From Newsgroup: comp.sys.raspberry-pi

I'm sure this is basically easy but I can't find a simple description
of how to do it. If you search for anything about 'boot' and 'USB'
you are immediately flooded with descriptions of how to boot from USB
and that's not what I want.

I have an ancient Pi B+ that does all I need where it is but I'd like
to be less reliant on the SD card. You can't (easily) boot such an
old Pi from USB and I don't really need to, I just want to make it so
that once booted all activity is on a USB drive.

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot
somewhere?
--
Chris Green
·
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From Newsgroup: comp.sys.raspberry-pi

Chris Green <cl@isbd.net> wrote:

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot
somewhere?

That would work, but I think there is an even simpler way:

Put only "bootcode.bin" on a FAT partition on the SD and a complete OS
image on the USB drive.

When you see "/boot/bootcode.bin" on your USB drive being updated,
update the other one too. A script for that should not need dark magic,
but it still is on my to do list.
--
I do not bite, I just want to play.
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From Newsgroup: comp.sys.raspberry-pi

yeti <yeti@tilde.institute> wrote:

Chris Green <cl@isbd.net> wrote:

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot
somewhere?

That would work, but I think there is an even simpler way:

Put only "bootcode.bin" on a FAT partition on the SD and a complete OS
image on the USB drive.

When you see "/boot/bootcode.bin" on your USB drive being updated,
update the other one too. A script for that should not need dark magic,
but it still is on my to do list.

I know it had to be pretty simple! :-) I have some other old Pi
systems lying around here so I can try it on them. The Pi that I
actually want to do this on is in France and I won't be there for a
couple of weeks.

A script to update the bootcode.bin on the FAT drive should be pretty
simple, just put it in /etc/rc.local and it will be run every time you
boot. It won't matter running it if /boot/bootcode.bin hasn't been
updated, though I suppose you might complain that it's writing to the
SD card unnecessarily. OK, use rsync and the file will only be
written if it has changed.
--
Chris Green
·
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From Newsgroup: comp.sys.raspberry-pi


Hello Chris!

23 Jan 25 22:12, you wrote to all:

Maybe this is useful

https://aroundmyroom.com/2018/07/28/update-boot-from-usb-with-hp-microserver- gen8-and-openmediavault/

and gives you hints

I own some HP Gen8 Microservers where you cannot boot (depends on how you want to use the HDD's) from the ODD port, but you can use it to have a disk connected to it for further use

So the trick is to boot from your SD and than tell Grub that it has to use that
device for the rest
so the USB disk (in my instance) was only getting start and than go further to the SATA

But it should not matter if that is SD or USB whatever..

If you start chatgpt.com ..
and ask a question like

how to start from an SD card (initial boot) on a raspberry pi and than the rest
through grub starting to the USB ?

you get also an answer you might be able to use

I'm sure this is basically easy but I can't find a simple description
of how to do it. If you search for anything about 'boot' and 'USB'
you are immediately flooded with descriptions of how to boot from USB
and that's not what I want.

I have an ancient Pi B+ that does all I need where it is but I'd like
to be less reliant on the SD card. You can't (easily) boot such an
old Pi from USB and I don't really need to, I just want to make it so
that once booted all activity is on a USB drive.

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot somewhere?

Dennis


... The network runs on duct tape and dreams.
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From Newsgroup: comp.sys.raspberry-pi

Chris Green <cl@isbd.net> wrote:

A script to update the bootcode.bin on the FAT drive should be pretty
simple, just put it in /etc/rc.local and it will be run every time you
boot. It won't matter running it if /boot/bootcode.bin hasn't been
updated, though I suppose you might complain that it's writing to the
SD card unnecessarily. OK, use rsync and the file will only be
written if it has changed.

I'd probably want to do that after any package updates, because there's a
risk that the firmware files on the SD and USB become out of sync and that could cause a boot failure.

If you ran it on a cron job say once a day using rsync, it would reduce the chances of that happening. Or there may be a hook you can set to run it
after apt upgrade.

Theo
--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

On 23/01/2025 22:12, Chris Green wrote:

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot
somewhere?

AFAICR what you do is simply edit a file and tell it that / is not where
it thinks it is

But it depends on exactly what you want to happen

The boot process is as follows (I think: Others will correct If I've got
it wrong)

The Pi firmware looks on the SD card for a Vfat partition, and in there
is a file called cmdline.txt

e.g.
console=serial0,115200 console=tty1 root=PARTUUID=778a9e44-02
rootfstype=ext4 fs
ck.repair=yes rootwait noswap=1

That file tells the boot loader wher the root directory is to be found
that it is to grab the kernel off

the key thing is root=PARTUUID=

Now if the SD card does not have such a partition, the boot loader will
look to see if e.g. a USB drive has, and use that instead.

Now on whatever partition it uses as the first stage root, it will have /etc/fstab
e.g.

proc /proc proc defaults 0 0 PARTUUID=778a9e44-01 /boot/firmware vfat defaults 0 2 PARTUUID=778a9e44-02 / ext4 defaults,noatime 0 1

And at this point the booting system may, if you want, mount an entirely different root filesystem and carry on.

So if you edit the /etc/fstab on the SD card, and change the PARTUUID to
a different drive, it will mount that instead. And never touch the SD
card afterwards.

The easy way to do that is to boot the thing as normal, edit the fstab
file to match the ID of the USB device and reboot, making sure that
yiou have copied everything on te root partition of the SD card to the USB.

But frankly its almost always easier to install everything on the USB
drive and remove the SDcard altogether.
--
There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact.

Mark Twain

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From Newsgroup: comp.sys.raspberry-pi

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 23/01/2025 22:12, Chris Green wrote:

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot
somewhere?

AFAICR what you do is simply edit a file and tell it that / is not where
it thinks it is

But it depends on exactly what you want to happen

The boot process is as follows (I think: Others will correct If I've got
it wrong)

The Pi firmware looks on the SD card for a Vfat partition, and in there
is a file called cmdline.txt

e.g.
console=serial0,115200 console=tty1 root=PARTUUID=778a9e44-02 rootfstype=ext4 fs
ck.repair=yes rootwait noswap=1

That file tells the boot loader wher the root directory is to be found
that it is to grab the kernel off

Not quite. If you do it this way, the kernel comes from the SD card and the cmdline is the *kernel* command line, ie it tells that kernel where to find
its root FS once it has started. That means you need to ensure that the
kernel on the SD card remains updated, because any kernel on USB storage
will be ignored.

If you did that way, you could set it up with just a FAT /boot partition on
the SD and then your ext4 rootfs on USB, and adjust the cmdline and
/etc/fstab to match. That way any updates would deploy the SD card /boot.

However if you ever want to re-image your rootfs you have to remember that
you also need to re-image your SD and set up this arrangement again.
Otherwise you'd be booting old kernels from SD with your new USB rootfs.

By using bootcode.bin only on SD (something I've not tried), you can use standard OS images on your USB without any changes.
Or you could boot direct from USB on those Pis that support it with no SD.

Theo
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From Newsgroup: comp.sys.raspberry-pi

On 24/01/2025 09:37, Theo wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 23/01/2025 22:12, Chris Green wrote:

Is it simply a matter of leaving /boot on the SD card and changing /
to being a USB drive or does one need to edit something in /boot
somewhere?

AFAICR what you do is simply edit a file and tell it that / is not where
it thinks it is

But it depends on exactly what you want to happen

The boot process is as follows (I think: Others will correct If I've got
it wrong)

The Pi firmware looks on the SD card for a Vfat partition, and in there
is a file called cmdline.txt

e.g.
console=serial0,115200 console=tty1 root=PARTUUID=778a9e44-02
rootfstype=ext4 fs
ck.repair=yes rootwait noswap=1

That file tells the boot loader wher the root directory is to be found
that it is to grab the kernel off

Not quite. If you do it this way, the kernel comes from the SD card and the cmdline is the *kernel* command line, ie it tells that kernel where to find its root FS once it has started. That means you need to ensure that the kernel on the SD card remains updated, because any kernel on USB storage
will be ignored.

Oh yes, you are right there. If you only adjust that line, you will
still have the fstab on the USB drive mounting the SD boot partition in /boot/firmware. So the kernel will get updated OK automagically.

It is however needlessly messy which is why I went all USB/SSD and
ditched the SDcard.

If you did that way, you could set it up with just a FAT /boot partition on the SD and then your ext4 rootfs on USB, and adjust the cmdline and /etc/fstab to match. That way any updates would deploy the SD card /boot.

Yes. Exactly.

However if you ever want to re-image your rootfs you have to remember that you also need to re-image your SD and set up this arrangement again. Otherwise you'd be booting old kernels from SD with your new USB rootfs.

By using bootcode.bin only on SD (something I've not tried), you can use standard OS images on your USB without any changes.
Or you could boot direct from USB on those Pis that support it with no SD.

Ultimately, that is IMHO the better approach. As long as the Pi can
recognise and boot from USB, leave the SD card out altogether.,

IIRC the most successful approach was in the end, for me, to simply
install raspios on the USB drive and forget the SD card altogether.

Later Pis are perfectly happy to try the SD card like an old PC trying a floppy drive, to boot, but on failure simply look at the USB drives.

And the fact that the boot process uses PARTUUID rather then physical
devices means its agnostic between SDCARD and USBdrive.

The only change I made somewhere was to stop the Pi endlessly trying to
access the SDcard that was no longer there.

in /boot/firmware/config.txt

#since we are booting from SSD
# disable constant SD scan
# We wouldn't be here on an SD card boot

dtparam=sd_poll_once

I really do advise people not to try and split between SDcard and USB.
Just install the OS on the USB to start with.

It works with later pis automatically
--
"Anyone who believes that the laws of physics are mere social
conventions is invited to try transgressing those conventions from the
windows of my apartment. (I live on the twenty-first floor.) "

Alan Sokal

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From Newsgroup: comp.sys.raspberry-pi

Theo <theom+news@chiark.greenend.org.uk> wrote:

Chris Green <cl@isbd.net> wrote:

A script to update the bootcode.bin on the FAT drive should be pretty simple, just put it in /etc/rc.local and it will be run every time you boot. It won't matter running it if /boot/bootcode.bin hasn't been updated, though I suppose you might complain that it's writing to the
SD card unnecessarily. OK, use rsync and the file will only be
written if it has changed.

I'd probably want to do that after any package updates, because there's a risk that the firmware files on the SD and USB become out of sync and that could cause a boot failure.

If you ran it on a cron job say once a day using rsync, it would reduce the chances of that happening. Or there may be a hook you can set to run it after apt upgrade.

Yes, agreed. I suppose you could use inotify but I've never really
got on very well with that.
--
Chris Green
·
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From Newsgroup: comp.sys.raspberry-pi

The Natural Philosopher <tnp@invalid.invalid> wrote:

But frankly its almost always easier to install everything on the USB
drive and remove the SDcard altogether.

As I understand it that's not possible with Pi before Pi 2 version 1.2
or something like that. Basically Pi 3 and onwards can simply boot
from USB, earlier ones can't.
--
Chris Green
·
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From Newsgroup: comp.sys.raspberry-pi

On 24/01/2025 12:55, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

But frankly its almost always easier to install everything on the USB
drive and remove the SDcard altogether.

As I understand it that's not possible with Pi before Pi 2 version 1.2
or something like that. Basically Pi 3 and onwards can simply boot
from USB, earlier ones can't.

Yes, that is my understanding also. I think there was a time when you
had to boot from SD and run a comm,and to change a flag in the firmware
to allow USB only boot.

I have a Pi 4B and its supremely ecstatic booting from USB. And it's a
totally simple setup
--
“Progress is precisely that which rules and regulations did not foresee,”

– Ludwig von Mises

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From Newsgroup: comp.sys.raspberry-pi

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 24/01/2025 12:55, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

But frankly its almost always easier to install everything on the USB
drive and remove the SDcard altogether.

As I understand it that's not possible with Pi before Pi 2 version 1.2
or something like that. Basically Pi 3 and onwards can simply boot
from USB, earlier ones can't.

Yes, that is my understanding also. I think there was a time when you
had to boot from SD and run a comm,and to change a flag in the firmware
to allow USB only boot.

I have a Pi 4B and its supremely ecstatic booting from USB. And it's a totally simple setup

Yes, but my original question was (intended anyway) about booting an
early Pi such that it actually runs from USB after booting from the SD
card so that SD card wear isn't an issue.
--
Chris Green
·
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From Newsgroup: comp.sys.raspberry-pi

On 24/01/2025 13:43, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 24/01/2025 12:55, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

But frankly its almost always easier to install everything on the USB
drive and remove the SDcard altogether.

As I understand it that's not possible with Pi before Pi 2 version 1.2
or something like that. Basically Pi 3 and onwards can simply boot
from USB, earlier ones can't.

Yes, that is my understanding also. I think there was a time when you
had to boot from SD and run a comm,and to change a flag in the firmware
to allow USB only boot.

I have a Pi 4B and its supremely ecstatic booting from USB. And it's a
totally simple setup

Yes, but my original question was (intended anyway) about booting an
early Pi such that it actually runs from USB after booting from the SD
card so that SD card wear isn't an issue.

Well I think that has been covered adequately as well.

Hack the boot partition on the SD card to tell it to use the USB for
booting and hack the fstab entry to tell it to remount the USB as root
after booting. Or a combination thereof

The SD card VFAT partition will remain mounted on /boot/firmware and so
can be upgraded automagically

If it has bootcode.bin it should look at the USB to boot from.

Which works with middle aged pis.

Late models I believe don't need bootcode.bin. Very early models cant
boot USB.
There you have no option but to boot onto the SDcard and edit the
SDCARD /etc/fstab to remount the USB drive as root.
--
Climate Change: Socialism wearing a lab coat.

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From Newsgroup: comp.sys.raspberry-pi

On 23/01/2025 17:42, Dennis Slagers wrote:

Maybe this is useful

https://aroundmyroom.com/2018/07/28/update-boot-from-usb-with-hp-microserver- gen8-and-openmediavault/

and gives you hints

I own some HP Gen8 Microservers where you cannot boot (depends on how you want
to use the HDD's) from the ODD port, but you can use it to have a disk connected to it for further use

So the trick is to boot from your SD and than tell Grub that it has to use that
device for the rest
so the USB disk (in my instance) was only getting start and than go further to
the SATA

But it should not matter if that is SD or USB whatever..

This is completely inappropriate for a Raspberry Pi, which does not boot
like a PC using grub.

If you start chatgpt.com ..
and ask a question like

how to start from an SD card (initial boot) on a raspberry pi and than the rest
through grub starting to the USB ?

you get also an answer you might be able to use

More bad advice.

See later in this thread for the actual answer.

---druck
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From Newsgroup: comp.sys.raspberry-pi


Hello druck!

24 Jan 25 21:38, you wrote to me:

On 23/01/2025 17:42, Dennis Slagers wrote:

This is completely inappropriate for a Raspberry Pi, which does not
boot like a PC using grub.

oeps.. my bad ..

So the maybe is: do not try this ..

Thanks for correcting me.

Dennis


... Error 500: It's your problem now.
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From Newsgroup: comp.sys.raspberry-pi

On 24/01/2025 20:55, Dennis Slagers wrote:

Hello druck!

24 Jan 25 21:38, you wrote to me:

dr> On 23/01/2025 17:42, Dennis Slagers wrote:

dr> This is completely inappropriate for a Raspberry Pi, which does not
dr> boot like a PC using grub.

oeps.. my bad ..

So the maybe is: do not try this ..

Thanks for correcting me.

LOL. Yup Arm/broadcomm based Pis 'do it their way'

It goes back to the chips inception as a set top box embedded processpor
--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

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From Newsgroup: comp.sys.raspberry-pi

On Fri, 24 Jan 2025 13:16:36 +0000, The Natural Philosopher wrote:

I have a Pi 4B and its supremely ecstatic booting from USB.

Not to mention, USB sticks seem to be a lot more reliable than SD cards.
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From Newsgroup: comp.sys.raspberry-pi

On Fri, 24 Jan 2025 11:44:19 +0000, The Natural Philosopher wrote:

If you only adjust that line, you will
still have the fstab on the USB drive mounting the SD boot partition in /boot/firmware. So the kernel will get updated OK automagically.

That doesn’t sound right to me. /etc/fstab is interpreted by a userland process (/sbin/init). That only starts running after the kernel has been booted. So mounting the boot partition at this point will make no
difference to your running kernel. (Presumably /boot/firmware might
contain firmware relevant to connected hardware and its drivers, but
that’s a separate issue.)

(Not a Raspberry Pi user, but this should be basic Linux stuff common to
all architectures.)
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From Newsgroup: comp.sys.raspberry-pi

On Fri, 24 Jan 2025 12:52:51 +0000, Chris Green wrote:

I suppose you could use inotify but I've never really got
on very well with that.

Was there some standard command-line tool for that?

I wrote my own Python wrapper <https://gitlab.com/ldo/inotipy> and
have used that in one nontrivial example so far <https://bitbucket.org/ldo17/serve_passwd/>, which I deployed at a
customer’s installation.
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From Newsgroup: comp.sys.raspberry-pi

On Mon, 27 Jan 2025 14:04:07 +0000, The Natural Philosopher wrote:

Yup Arm/broadcomm based Pis 'do it their way'

It goes back to the chips inception as a set top box embedded processpor

Also remember that GRUB depends on BIOS or UEFI, and the former is x86- specific -- not sure about the latter.

Basically, every vendor’s ARM chipset came up with its own way of booting. In the absence of a BIOS-style interface for querying what hardware is available, the Linux kernel is built with a “device tree” structure that hard-codes this information for your specific chipset.

There is now an equivalent spec standardized for the ARM world (adaptation
of UEFI??), but I understand this is only in use on servers with AArch64,
and the Raspberry Pi predates it anyway.
--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

Lawrence D'Oliveiro <ldo@nz.invalid> wrote:

On Fri, 24 Jan 2025 12:52:51 +0000, Chris Green wrote:

I suppose you could use inotify but I've never really got
on very well with that.

Was there some standard command-line tool for that?

Yes, it's in package inotify-tools and provides CLI commands like
inotifywait and inotifywatch.
--
Chris Green
·
--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

Lawrence D'Oliveiro <ldo@nz.invalid> wrote:

On Mon, 27 Jan 2025 14:04:07 +0000, The Natural Philosopher wrote:

Yup Arm/broadcomm based Pis 'do it their way'

It goes back to the chips inception as a set top box embedded processpor

Also remember that GRUB depends on BIOS or UEFI, and the former is x86- specific -- not sure about the latter.

UEFI isn't x86 specific - Arm uses it as well.

Basically, every vendor’s ARM chipset came up with its own way of booting. In the absence of a BIOS-style interface for querying what hardware is available, the Linux kernel is built with a “device tree” structure that hard-codes this information for your specific chipset.

Yes, although to note that there are typically several stages of booting.
The UEFI / u-boot / etc is often the second or third stage of booting. They come after things like the ROM first-stage bootloader then the second stage bootloader loadered from flash, or similar. Sometimes boot is handled by a
CPU that isn't the main one, such as a 'management' CPU or in the Pi
1/2/3's case the GPU.

In the classic Pi 1, the process is:
1st stage: ROM bootloader (enough to read SD card)
2nd stage: bootcode.bin on SD card (firmware for GPU)
3rd stage: start.elf on SD card (firmware for GPU)
4th stage: Linux kernel from SD card (for CPU)

In Pi 3 and later the ROM bootloader also knows enough to read USB sticks as well as SD cards. The early stage(s) also move to EEPROM on Pi 4 to make
them easier to update.

There is now an equivalent spec standardized for the ARM world (adaptation of UEFI??), but I understand this is only in use on servers with AArch64, and the Raspberry Pi predates it anyway.

It's possible to run another bootloader like u-boot or UEFI as your fourth stage, ie:

1st stage: ROM bootloader (GPU)
2nd stage: bootcode.bin on SD card (GPU)
3rd stage: start.elf on SD card (GPU)
4th stage: UEFI / u-boot on SD card (CPU)
5th stage: Linux kernel (CPU)

This is useful if you need more flexible booting than the regular boot
process provides - eg you want to fetch the kernel from an NFS share, which
is something not supported in the standard Pi firmware.

If the board vendor puts the firmware for stages 1-4 into EEPROM/flash, the board now supports UEFI but the boot process didn't change, it just hid the first four stages from you.

Theo
--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

This is completely inappropriate for a Raspberry Pi, which does not

ot

boot like a PC using grub.

oeps.. my bad ..

So the maybe is: do not try this ..

Thanks for correcting me.

Actually I did read somewhere that it is possible. Technically you only need to use the SD card to boot to init, so modify your /etc/fstab to change the location of your root partition to the device of the USB drive. (Theoretically, I haven't booted my Pi's in quite some time.. rapidly losing interest in running a BBS) ..

--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

* Replying to a msg in PERSONAL.MAIL (PERSONAL.MAIL)


Hello Dave!

26 Feb 25 17:45, you wrote to me:

of the USB drive. (Theoretically, I haven't booted my Pi's in quite
some time.. rapidly losing interest in running a BBS) ..

I've 1 Pi running will never be rebooted unless there is a power outtage. That device is getting through USB my weatherstation data which is than processed by
Weewx and has an FTP session to my website to show me the data ;)


Dennis


... Works fine on my machine.
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From Newsgroup: comp.sys.raspberry-pi

nospam.Dave.Vandermeer@f275.n229.z1.fidonet.org (Dave Vandermeer) wrote:

Actually I did read somewhere that it is possible.

Actually I'm somewhere using this with.
--
I do not bite, I just want to play.
--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

On 28/02/2025 01:35, Dennis Slagers wrote:

* Replying to a msg in PERSONAL.MAIL (PERSONAL.MAIL)

Hello Dave!

26 Feb 25 17:45, you wrote to me:

DV> of the USB drive. (Theoretically, I haven't booted my Pi's in quite
DV> some time.. rapidly losing interest in running a BBS) ..

I've 1 Pi running will never be rebooted unless there is a power outtage. That
device is getting through USB my weatherstation data which is than processed by
Weewx and has an FTP session to my website to show me the data ;)

My CH controller never reboots either.
And only writes to its SD card when the configuration changes.

It comes up perfectly after a power cut...

I am not even interested in keeping it up to date. It does 1 job
supremely well as it is

Dennis

... Works fine on my machine.

--
Renewable energy: Expensive solutions that don't work to a problem that doesn't exist instituted by self legalising protection rackets that
don't protect, masquerading as public servants who don't serve the public.


--- Synchronet 3.20c-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

On 26/02/2025 04:45, Dave Vandermeer wrote:

This is completely inappropriate for a Raspberry Pi, which does not

ot
> dr> boot like a PC using grub.

> oeps.. my bad ..

> So the maybe is: do not try this ..

> Thanks for correcting me.

Actually I did read somewhere that it is possible. Technically you only need to use the SD card to boot to init, so modify your /etc/fstab to change the location of your root partition to the device of the USB drive. (Theoretically, I haven't booted my Pi's in quite some time.. rapidly losing interest in running a BBS) ..

I ended up inadvertently doing this when my Pi wouldn't boot from SSD.
It works, but it's awfully messy.

The SSD had a perfectly fine root partition, but the vfat one was borked somehow.
Cant remember how I deborked it, but it runs fine now...
--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

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From Newsgroup: comp.sys.raspberry-pi

On 26/02/2025 04:45, Dave Vandermeer wrote:

Actually I did read somewhere that it is possible. Technically you only need to use the SD card to boot to init, so modify your /etc/fstab to change the location of your root partition to the device of the USB drive. (Theoretically, I haven't booted my Pi's in quite some time.. rapidly losing interest in running a BBS) ..

The root filing system is determined by what is in cmdline.txt of the
sdcard (or the FAT like filing system on the first device it finds).
What is in /etc/fstab wont change the root filing system in use.

---druck
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From Newsgroup: comp.sys.raspberry-pi

On 28/02/2025 01:35, Dennis Slagers wrote:

I've 1 Pi running will never be rebooted unless there is a power outtage. That
device is getting through USB my weatherstation data which is than processed by
Weewx and has an FTP session to my website to show me the data ;)

With my first Pi (3b), I was paranoid about wearing out the MicroSD card.

I created an NFS share on a NAS server, and mapped most of the Pi's /var partition out to it via fstab. I did other weird stuff moving other
writeable partitions over to the NAS, thus I had a pretty busy network.

Worked well for years, however when I desired to update the OS, decided
life was too short to go though all that again, and instead focused on
an improved backup ritual for the card.
--
Adrian C
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From Newsgroup: comp.sys.raspberry-pi

On 04/03/2025 21:14, druck wrote:

On 26/02/2025 04:45, Dave Vandermeer wrote:

Actually I did read somewhere that it is possible. Technically you
only need
to use the SD card to boot to init, so modify your /etc/fstab to
change the
location of your root partition to the device of the USB drive.
(Theoretically, I haven't booted my Pi's in quite some time.. rapidly
losing
interest in running a BBS) ..

The root filing system is determined by what is in cmdline.txt of the
sdcard (or the FAT like filing system on the first device it finds).
What is in /etc/fstab wont change the root filing system in use.

I am not so sure about that
At some stage during boot, fstab is used to (re) mount all partitions

I *think* that what happened in my case was that the root system was on
SSD., but the linux image itself was from the SD card

---druck

--
In theory, there is no difference between theory and practice.
In practice, there is.
-- Yogi Berra

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From Newsgroup: comp.sys.raspberry-pi

On Wed, 26 Feb 2025 17:45:00 +1300, Dave Vandermeer wrote:

Actually I did read somewhere that it is possible. Technically you
only need to use the SD card to boot to init, so modify your
/etc/fstab to change the location of your root partition to the
device of the USB drive.

The root volume (mounted on “/”) is the one volume that cannot be mounted/dismounted directly in the normal way on a Linux system.
Instead, the kernel offers a special system call, pivot_root(2) <https://manpages.debian.org/pivot_root(2)>, for handling setup of the
root volume.

At boot time, the initial root volume is the contents of the initrd
(“initial RAM disk”) image loaded by the bootloader along with the
kernel. This contains, among other things, some minimal startup script
that interprets the “root=” option that was passed to the kernel as
its command line from the bootloader. At the end of initrd processing,
it finds this volume, mounts it on a temporary directory somewhere,
and uses pivot_root to swap that with the initrd root. The initrd
filesystem (which is not root any more) is now mounted on that
temporary directory and can be dismounted from it in the normal way,
and all further processing can continue with the new root filesystem
as “/”.

In a sense, the entry in /etc/fstab for the filesystem to mount on “/”
is redundant in that it can never be used: accessing it means being
able to open /etc/fstab in the first place, and you can only do that
if the proper “/” is already mounted.
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From Newsgroup: comp.sys.raspberry-pi

Re: How to boot from SD but run from US
By: Dave Vandermeer to Dennis Slagers on Wed Feb 26 2025 17:45:00

Actually I did read somewhere that it is possible. Technically you only need to use the SD card to boot to init, so modify your /etc/fstab to change the location of your root partition to the device of the USB drive. (Theoretically, I haven't booted my Pi's in quite some time.. rapidly losing interest in running a BBS) ..

if you need to and want to know how to setup a raspi to run off a usb drive, while only booting to sd card, let me know. I can respond with instructions. I have ran my raspi using usb drive since raspi b+.

newer raspi devices are easier to setup that way, specifically if you have a newer raspi. the imager that is with the rasp os has an option for what drive to write a new image to.

I've taken my existing os on sd card, put in the usb drive I want to run off of
and wrote out everything to the usb drive, modified the boot config files and /etc/fstab, reboot to run off usb drive.

raspi b can be run this way pretty nice.
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