problem with compressing the kernel

Hi, everyone,
The linux kernel is compressed into a zip file, which is done under linux
using the utility
named gzip. now, I am doing such work under Windows NT. I  am wondering if
there is
a utility that can do the same job , compressing the linux kernel ,which
still can be
uncompressed at running time.
Thanks a lot.

Rolf Liu
Phone: 86-10-65642023            Fax: 86-10-65668458
-----------------------------------------------------------------


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Hi, everyone,
The linux kernel is compressed into a zip file, which is done under linux
using the utility
named gzip.

and thus a gzip file not a zip file, but this is being picky

now, I am doing such work under Windows NT. I  am wondering if
there is
a utility that can do the same job , compressing the linux kernel ,which
still can be
uncompressed at running time.

well my initial thought is why would you need this?

the answer is no.

you seem to be confused anyway, yes the kernel is compressed for x86
machiens (it is however not compressed for other architectures, my ppc
box uses a normal uncompresased vmlinux image.

however it is not just a compressed gzip file

using the file tool a gzip file will look like

[16:06:53] 23 sjhmmj sjh ~>file
/home/asd/sources/pmac/linux-pmac-2.2.15-pre14.tar.gz
/home/asd/sources/pmac/linux-pmac-2.2.15-pre14.tar.gz: gzip compressed
data, deflated, last modified: Mon Mar 27 01:27:14 2000, os: Unix

wheras a kernel image (for ppc) will look like

[17:18:53] 1 innuendo sjh ~>file /mac/System\ Folder/Linux\
Kernels/vmlinux-2.2.15pre14
/mac/System Folder/Linux Kernels/vmlinux-2.2.15pre14: ELF 32-bit MSB
executable, PowerPC or cisco 4500, version 1, statically linked, not
stripped

which is a plain all ordinary elf binary pretty much

the compressed kernels found on x86 boxes will look like
[15:56:34] 22 sjhmmj sjh ~>file /boot/devel
/boot/devel: Linux kernel x86 boot executable bzImage, version 2.2.16
(sjh@sjhmmj) #46 SMP Thu, RO-rootFS, root_dev=0x301, Normal VGA

it may seem you can just gzip an uncompressed vmlinux and get a vmlinuz
that will boot, except if you notice the devel image just there is not a
gzip file. There is some executable code added on the front of the image
so the x86 box will run it on boot up, some of this code uncompresses
the image.

So although gzip is available on windows (see prep.ai.mit.edu or the
cygwin site for more details (www.cygnus.com will have links)) it will
not help making a kernel image.

Now of course I wonder why you would need the ability as after all a
linux box is all you need to compile and make the image, or heck a
compatible gcc on any unix can in theory compile the kernel, the utility
to compress and uncompress the kernel is in the source tree so long as
you can compile the source tree it should work fine. gzip is not listed
as a requirement in kernel compiling in the file
/usr/src/linux/Documentation/Changes for this reason, if you can compile
the kernel on a machine it can create the compressed images if needed.

And of course remember you dont need otr use compressed images on ppc
machines.

	See You
	    Steve

--
sjh@wibble.net http://wibble.net/~sjh/
Look Up In The Sky
   Is it a bird?  No
      Is it a plane?  No
         Is it a small blue banana?
YES

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On Wed, 28 Jun 2000, Steven Hanley wrote:

you seem to be confused anyway, yes the kernel is compressed for x86
machiens (it is however not compressed for other architectures, my ppc
box uses a normal uncompresased vmlinux image.

Perhaps on a Mac, but _all_ the kernels I have ever built for _all_ my PPC
machines have _always_ been compressed, without a _single_ exception.
Browsing the tree you'll easily find that there the kernel image is
compressed (maybe depending on some CONFIG option) on:

- alpha
- arm
- i386
- m68k
- ppc

so please don't claim that it is x86 specific without checking the facts
first.

Now of course I wonder why you would need the ability as after all a
linux box is all you need to compile and make the image, or heck a
compatible gcc on any unix can in theory compile the kernel, the utility
to compress and uncompress the kernel is in the source tree so long as
you can compile the source tree it should work fine. gzip is not listed
as a requirement in kernel compiling in the file
/usr/src/linux/Documentation/Changes for this reason, if you can compile
the kernel on a machine it can create the compressed images if needed.

This looks more like a documentation error. Nowadays you can get your
sources with bzip2, but for very long gzip/gunzip was an implicit
prerequisite to uncompress the kernel tarball (and the patches), otherwise
you could not even have a look at the requirements. Chicken and egg...

And of course remember you dont need otr use compressed images on ppc
machines.

I do need them. Not all PPC machines are macs, it seems :-)

	Regards,
	Gabriel.


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in response to a few other people, yes I realise you may wish to use
compressed images on non x86 and that it is poossible. Thankyou for
further claryfying some details about the process though. (embedded
machiens hadnt crossed my mind for example)

Gabriel Paubert wrote:

machines have _always_ been compressed, without a _single_ exception.
Browsing the tree you'll easily find that there the kernel image is
compressed (maybe depending on some CONFIG option) on:

- alpha
- arm
- i386
- m68k
- ppc

well it is how you build them really, you probably type make zImage or
make bzImage or some such, I personally just type make vmlinux for my
ppc kernels as I dont need the compressed kernel so dont use it.

the output is dictated by the command you use to make the kernel, and
the setup in the makefile.

so please don't claim that it is x86 specific without checking the facts
first.

it is specific in that x86 is braindead enough that for years the option
was necessary, I am unsure if x86 still needs the compressed image
(anyone?) however as has been pointed out you may use compressed images
on other architectures. I still strongly suspect the person asking on a
ppc list how to compress a kernel for linux on an NT box was somewhat
confused at least.

This looks more like a documentation error. Nowadays you can get your
sources with bzip2, but for very long gzip/gunzip was an implicit
prerequisite to uncompress the kernel tarball (and the patches), otherwise
you could not even have a look at the requirements. Chicken and egg...

not at all, this list is in the kernel tree, it has nothing to do with
what format you get your kernel in, (rsync or cvs are common, you may
notice, as examples of retrival of both patch updates and full kernel
updates that have no need of gzip (ignoring that both can have and
commonly do have, zlib compiled in and use it during transfer) the
Changes file lists what utilities/tools are needed to actually compile
the kernel. There is no need for bzip2 or gzip in the compilation
process.

quoted

And of course remember you dont need otr use compressed images on ppc
machines.

I do need them. Not all PPC machines are macs, it seems :-)

well if the hardware is embedded or similarly lacking in space as
someone suggested I can understand the need, or possible x86. Otherwise
I would be surprised if the hardware cant handle large images. There is
a difference between "need" and "common use"

        Regards,
        Gabriel.

	See You
	    Steve

--
sjh@wibble.net http://wibble.net/~sjh/
Look Up In The Sky
   Is it a bird?  No
      Is it a plane?  No
         Is it a small blue banana?
YES

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At 4:05 AM -0500 6/28/2000, Gabriel Paubert wrote:

On Wed, 28 Jun 2000, Steven Hanley wrote:

quoted

you seem to be confused anyway, yes the kernel is compressed for x86
machiens (it is however not compressed for other architectures, my ppc
box uses a normal uncompresased vmlinux image.

Perhaps on a Mac, but _all_ the kernels I have ever built for _all_ my PPC
machines have _always_ been compressed, without a _single_ exception.
Browsing the tree you'll easily find that there the kernel image is
compressed (maybe depending on some CONFIG option) on:

- alpha
- arm
- i386
- m68k
- ppc

Just to confuse the issue a bit, I'd like to note that on Mac68k (maybe
m68k in general, I don't recall), you *can* take an uncompressed kernel
image, run it through gzip or bzip2, and boot with it. Sometimes always
needing a seperate bootloader can be a luxury. :)


Cheers - Tony :)


--
Tony Mantler       Renaissance Nerd Extraordinaire     nicoya@apia.dhs.org
Winnipeg, Manitoba, Canada                     http://nicoya.feline.pp.se/


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On Wed, 28 Jun 2000, Steven Hanley wrote:

the output is dictated by the command you use to make the kernel, and
the setup in the makefile.

Indeed.

quoted

so please don't claim that it is x86 specific without checking the facts
first.

it is specific in that x86 is braindead enough that for years the option
was necessary, I am unsure if x86 still needs the compressed image
(anyone?) however as has been pointed out you may use compressed images
on other architectures. I still strongly suspect the person asking on a
ppc list how to compress a kernel for linux on an NT box was somewhat
confused at least.

Try to build a ppc boot floppy without compression (of for any achitecture
if you have enough drivers).

quoted

This looks more like a documentation error. Nowadays you can get your
sources with bzip2, but for very long gzip/gunzip was an implicit
prerequisite to uncompress the kernel tarball (and the patches), otherwise
you could not even have a look at the requirements. Chicken and egg...

not at all, this list is in the kernel tree, it has nothing to do with
what format you get your kernel in, (rsync or cvs are common, you may
notice, as examples of retrival of both patch updates and full kernel
updates that have no need of gzip (ignoring that both can have and
commonly do have, zlib compiled in and use it during transfer) the
Changes file lists what utilities/tools are needed to actually compile
the kernel. There is no need for bzip2 or gzip in the compilation
process.

Not in the compilation, but since when do you use
cvs/rsync/bitkeeper/whatever ?

The official source tree (the mirrors of ftp.kernel.org) is still only
available as gz and more recently with bz2. So historically gzip has been
a prerequisite to look at the kernel source and build your kernel, that's
all what I claimed (did you use Linux and build your kernels from
ftp.funet.fi in 1995 ?).

For my needs I only use ftp.kernel.org kernels with my own patches since I
was severely burnt the day vger cvs disappeared, but that's clearly a
personal choice (simply that I don't trust anything else anymore).

quoted

quoted

And of course remember you dont need otr use compressed images on ppc
machines.

I do need them. Not all PPC machines are macs, it seems :-)

well if the hardware is embedded or similarly lacking in space as
someone suggested I can understand the need, or possible x86. Otherwise
I would be surprised if the hardware cant handle large images. There is
a difference between "need" and "common use"

The HW/FW I have can handle fairly large images (several Mb at least),
floppies may have trouble however and I prefer to transfer smaller images
for network loads (besides the fact that the raw vmlinux will never boot
on my machines, I need to setup the HW through a first stage loader in a
way the kernel likes before giving it control).

That's common use BTW, there are probably more PPC processors running
Linux in embedded environments than in PowerMacs. Besides that, you
claimed that "you don't need to use compressed images on PPC machines"
which is definitely wrong without knowing the kind of machine and of boot
media.

	Gabriel.


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Not in the compilation, but since when do you use
cvs/rsync/bitkeeper/whatever ?

cvs since Tridge showed it to me a few years ago and how to use it well,
thus I used to get kernel source from samba.anu.edu.au's cvs tree often
(depending on what was using said source for), as for rsync, since I
started using ppc as Paul keeps his kernels on linuxcare.com.au
available over rsync. Anyway I was just using them as current examples
where gzip and bzip2 are not required, just as you used the fact
generally kernel's are obtained in tar.{gz,bz2} format as an argument
for needing the appropriate tool. I still would say the Changes file is
not out of date or anythng (as you previously suggested) as there is no
requirement for gzip or bzip2 to build the kernel from source, this is
what the file claims to cover. However this is just being picky.

The official source tree (the mirrors of ftp.kernel.org) is still only
available as gz and more recently with bz2. So historically gzip has been
a prerequisite to look at the kernel source and build your kernel, that's
all what I claimed (did you use Linux and build your kernels from
ftp.funet.fi in 1995 ?).

well until recently I only had x86 boxes, but admittedly the argument is
academic as you wont find a linux box on which you compile kernels (ie
not some small embedded system, etc etc) without gzip installed.


--
sjh@wibble.net http://wibble.net/~sjh/
Look Up In The Sky
   Is it a bird?  No
      Is it a plane?  No
         Is it a small blue banana?
YES

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