[TUHS] Unix install & "standalone" package

[TUHS] Unix install & "standalone" package

[Paul Ruizendaal via TUHS]

Recently, I was looking into the “Das U-Boot” boot loader package. Summarised with great simplification, u-boot bundles device drivers, file systems, commands and a Bourne-like shell into a standalone package. Normally it auto-runs a script that brings up a system, but when used in interactive mode it allows a great deal of poking around.

It made me think of the “standalone” set of programs for installing early Unix. On 16-bit understandably each basic command has to be a separate standalone program, but after the shift to 32-bit bundling more functionality in a single binary would have become possible.

How did the Unix “standalone” package evolve in the 80’s, both in the research and BSD lineages? Is there any retrospective paper about that? Or is it a case of “Use the source, Luke”?

[TUHS] Re: Unix install & "standalone" package

[emanuel stiebler]

On 2023-09-04 05:57, Paul Ruizendaal via TUHS wrote:
> 
> Recently, I was looking into the “Das U-Boot” boot loader package. Summarised with great simplification, u-boot bundles device drivers, file systems, commands and a Bourne-like shell into a standalone package. Normally it auto-runs a script that brings up a system, but when used in interactive mode it allows a great deal of poking around.

U-Boot has his roots in embedded systems, where you have a nice 
environment to debug your system. You have already everything there to 
download files with s-record from serial, boot from tftp, etc.

Actually also setting up the memory controllers, timing, setting 
environment variables ...

This became so comfortable, that sometimes the U-Boot code is larger 
than the target system. So, after development is done, the system jumps 
into the real application or code ...

[TUHS] Re: Unix install & "standalone" package

[Warner Losh]

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On Mon, Sep 4, 2023 at 3:58 AM Paul Ruizendaal via TUHS <tuhs@tuhs.org>
wrote:

>
> Recently, I was looking into the “Das U-Boot” boot loader package.
> Summarised with great simplification, u-boot bundles device drivers, file
> systems, commands and a Bourne-like shell into a standalone package.
> Normally it auto-runs a script that brings up a system, but when used in
> interactive mode it allows a great deal of poking around.
>
> It made me think of the “standalone” set of programs for installing early
> Unix. On 16-bit understandably each basic command has to be a separate
> standalone program, but after the shift to 32-bit bundling more
> functionality in a single binary would have become possible.
>
> How did the Unix “standalone” package evolve in the 80’s, both in the
> research and BSD lineages? Is there any retrospective paper about that? Or
> is it a case of “Use the source, Luke”?
>

The stand package continued in research and BSD to be those programs needed
to install and/or recover
badly damaged systems.  You could create a new file system, copy a file
from the tape to a partition, etc.
You couldn't do general scripting with this, by and large.

Originally, they were tape programs. This made sense because of its
original focus. In time, some systems
could load the stand alone programs instead of the kernel, but they
continued the original focus.

This is, imho, due in large part due to the miniroot. The miniroot evolved
into both a full-enough system
to do the installation scripts in shell instead of C (Venix, at least, had
their install program written in C).
You'd copy the minroot to swap and then install the system. But a number of
additional programs were
placed into the miniroot so you could do some limited filesystem repair,
file editing, etc.

In addition, many vendor's ROMs grew in complexity. Solbourne's ROMs, for
example, could do basic
repair of UFS (clri level, not fsck level), and copy files from one place
to another. I often recovered a
Solbourne system I screwed up by attaching an external SCSI drive that had
a known good kernel,
init, etc.

The 'stand' environment was a whole set of tools that could be used to
build stand-alone programs that
shared much code of their full unix brethren, despite not having a full
kernel under them. Kernel services
were provided by different libraries that did filesystem things, block
driver things, network things, etc
in a similar way to Unix, but with a much reduced footprint.

initramfs, as has been mentioned elsewhere, is pretty much a Linux
invention. It was designed to
'punt' on the choose where to load things from and have a very minimal
interface between the boot
loader and the system. In time, it grew to support more interfaces, more
ways of loading, and better
ways to mount something that you could then 'pivot' onto. Few other unix
systems went this route, though
many adopted some variation on the pivot_root functionality. Linux has
moved beyond the pivot root after
having booted the correct kernel into being able to take over the machine
early in, say, UEFI startup with
a minimal kernel and initramfs that just knows how to load the next kernel.
They skipped the complex boot
loader stage, and went straight to the 'run linux earlier' stage which is
how things like LinuxBoot, coreboot
and others have put the boot logic into bash scripts. The ability to
'kexec' a kernel and replace the current
running kernel originated in the 'non-stop' world that wanted to reduce
downtime. Now, it's used to reduce
firmware complexity by eliminating large swaths of UEFI from the boot
process, but also generalizes in
the embedded space.

FreeBSD, from around FreeBSD 2 (1995 or so), had /rescue which largely took
over form the stand alone environment
for the repair duties of things. FreeBSD also adopted a more complex boot
loader that would load the
kernel, modules, set tunables, etc prior to kicking off the kernel. Between
/rescue having all the tools needed
to repair bad updates, repair failing disks, get that one last backup
before the drive is dead while you wait
for the new drive to be delivered, etc, and /boot/loader being able to
script loading the kernel while the BIOS
was still around so the need for drivers in the loader was lessened.
However, as the BIOS evolved into UEFI
and FreeBSD pushed into the embedded space whose firmware provided a less
rich environment to the boot
loader, so it was able to load things off fewer and fewer devices, it
became clear that it would need a pivot
root feature to allow it to boot all the way into FreeBSD, load some
drivers from an included ram disk, and then
use that mount a new root and then 'reroot' to that by killing everything
and running init from that new root.
FreeBSD also moved from Forth to Lua in its scripting language for the boot
loader, giving 'pre boot'
environment support better features. I also added the ability to use
FreeBSD boot loader as a Linux binary
to load FreeBSD and its metadata from a LinuxBoot environment. Finally,
FreeBSD has 'spun out' and
generalized the /rescue feature to allow creation of any 'BeastyBox'
environment, similar to what you get
in a busy box, or clone, environment. This environment, though, is meant in
large part on both Linux and
FreeBSD to be in constrained environments where a full install is
prohibitive (even those that never pivot
to something more, like ap, routers and nas boxes).

NetBSD retains many of the old BSD stand-alone programs that started on the
vax. I've not studied things
beyond noticing this. OpenBSD is similar. Their boot chain is a bit simpler
than FreeBSD's, though there's
noises about porting FreeBSD's boot there. There's a port of /boot/loader
to illumos too, but I don't know
if it is the default, or just available. So I'll not chat about it more.

So the original 'standalone' environment where you had one program running
on a system has evolved
into either a rich boot loader environment that lets one do a lot to decide
what kernel to load, or towards
having a minimal selection of unix programs faster and using /bin/sh or
similar to do scripting. These
reduced environments are often called standalone, though all they share
just the name with the earlier
'stand' programs: they are full unix programs, but with reduced feature
sets and 'linker magic' to package
them in a way that's faster, smaller, etc (eg all in one binary). FreeBSD's
boot loader is an outgrowth
of the original standalone env, by way of a port of NetBSD's libsa.

I suspect in the future, we'll see more and more of a trend for low-level
init and then handing off to some
built-in kernel (be it Linux, BSD-based (there's now kexec), or whatever)
to reuse more of the vetted code
rather than re-inventing Unix inside the boot loader (which is a valid
criticism of FreeBSD's boot loader,
though it's rich feature set is what you get for the complexity).

Does that answer the prompt? Should I try to make this into more of a
retrospective paper and actually
do the research on the areas I was hand-wavy about?

Warner

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[TUHS] Re: Unix install & "standalone" package

[Dan Cross]

On Mon, Sep 4, 2023 at 1:08 PM Warner Losh <imp@bsdimp.com> wrote:
> [snip]
> There's a port of /boot/loader to illumos too, but I don't know
> if it is the default, or just available. So I'll not chat about it more.

I can confirm that it is the default on i86pc, though not universally.
At Oxide, for example, we boot directly into a very small loader held
in flash that has a compressed cpio archive containing the kernel and
a few necessary kernel modules compiled into it (as a byte blob); we
uncompress that blob into physical memory, locate and load the kernel
like a normal ELF binary, and jump to the kernel's ELF entry point,
passing a few basic arguments (notably, the location and length of the
cpio archive in physical memory). Entry to the kernel is thus in
64-bit mode with paging enabled.

> So the original 'standalone' environment where you had one program running on a system has evolved
> into either a rich boot loader environment that lets one do a lot to decide what kernel to load, or towards
> having a minimal selection of unix programs faster and using /bin/sh or similar to do scripting. These
> reduced environments are often called standalone, though all they share just the name with the earlier
> 'stand' programs: they are full unix programs, but with reduced feature sets and 'linker magic' to package
> them in a way that's faster, smaller, etc (eg all in one binary). FreeBSD's boot loader is an outgrowth
> of the original standalone env, by way of a port of NetBSD's libsa.
>
> I suspect in the future, we'll see more and more of a trend for low-level init and then handing off to some
> built-in kernel (be it Linux, BSD-based (there's now kexec), or whatever) to reuse more of the vetted code
> rather than re-inventing Unix inside the boot loader (which is a valid criticism of FreeBSD's boot loader,
> though it's rich feature set is what you get for the complexity).
>
> Does that answer the prompt? Should I try to make this into more of a retrospective paper and actually
> do the research on the areas I was hand-wavy about?

That would be interesting.

I can still remember booting IBM 6150 RTs into a miniroot environment
and using that to create and initialize filesystems when installing
AOS (4.3BSD for the RT) back in the day. To my mind, the standalone
programs were always oriented towards solving the related problems of
bootstrap initialization onto a fresh machine, and disaster recovery
when things were really, really messed up.

As I recall, the RT miniroot could either load from tape, or one could
`dd` it into swap and boot from that. In either case, I seem to recall
it was copied into memory and run as a RAM disk. The idea of busy-box
like "a bunch of utilities compiled into the same binary" was to save
space, particularly since this would be copied into RAM; even with
demand paging, redundant copies of bits from `libc` in each binary
were a waste for what was intended to be a minimal environment anyway.

        - Dan C.

[TUHS] Re: Unix install & "standalone" package

[Paul Ruizendaal via TUHS]

> Does that answer the prompt? Should I try to make this into more of a retrospective paper and actually
> do the research on the areas I was hand-wavy about?

That certainly answered the prompt, much appreciated the walkthrough. Currently just trying to get a view of the field and to collect recollections on how it was done back in the day.

Part of it is finding a conceptual framework that can make sense of it all.

One pitfall I would like to avoid in my own thinking is conflating “installing” and “booting”, even though the two seem related (one loads bits into permanent storage, the other into volatile storage; both are built around incrementally adding capability). When variable hardware comes into play, the two mix even more. Also related is the topic of recovery.

The starting point seems to be a setup where a small set of standalone programs is used to load or repair the bits, as was done for 16-bit unix.

A next conceptual step seems to be where first a very basic system is installed that is then used for further installation or for repair. This step seems to have come early, if this 32V install page is reflective of how it was done back in 1980: https://gunkies.org/wiki/Installing_32V_on_SIMH  The idea to use disk swap space for this also seems to have come early (and I suppose the concept lives on in “rescue partitions”).

Another conceptual step might be where early installer phases run a different, smaller kernel (or even OS) than the one being installed. There seems to be much potential for a “wheel of reincarnation” here where as an installer grows large, a pre-installer is created to load the installer and then the pre-installer grows large, etc. For booting, this wheel seems to have turned about 5 times in current Linux. Installing that from scratch on a fully blank SBC (without prepping a removable disk on another computer) also appears to have 4 or 5 revolutions. That is one revolution every 5 years for the 25 years from the late seventies to the early 2000’s.

Then there is the question of where in the "installer stack" to stop. My current interest excludes (precursors to) package managers, containers, etc.

In short: much to ponder, thanks to all for sharing recollections.


> On 4 Sep 2023, at 19:07, Warner Losh <imp@bsdimp.com> wrote:
> 
> 
> 
> On Mon, Sep 4, 2023 at 3:58 AM Paul Ruizendaal via TUHS <tuhs@tuhs.org> wrote:
> 
> Recently, I was looking into the “Das U-Boot” boot loader package. Summarised with great simplification, u-boot bundles device drivers, file systems, commands and a Bourne-like shell into a standalone package. Normally it auto-runs a script that brings up a system, but when used in interactive mode it allows a great deal of poking around.
> 
> It made me think of the “standalone” set of programs for installing early Unix. On 16-bit understandably each basic command has to be a separate standalone program, but after the shift to 32-bit bundling more functionality in a single binary would have become possible.
> 
> How did the Unix “standalone” package evolve in the 80’s, both in the research and BSD lineages? Is there any retrospective paper about that? Or is it a case of “Use the source, Luke”?
> 
> The stand package continued in research and BSD to be those programs needed to install and/or recover
> badly damaged systems.  You could create a new file system, copy a file from the tape to a partition, etc.
> You couldn't do general scripting with this, by and large.
> 
> Originally, they were tape programs. This made sense because of its original focus. In time, some systems
> could load the stand alone programs instead of the kernel, but they continued the original focus.
> 
> This is, imho, due in large part due to the miniroot. The miniroot evolved into both a full-enough system
> to do the installation scripts in shell instead of C (Venix, at least, had their install program written in C).
> You'd copy the minroot to swap and then install the system. But a number of additional programs were
> placed into the miniroot so you could do some limited filesystem repair, file editing, etc.
> 
> In addition, many vendor's ROMs grew in complexity. Solbourne's ROMs, for example, could do basic
> repair of UFS (clri level, not fsck level), and copy files from one place to another. I often recovered a
> Solbourne system I screwed up by attaching an external SCSI drive that had a known good kernel,
> init, etc.
> 
> The 'stand' environment was a whole set of tools that could be used to build stand-alone programs that
> shared much code of their full unix brethren, despite not having a full kernel under them. Kernel services
> were provided by different libraries that did filesystem things, block driver things, network things, etc
> in a similar way to Unix, but with a much reduced footprint.
> 
> initramfs, as has been mentioned elsewhere, is pretty much a Linux invention. It was designed to
> 'punt' on the choose where to load things from and have a very minimal interface between the boot
> loader and the system. In time, it grew to support more interfaces, more ways of loading, and better
> ways to mount something that you could then 'pivot' onto. Few other unix systems went this route, though
> many adopted some variation on the pivot_root functionality. Linux has moved beyond the pivot root after
> having booted the correct kernel into being able to take over the machine early in, say, UEFI startup with
> a minimal kernel and initramfs that just knows how to load the next kernel. They skipped the complex boot
> loader stage, and went straight to the 'run linux earlier' stage which is how things like LinuxBoot, coreboot
> and others have put the boot logic into bash scripts. The ability to 'kexec' a kernel and replace the current
> running kernel originated in the 'non-stop' world that wanted to reduce downtime. Now, it's used to reduce
> firmware complexity by eliminating large swaths of UEFI from the boot process, but also generalizes in
> the embedded space.
> 
> FreeBSD, from around FreeBSD 2 (1995 or so), had /rescue which largely took over form the stand alone environment
> for the repair duties of things. FreeBSD also adopted a more complex boot loader that would load the
> kernel, modules, set tunables, etc prior to kicking off the kernel. Between /rescue having all the tools needed
> to repair bad updates, repair failing disks, get that one last backup before the drive is dead while you wait
> for the new drive to be delivered, etc, and /boot/loader being able to script loading the kernel while the BIOS
> was still around so the need for drivers in the loader was lessened. However, as the BIOS evolved into UEFI
> and FreeBSD pushed into the embedded space whose firmware provided a less rich environment to the boot
> loader, so it was able to load things off fewer and fewer devices, it became clear that it would need a pivot
> root feature to allow it to boot all the way into FreeBSD, load some drivers from an included ram disk, and then
> use that mount a new root and then 'reroot' to that by killing everything and running init from that new root.
> FreeBSD also moved from Forth to Lua in its scripting language for the boot loader, giving 'pre boot'
> environment support better features. I also added the ability to use FreeBSD boot loader as a Linux binary
> to load FreeBSD and its metadata from a LinuxBoot environment. Finally, FreeBSD has 'spun out' and
> generalized the /rescue feature to allow creation of any 'BeastyBox' environment, similar to what you get
> in a busy box, or clone, environment. This environment, though, is meant in large part on both Linux and
> FreeBSD to be in constrained environments where a full install is prohibitive (even those that never pivot
> to something more, like ap, routers and nas boxes).
> 
> NetBSD retains many of the old BSD stand-alone programs that started on the vax. I've not studied things
> beyond noticing this. OpenBSD is similar. Their boot chain is a bit simpler than FreeBSD's, though there's
> noises about porting FreeBSD's boot there. There's a port of /boot/loader to illumos too, but I don't know
> if it is the default, or just available. So I'll not chat about it more.
> 
> So the original 'standalone' environment where you had one program running on a system has evolved
> into either a rich boot loader environment that lets one do a lot to decide what kernel to load, or towards
> having a minimal selection of unix programs faster and using /bin/sh or similar to do scripting. These
> reduced environments are often called standalone, though all they share just the name with the earlier
> 'stand' programs: they are full unix programs, but with reduced feature sets and 'linker magic' to package
> them in a way that's faster, smaller, etc (eg all in one binary). FreeBSD's boot loader is an outgrowth
> of the original standalone env, by way of a port of NetBSD's libsa. 
> 
> I suspect in the future, we'll see more and more of a trend for low-level init and then handing off to some
> built-in kernel (be it Linux, BSD-based (there's now kexec), or whatever) to reuse more of the vetted code
> rather than re-inventing Unix inside the boot loader (which is a valid criticism of FreeBSD's boot loader,
> though it's rich feature set is what you get for the complexity).
> 
> Does that answer the prompt? Should I try to make this into more of a retrospective paper and actually
> do the research on the areas I was hand-wavy about?
> 
> Warner

[TUHS] Re: Unix install & "standalone" package

[Clem Cole]

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below..

On Tue, Sep 5, 2023 at 7:16 AM Paul Ruizendaal via TUHS <tuhs@tuhs.org>
wrote:

> One pitfall I would like to avoid in my own thinking is conflating
> “installing” and “booting”,
>
That is an excellent point.  I think that the real question comes back to
how 'cold' the 'system' is.

Booting is the process of making the processor 'live' including the loading
of the 'initial memory contents' (IBM used to call it IPL for
Initial Program Load), while 'installation' is setting up a 'system' which
'lives' in the peripherals as long-term storage.  When you 'Power-On' a
CPU, you often need to IPL a system even if the peripherals have been set
up [back in the day of core memory, you might not even have that as the OS
was not lost when power was removed].


> The starting point seems to be a setup where a small set of standalone
> programs is used to load or repair the bits, as was done for 16-bit unix.
>
You are solving the 'chicken and egg' issue.  Truth is Ken's famous
"Reflections on Trusting Trust"  comes to bear here.   The fact is you are
'setting up' (or restoring) a system for bits that were generated on
another. The critical point is that you are setting the initial 'systems'
bits into the peripherals for that specific system.   You are relying on
making copies of those bits from another system.  The question is how to
get them into the new media.

All the standalone system is doing is offering you a minimum way of making
a copy of that other system without having access to its hardware directly.



> A next conceptual step seems to be where first a very basic system is
> installed that is then used for further installation or for repair. This
> step seems to have come early, if this 32V install page is reflective of
> how it was done back in 1980:
> https://gunkies.org/wiki/Installing_32V_on_SIMH  The idea to use disk
> swap space for this also seems to have come early (and I suppose the
> concept lives on in “rescue partitions”).
>

Newer versions of the system setup scheme offer more and more features, as
the options of how you set up might be different from the origin system
become greater and greater. Modern OS implementations of the Unix
technologies now run on a much more comprehensive range of devices, and
frankly, 'IPL' much less might be set up from so many different types of
sources, it's not surprising that the IPL schemes and the system setup
scheme are a lot more sophisticated.
But remember, when you examine the past scheme, you must also consider the
constraints of the timeframe (particularly the economics of certain
choices).  It's not that you could not have built something like some of
today's schemes — it was expensive with respect to what was available and,
frankly, not wholly necessary.



>
> Another conceptual step might be where early installer phases run a
> different, smaller kernel (or even OS) than the one being installed. There
> seems to be much potential for a “wheel of reincarnation” here where as an
> installer grows large, a pre-installer is created to load the installer and
> then the pre-installer grows large, etc. For booting, this wheel seems to
> have turned about 5 times in current Linux. Installing that from scratch on
> a fully blank SBC (without prepping a removable disk on another computer)
> also appears to have 4 or 5 revolutions. That is one revolution every 5
> years for the 25 years from the late seventies to the early 2000’s.
>

The circle started long before that.  For instance, the boot/IPL got more
flexible (like Sam's autoconfiguration work developed for VAX).   Why?
Because the HW configurations had begun to branch and get bushy.  Even with
the PDP-11's peripheral set in V7, it was getting more complex.   But
those kernel
configurations were statically linked.  Sun added dynamic linking, making
both IPL, much less setup/installation more complex.   But frankly, to do
that on an earlier machine took a lot of work.   BSD2.9 did backport much
of the VAX work but not all of it.  It was often too difficult, and the
'gain' for the effort was low.

So my modern UNIX implementations, be it macOS, *BSD, or the Linux family,
the schemes have matured and been recreated over and over.  For instance,
you can look at what Apple's done with its system install scheme.   It
hides the setup/tear down as of the root and then makes a read-only root
system under the covers.   This is both a blessing and a curse.  Sure, it
helps make things a lot more secure for them and basic users, but that
choice breaks traditional admin scripts [which drives me nuts think -
/etc/periodic] because the new Apple system implementors don't understand
why the core system works the way it does and thus those of us that have
scripts have worked since V7 in the late 1970s, now don't.

Clem
ᐧ

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[TUHS] Re: Unix install & "standalone" package

[Warner Losh]

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On Tue, Sep 5, 2023 at 5:15 AM Paul Ruizendaal <pnr@planet.nl> wrote:

> > Does that answer the prompt? Should I try to make this into more of a
> retrospective paper and actually
> > do the research on the areas I was hand-wavy about?
>
> That certainly answered the prompt, much appreciated the walkthrough.
> Currently just trying to get a view of the field and to collect
> recollections on how it was done back in the day.
>
> Part of it is finding a conceptual framework that can make sense of it all.
>

Yes. V7 and other early unix had a 'stand alone' framework. So that's one
piece of the puzzle. It could be used for anything (I've seen private
diagnostic stand alone programs at Solbourne that would do more extensive
tests than the boot roms did for RMA and manufacturing line acceptance).
But as they come down to us from AT&T, they are just the bits needed to
install a system from scratch (or in some cases fix a system by booting the
distribution tapes).


> One pitfall I would like to avoid in my own thinking is conflating
> “installing” and “booting”, even though the two seem related (one loads
> bits into permanent storage, the other into volatile storage; both are
> built around incrementally adding capability). When variable hardware comes
> into play, the two mix even more. Also related is the topic of recovery.
>

There's "booting" and then there's "bootstrapping". booting happens all the
time, but installation happens rarely. The problem is that the install
process for V7 and earlier systems was to load a series of programs into
memory from tape that did each step of the process to stay within the 64k
limits imposed by the platform. That process was done by a series of
standalone programs that could, in some cases, act as system repair for
certain cases of 'afu' system.


> The starting point seems to be a setup where a small set of standalone
> programs is used to load or repair the bits, as was done for 16-bit unix.
>

Yea, that's where stand came from originally: An environment that could run
a limited program w/o booting the kernel...


> A next conceptual step seems to be where first a very basic system is
> installed that is then used for further installation or for repair. This
> step seems to have come early, if this 32V install page is reflective of
> how it was done back in 1980:
> https://gunkies.org/wiki/Installing_32V_on_SIMH  The idea to use disk
> swap space for this also seems to have come early (and I suppose the
> concept lives on in “rescue partitions”).
>

Yes. It was quite common for the next step to be when demand paging became
a thing. Once demand paging became a thing and you didn't need a dedicated
swap partition, you could 'borrow' the installed system's swap partition
(or what would become the installed system's swap partition) to have a
richer set of tools. This would use otherwise wasted space for the install,
then you'd overwrite it with whatever workload you put on your system.


> Another conceptual step might be where early installer phases run a
> different, smaller kernel (or even OS) than the one being installed. There
> seems to be much potential for a “wheel of reincarnation” here where as an
> installer grows large, a pre-installer is created to load the installer and
> then the pre-installer grows large, etc. For booting, this wheel seems to
> have turned about 5 times in current Linux. Installing that from scratch on
> a fully blank SBC (without prepping a removable disk on another computer)
> also appears to have 4 or 5 revolutions. That is one revolution every 5
> years for the 25 years from the late seventies to the early 2000’s.
>

Indeed, the whole linuxboot saga where you boot a minimal linux kernel that
has a shell script (or similar) that decides where to load the complete
kernel from is also interesting (doubly so to me because it means I can
sneak in at that point and load FreeBSD onto the system).


> Then there is the question of where in the "installer stack" to stop. My
> current interest excludes (precursors to) package managers, containers, etc.
>

Yes. For me, the 'preboot environment' is a better mental framework to look
at it with. Or 'pre-kernel' or 'non-kernel' environments. Though that
paradigm runs out of steam in the 90s when people started booting kernels
with bundled ram disks (in various flavors) to do the installation to allow
boot medium to be used to load additional data (eg the system). The
read/write nature of RAM made this vector useful, even when CDROMs appeared
on the scene. It was easier to run off a ram disk than off the CDROM
because you don't have to have symlinks to a (small) RAM disks for the bits
of the system that needed to be read/write during the install process...

The 'standalone' stuff, as typified by the src/stand directory, was all
pre-kernel or non-kernel use-cases. Sometimes it was used to build a bit of
code that had to be small, but was also used to build code to load the
kernel (even dating back to the original boot loader for V7, though I'm
relying on my memory which may be confusing that with the 2BSD
bootstrap)... The stuff that was 'standalone-but-on-a-unix-kernel' came
later.

It might also be amusing to note: I once contemplated porting V7 unix to
replace FreeBSD's stand environment to replace the various ad-hock hacks
that had grown up. But I found that those hacks were smaller in the end,
and needed less code space to support more things (excluding crypto and
compression) than the V7 did once you started looking at modifying it to
support multiple filesystem types, adding a network stack etc. While V7 is
nice and clean, it's also immature in terms of features needed for a modern
loader...

Warner


> In short: much to ponder, thanks to all for sharing recollections.
>
>
> > On 4 Sep 2023, at 19:07, Warner Losh <imp@bsdimp.com> wrote:
> >
> >
> >
> > On Mon, Sep 4, 2023 at 3:58 AM Paul Ruizendaal via TUHS <tuhs@tuhs.org>
> wrote:
> >
> > Recently, I was looking into the “Das U-Boot” boot loader package.
> Summarised with great simplification, u-boot bundles device drivers, file
> systems, commands and a Bourne-like shell into a standalone package.
> Normally it auto-runs a script that brings up a system, but when used in
> interactive mode it allows a great deal of poking around.
> >
> > It made me think of the “standalone” set of programs for installing
> early Unix. On 16-bit understandably each basic command has to be a
> separate standalone program, but after the shift to 32-bit bundling more
> functionality in a single binary would have become possible.
> >
> > How did the Unix “standalone” package evolve in the 80’s, both in the
> research and BSD lineages? Is there any retrospective paper about that? Or
> is it a case of “Use the source, Luke”?
> >
> > The stand package continued in research and BSD to be those programs
> needed to install and/or recover
> > badly damaged systems.  You could create a new file system, copy a file
> from the tape to a partition, etc.
> > You couldn't do general scripting with this, by and large.
> >
> > Originally, they were tape programs. This made sense because of its
> original focus. In time, some systems
> > could load the stand alone programs instead of the kernel, but they
> continued the original focus.
> >
> > This is, imho, due in large part due to the miniroot. The miniroot
> evolved into both a full-enough system
> > to do the installation scripts in shell instead of C (Venix, at least,
> had their install program written in C).
> > You'd copy the minroot to swap and then install the system. But a number
> of additional programs were
> > placed into the miniroot so you could do some limited filesystem repair,
> file editing, etc.
> >
> > In addition, many vendor's ROMs grew in complexity. Solbourne's ROMs,
> for example, could do basic
> > repair of UFS (clri level, not fsck level), and copy files from one
> place to another. I often recovered a
> > Solbourne system I screwed up by attaching an external SCSI drive that
> had a known good kernel,
> > init, etc.
> >
> > The 'stand' environment was a whole set of tools that could be used to
> build stand-alone programs that
> > shared much code of their full unix brethren, despite not having a full
> kernel under them. Kernel services
> > were provided by different libraries that did filesystem things, block
> driver things, network things, etc
> > in a similar way to Unix, but with a much reduced footprint.
> >
> > initramfs, as has been mentioned elsewhere, is pretty much a Linux
> invention. It was designed to
> > 'punt' on the choose where to load things from and have a very minimal
> interface between the boot
> > loader and the system. In time, it grew to support more interfaces, more
> ways of loading, and better
> > ways to mount something that you could then 'pivot' onto. Few other unix
> systems went this route, though
> > many adopted some variation on the pivot_root functionality. Linux has
> moved beyond the pivot root after
> > having booted the correct kernel into being able to take over the
> machine early in, say, UEFI startup with
> > a minimal kernel and initramfs that just knows how to load the next
> kernel. They skipped the complex boot
> > loader stage, and went straight to the 'run linux earlier' stage which
> is how things like LinuxBoot, coreboot
> > and others have put the boot logic into bash scripts. The ability to
> 'kexec' a kernel and replace the current
> > running kernel originated in the 'non-stop' world that wanted to reduce
> downtime. Now, it's used to reduce
> > firmware complexity by eliminating large swaths of UEFI from the boot
> process, but also generalizes in
> > the embedded space.
> >
> > FreeBSD, from around FreeBSD 2 (1995 or so), had /rescue which largely
> took over form the stand alone environment
> > for the repair duties of things. FreeBSD also adopted a more complex
> boot loader that would load the
> > kernel, modules, set tunables, etc prior to kicking off the kernel.
> Between /rescue having all the tools needed
> > to repair bad updates, repair failing disks, get that one last backup
> before the drive is dead while you wait
> > for the new drive to be delivered, etc, and /boot/loader being able to
> script loading the kernel while the BIOS
> > was still around so the need for drivers in the loader was lessened.
> However, as the BIOS evolved into UEFI
> > and FreeBSD pushed into the embedded space whose firmware provided a
> less rich environment to the boot
> > loader, so it was able to load things off fewer and fewer devices, it
> became clear that it would need a pivot
> > root feature to allow it to boot all the way into FreeBSD, load some
> drivers from an included ram disk, and then
> > use that mount a new root and then 'reroot' to that by killing
> everything and running init from that new root.
> > FreeBSD also moved from Forth to Lua in its scripting language for the
> boot loader, giving 'pre boot'
> > environment support better features. I also added the ability to use
> FreeBSD boot loader as a Linux binary
> > to load FreeBSD and its metadata from a LinuxBoot environment. Finally,
> FreeBSD has 'spun out' and
> > generalized the /rescue feature to allow creation of any 'BeastyBox'
> environment, similar to what you get
> > in a busy box, or clone, environment. This environment, though, is meant
> in large part on both Linux and
> > FreeBSD to be in constrained environments where a full install is
> prohibitive (even those that never pivot
> > to something more, like ap, routers and nas boxes).
> >
> > NetBSD retains many of the old BSD stand-alone programs that started on
> the vax. I've not studied things
> > beyond noticing this. OpenBSD is similar. Their boot chain is a bit
> simpler than FreeBSD's, though there's
> > noises about porting FreeBSD's boot there. There's a port of
> /boot/loader to illumos too, but I don't know
> > if it is the default, or just available. So I'll not chat about it more.
> >
> > So the original 'standalone' environment where you had one program
> running on a system has evolved
> > into either a rich boot loader environment that lets one do a lot to
> decide what kernel to load, or towards
> > having a minimal selection of unix programs faster and using /bin/sh or
> similar to do scripting. These
> > reduced environments are often called standalone, though all they share
> just the name with the earlier
> > 'stand' programs: they are full unix programs, but with reduced feature
> sets and 'linker magic' to package
> > them in a way that's faster, smaller, etc (eg all in one binary).
> FreeBSD's boot loader is an outgrowth
> > of the original standalone env, by way of a port of NetBSD's libsa.
> >
> > I suspect in the future, we'll see more and more of a trend for
> low-level init and then handing off to some
> > built-in kernel (be it Linux, BSD-based (there's now kexec), or
> whatever) to reuse more of the vetted code
> > rather than re-inventing Unix inside the boot loader (which is a valid
> criticism of FreeBSD's boot loader,
> > though it's rich feature set is what you get for the complexity).
> >
> > Does that answer the prompt? Should I try to make this into more of a
> retrospective paper and actually
> > do the research on the areas I was hand-wavy about?
> >
> > Warner
>
>

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[TUHS] Unix install & "standalone" package

[Norman Wilson]

I don't remember any special many-programs-in-one binary
like busybox in any Unix from the days when Unix was simple
enough for me to understand.  That covers the entire lifetime
of the Research systems, but also System V and the BSDs and
their sundry offspring up into at least the 1990s.

I'm pretty sure OpenBSD at least still has nothing like
busybox.  The nearest thing was to make sure certain programs
were linked statically (or existed in alternate statically-
linked versions) so they would work before shared libraries
were available.  (It seems to be common wisdom that `sbin'
means `system bin' these days, but I remember once, long ago,
being told it stood for `static bin'.)

Perhaps the question to ask is why such a magic program is
needed at all.  Is it just because programs like the shell
have become so large and unwieldy that they won't fit in
a small environment suitable for loading into an initramfs?

Older UNIXes, even on the VAX, didn't use an initramfs.
the boot code had just enough understanding of devices and
file systems to load the kernel and to point it at the
real root file system.  The VAX hardware designers had
a clever scheme on many (but, strangely, not all) VAX
variants by which the hardware had several little boot
ROMs, each containing a bare-bones read-only device
driver for a particular device along with a few
instructions to read the first sector into memory
and start it, with pointers to the boot-rom driver
and device ID in specified registers.  That was enough
to support a device-independent Unix boot block that
could read unix (or another file name typed on the
console) from the root of the file system at the start
of the disk.  I know it was because I wrote such a
boot block, though I don't know whether anyone else
did.  (Other systems, I think, just used it to load
/boot, a larger and more-capable program.)

Maybe it was just that the boot environment was simpler
in older systems, without the need to load kernel modules
or support multiple locations and means of access for
the root?

Norman Wilson
Toronto ON