Re: [9fans] mounting a 9660 file system - writeable

[Dave Eckhardt <davide+p9@cs.cmu.edu>]

9660srv's job is to serve the files stored on a CD-ROM.  CD-ROMs
are more or less read-only, so 9660srv serves the files as read-only
as well.

In most setups, the /tmp file system is "stored" in RAM.  It's faster
than sending the data to some storage device, and when you turn the
machine off the files vanish, which matches the mental model people
sometimes use when putting things in /tmp.

If you want to write files that persist across reboots, you'll need
to use some other kind of file system (and give it a storage
partition).  Assuming you're using 9front, you might start looking
somewhere around here:

  https://fqa.9front.org/fqa7.html#7.1.2

You might give your VM two storage devices, one blank and one holding
the ISO image; running the installer on the ISO image would guide
you through installing a regular read/write file system on the other
storage device.

If you wanted to layer your changes on top of an underlying CD-ROM
image, that could be done with an overlay file system.  One of my
students wrote one many years ago:

  http://9p.io/wiki/plan9/divergefs/

Later other students used it to build kernels without write access
to /sys/src -- their overlay contained their source changes and
also their object files.  The overlay file system will still need
somewhere to store files, though.

Dave Eckhardt

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