ez-bios w:loadlin w:_umsdos.gz

ez-bios w:loadlin w:_umsdos.gz

Post by James Stewar » Fri, 11 Jan 2002 09:01:59

 what distros do the loopback? Can you elaborate on how this works.

"Loopback" is the linux method of installing a filesystem inside another
one.  For example, you can download one of those .iso CDROM images and then
mount the downloaded file as if it was a real CDROM in a drive except that
it is really a file on a filesystem.

This mechanism is like the 'drivespace', 'doublespace' 'stacker' or
'superstore' disk compression software that can compress a FAT file system.
It simply loads it all into a single compressed file and 'mounts' it as
drive c:

There are Linux distributions out there that use this to embed it's native
EXT2 (or whatever) filesystem in a single file, then put it on a non native
filesystem (like FAT32).  One that I like is called Peanut Linux
(http://www.ibiblio.org/peanut) .  It is about a 100 meg download, is fairly
mature, up to date, has an X11 based GUI, and is based on Slackware.
Therefore you can install any missing pieces from your slackware distro.
Try it out.  There many others, consult http://lwn.net/Distributions/ and go
through the list.


Also I remember reading a doc about Lilo that had a statement like: "lilo
automatically recognizes soft-BIOS such as Ontracks Disk Manager ...".  I
can't remember if EZ-BIOS (EZ-DRIVE?) was on that list or not, plus I can't
seem to find the document.  My gut feeling is that it probably will.


Anyway, back to the original problem of installing Linux on an already
partitioned and FAT formated drive with EZ-BIOS on it:

Go ahead and attempt to install a DOS/FAT based Linux, such as
ZIPSLACK/BIGSLACK (DMS-DOS based) or a loopback Linux like Peanut or (Phat
Linux?).  Here is how the installation will go:

The first thing that will happen is that you will be booted into a linux
kernel, either from a boot floppy (put it in after the EZ-BIOS loads just as
EZ-BIOS says to) or from a batch file running 'loadlin" from a DOS mode

In either case, these installers usually work this way:  They load a
RAMDISK, then boot the kernel, and mount the RAMDISK as the root filesystem.
They do this all using BIOS calls.  They never touch your hard drive until
you (or the install program) tells them too.  Very safe.

Then the setup program will procede to ask you where the 'install source
files' are and where the target where you want the files installed at is.
During these steps, you are fully in Linux using protected mode (no BIOS
access).  Upon mounting file systems, Linux does simple sanity checks, if
there is anything wrong, you'll surly get a message about it and will be
able to abort before anything could be destroyed.  In fact, Linux will
probably refuse to mount anything that it doesn't fully understand. (Just
don't mount an NTFS file system writeable, but that's another story).

Now come the critical parts:

Make sure you correctly instruct the installer to install Linux to an
existing DOS filesystem (either using loopback or DMS-DOS).  Be careful not
to tell it to erase an existing partition and install it's own EXT2
partition there.  If you have any questions, abort the installer and read
the install docs for the distribution

If it asks to install a 'bootloader' such as lilo or grub, say NO.   You
will be running Linux by first booting into DOS mode (non windows GUI if you
are in Win9x) then running a batch file with 'loadlin.exe' in it.  DOS mode
uses EZ-BIOS, boots into Linux which bypasses the whole BIOS thing and reads
the drive correctly (if the installer was able to do it above) using it's
own drivers. You may want to build a boot floppy if the installer gives you
an option for it.

One final thing that can get you:  Some distributions default the IDE hard
drive driver to DMA mode.  If you have a flakey motherboard setup (such as
an old VIA chipset running at 83 Mhz FSB speed), you can corrrupt your
filesystem.  Slackware distro's don't enable DMA by default ... yet.  You
may want to once you feel it's safe.

I am confident that you won't wipe out your hard drive unless you do
something stupid during the install process like format a partition, or let
it do an 'normal' ext2 installation instead of a "install to a DOS
partition" install.  Usually the installer instructions are clear about
this.  Read the install docs for the distribution that you are going to
install carefully.