command, try with the `-l` option.

@Cubic PPA

Thanks for the suggestion, it isn't unmounting that's the issue, it's completely resetting this particular USB bus.

The hardware work-around I found is working (after a fashion) I just have to be on my toes to judge the timing correctly.

Cheers Tony.