Re: Unionfs (was: Re: [gentoo-catalyst] Keeping a test environment using catalyst)

[Paul Smith]

%% Chris Gianelloni <wolf31o2@g.o> writes:

  cg> I'm just curious why this needs to be done within the initrd, at
  cg> all.  I guess it could be, but I could also see it working outside
  cg> the initrd.

If you do it after initrd, you'll have to be very, very careful.
"Outside" the initrd you've invoked the real init, and it's starting to
bring up the system.  If you haven't already set up the unionfs before
that, you better be darn sure you do it immediately... if not you will
have applications coming up with the wrong configs, failing because they
can't write to /etc and/or /var, etc.

  cg> Anyway, if we were to do it, we would allow for mounting a USB key
  cg> or other such device.  Most likely, it would be via a
  cg> unionfs=/dev/$blah option, that would mount that device, along
  cg> with the CD, as a unionfs.

Yes.  I have this working right now, although it just uses a ramdisk
today.  Obviously using my current method, in order to use a keydisk or
maybe even a file on a FAT partition which contains an ext2 partition
and is mounted as a loop FS, you would need to add smarts to the initrd
(linuxrc) to detect the hardware and mount those partitions.

  cg> One thing I probably would *not* do is make the entire CD a
  cg> unionfs, as I just think it would be a waste of energy and would
  cg> make troubleshooting much harder.

I'm not sure what you mean by "not make the entire CD a unionfs"...?  Do
you just mean that some root directories would not link to the unionfs
but instead would go to the cdrom?  Or...?

  cg> Things like /var, /etc, /root, and /home would definitely be cool
  cg> to not only be writable, but also survivable from a reboot.

Yes, that's the ultimate goal of course.

-- 
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 Paul D. Smith <psmith@××××××.com>           HASMAT--HA Software Mthds & Tools
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist
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   These are my opinions---Nortel Networks takes no responsibility for them.
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