sysinstall and mfs

Jerry McAllister jerrymc at
Thu Feb 4 22:27:35 UTC 2010

On Thu, Feb 04, 2010 at 03:31:33PM -0600, Martin McCormick wrote:

> 	It appears that the same sysinstall executable that
> works fine when run from the installation CDROM malfunctions
> when run from a mfs platform even though it finds the disk it is
> supposed to install on.
> 	One can format the disk manually and mount the
> partitions under mfs, but sysinstall can't seem to do the
> installation. This does not make sense, but that is the score
> right now.

I don't understand why you are trying to do your own MFS for this.
You need to be booted to the MFS for it to make any difference and
that is what the install image (from the CD) normally does.  If you
just create an MFS and copy sysinstall to it, it will make no 
difference in its ability to modify the labels on the system disks.
They are already busy and you would have to reboot to unbusy them
and then you lose the MFS.   You could muck around and go down to
Single User and maybe come up running from MFS and free up the disk, 
but don't know a way to do that.

What happens when the boot or fixit is running is that you are booted
to a special filesystem that resides in MFS.  The system copies over
what it needs from the CD (or floppies) and runs from there.   Mainly
it is a filesystem and it allows nothing else but the MFS and the
boot media (CD/Floppy) to be mounted.   Then the hard disk is free to
diddle with the labels on.   If you do an install of something on to
the hard disk, then it creates a mount point within that Memory Filesystem 
and mounts the disk partition to it.   I don't know the naming
convention that it uses for the mount points, but it could be anything
such as iroot, iusr, etc or maybe something based on the partition name
such as mda1s1a, mda1s1d, etc.    Maybe they make an mroot and then
put the rest of the mount points in that mroot directory just like they
will be in a running system.   So, if there are more than root partitions
they would look something like  /mroot, /mroot/tmp, /mroot/usr, etc.
Guess I should poke around sometime and see what they call them - sometime
when I have a lot of extra time.

The system uses these to install the software and then when it reboots, 
these temporary mount points disappear and when the new system comes
up, it just uses the mount points written in the /etc/fstab file (or in
the  /mroot/etc/fstab  file before the reboot when still doing the install)

This is rambling too much.   The point is that MFS is only meaningful
in this situation if the system is booted and running from it.  It 
does not mean anything to sysinstall otherwise.

There are other uses for MFS such as a handy device for creating
these boot images, but that has little bearing on how sysinstall runs.


> Martin McCormick
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