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ZyX LiveInstaller:: Frequently Asked Questions
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Q:
Why did you do this?
A:
I am very happy to say that I haven't 'really' used microsoft windows
in a very long time. And I'm willing to grant that they do have smart
people working for them, and there did seem to be vast improvements
between 98 and XP. But, niceties asside, the reason I chose a life path
and niche career where I wouldn't have to 'really' use MS 'winblowz', is
because of the nightmare user experience their OS provided for many years.
I'm talking about reboot and reboot and reboot. Install a driver, reboot
(perhaps several times). Crash (on a daily basis), reboot. Install
software, reboot. It just really bothered me as a computer engineer, to
the point where whenever I would use any system, and have to reboot, I
would hear a voice in my head question why the reboot was happening, and
if better design and programming could have prevented the need to do it.
So as soon as brain grok'd devicemapper enough to realize that this could
be done, well... it had to be done :)
Note, I must give credit to Bill Rugolsky Jr. in a discussion on
fedora-livecd-list[1a] back in March'06, he first introduced me to the
idea of using devicemapper to migrate data from a LiveCD to disk. His idea
however was to migrate the readonly squashfs filesystem to disk, so that it
would be effectively 'cached'. I then figured out the next logical step of
migrating the ext3 part of the readonly squashfs *and* the readwrite
overlay, to result in something effectively identical to a tradionally
installed and running system (sans cold, or even kexec-warm reboot).
[1a]
https://www.redhat.com/archives/fedora-livecd-list/2006-March/msg00276.html
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Q:
Does this require respinning or massive modification to the LiveOS?
A:
For the standard Fedora LiveOS releases, probably as far back as they
go- No. There was a version of this I posted to fedora-devel 2 years ago
that required either respinning or some painful manual early boot commands.
But very shortly after I released that, I figured out how to avoid that,
and mentioned that on fedora-devel as well. I'm not sure if they believed
me at the time, but not a single person expressed any interest in finding
out.
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Q:
Will including this in my LiveOS spin be dangerous and have bad side-
effects?
A:
The size of the .i386.rpm is <150kb. The code should only run if and
only if the user launches the installer from the SystemTools desktop menu.
The priveledged execution configuration(pam/consolehelper) is a 100% copy
of that of the traditional fedora anaconda/liveinst installer. But by all
means, this is at the moment very alpha software, in need of good peer-
review and critique.
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Q:
Doesn't SuSE already have a rebootless installer?
A:
In some sense yes. But not in the sense that the user can be surfing
the web with firefox, running from a LiveCD/DVD/USB, then if they decide,
launch a process which will install the OS they are using to surf the web
with to disk, and when done, be able to eject the install CD/USB, never
having had to stop using their web browser (or any other application).
Rather, what I believe SuSE achieves, is saving several seconds that was
historically spent doing a 'cold' or 'warm' reboot involving BIOS
reinitialization of hardware. Otherwise, their users still witness every
process running on the computer, come to a synchronous end, while the user
watches every OS initialization program and script, run again. To me, I
call that a 'reboot experience'. If they really want to call that
'rebootless installation', well, more power to them.
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Q:
Were you the first person to write a rebootless OS installer?
A:
Perhaps, if you restrict the question to the sense of a fully usable
LiveOS installer. I suspect some things done 10+ years ago might fall
under the terms, but those did not present you with a completely usable
workstation prior to installation that remained unaffected through and
after installation. Also, I am definitely the second person to have
described the process online, though perhaps the first to have implemented
it. Only after I was well into my implementation did I discover that
Goswin Brederlow had outlined more or less the same implementation years
earlier-
http://www.mail-archive.com/debian-boot@lists.debian.org/msg28182.html
However I have never been able to find anything publically available
that resulted from that discussion.
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Q:
What happens to my seperate LiveUSB /home data partition/file?
A:
For the moment, nothing. If your LiveUSB /home is mounted from
a seperate file or partition on the LiveUSB (i.e. during LiveUSB creation
you allocated space for a seperate /home area), then it will remain
seperately mounted after installation. In part, I am really awaiting
feedback from serious users of such configurations to let me know how they
think it should be handled. This is because I have more than one thought
on how to better address the situation, but don't necessarily want to
implement all the alternatives along with a selection mechanism. Let me
know what you think should happen by default in this situation.
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Q:
What is this issue with unionfs with future Fedora releases?
A:
At the inception of official Fedora LiveCDs (i.e. Fedora-6 if I recall
correctly), Fedora(/DavidZ), partially inspired by a report I wrote[2] on
the Linux From Scratch LiveCD architecture, decided to utilize devicemapper
snapshots to facilitate a LiveCD that supported a fully read-write root
filesystem. The more popular alternative at the time, and since, found in
Knoppix and Ubuntu, was to use unionfs instead of devicemapper snapshots to
provide the RW-rootfs capability. I was such a non-ubuntu user at the time,
that when I wrote that report, I actually did not know that ubuntu had already
used devicemapper snapshots briefly, before switching out to unionfs, and that
in all likelyhood, that is where LFS picked up on the technique. The primary
benefit of unionfs as a LiveOS architecture over devicemapper snapshots, might
be the slightly more intuitive way that one can work with the overlay, as an
easily accessible set of files, as opposed to a low level collection of
modified disk blocks. This also leads to easier recovery from storage
exhaustion scenarios, as deleted files can trivially reclaim space in the
overlay. Wheras to as easily recover space in the dmsnapshot case, requires
code currently theorized, but not yet written. Because of this,
LiveCD/USB/OSs, both unionfs and dmsnapshot based, but particularly dmsnapshot
based, are not terribly well suited to long term use. One thing to remember
with the zyx-liveinstaller, is that once the installation completes, none of
these complications matter any more, as the system is now effectively
identical to a traditionally installed system... without rebooting even one
time. Now then, digressing a bit from background, going back to the original
question- The reason that the zyx-liveinstaller will cease to work on stock
Fedora, if they move to a unionfs based architecture, is because the
devicemapper snapshot nature of the LiveOS, is key in facilitating rebootless
installation. With unionfs, you can try to do something similar, but if a
filehandle is open (as many always are) on the installation media, there is
no current way (that I know of) to seperate that media from the OS, without
suffering stale broken filehandles, on system critical files.
So should Fedora switch to unionfs for the LiveOS rootfs, which it may do as
early as F13, the zyx-liveinstaller, would THEN AND ONLY THEN, require a
custom respin to work with Fedora. Also, note that unionfs being available
in Fedora, is not the same thing as switching to it for the LiveOS
architecture. Should unionfs be in the mainline kernel, and in Fedora, but
not used for the LiveOS architecture, then the zyx-liveinstaller would
continue working on completely stock Fedora LiveCD/DVD/USBs.
[2] In mid 2006, using the alias Jane Dogalt, I published my first
implementation outline[2a] of Rebootless LiveOS Installation, in response to
discussion of SuSe style kexec bios-skipping-but-still-a-warm-reboot based
installation. Shortly thereafter, Fedora(/DavidZ), implemented the first
official Fedora LiveCD, built with the pilgrim/mayflower toolset/scripts
which provided the foundation for the current livecd-creator/tools. In that
first release's README.fedora[2b] file, davidz even referenced that post
(search for 'rebootless' in the linked page), and specifically, the
facilitation of rebootless liveos installation. Though he characterized it
as 'bluesky', whatever that means.
2a:
http://www.redhat.com/archives/anaconda-devel-list/2006-August/msg00028.html
2b:
http://cgit.freedesktop.org/~david/pilgrim/commit/?h=bd9ff3dbce8ef5996be5ec23f999c7914fa7a656&id=31fb7988f302ea9ae98f6f77d4a158a774801eff
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