[Fedora-livecd-list] Re: help understanding the livecd-creator tool - i need to make some customizations
Thanks for the reply John.
On 06/14/2016 11:38 AM, John Florian wrote:
Not sure I follow exactly what you're trying to achieve. Images
produced by livecd-tools already provide an overlay backed by tmpfs so that /etc, /var and
more functionally are writable. However, those changes are not persistent -- if you
reboot you're back to the original image.
Can you tell me more where this tmpfs
overlay happens? What step in the
livecd-creator process does this get configured and where does it happen
during the boot of the LiveOS?
I'm ok with the non-persistent changes; in fact, that's exactly what I'm
looking for. What I'm looking for is that the rest of the filesystem
(where possible without breaking function) is read-only. I assume this
shouldn't be difficult since squashfs was designed for read-only. Is the
overlay to allow writing done via unionfs or something like it?
If you truly want the root fs to be read-only, you might be able to use "mount -o
remount,ro" somehow but lots more will likely be broken. You may want to look into
the dracut modules that do all the mounting work. In particular,
/usr/lib/dracut/modules.d/90dmsquash-live/dmsquash-live-root.sh may be informative. Also
worthy of note, dracut is really flexible at letting you wedge things in. I've done
this, but developing/testing is a chore considering you need to respin your image to test
your new boot hooks.
Where in the livecd-creator process does it call dracut? I
assume this
is what is used to create the initramfs?
--
John Florian
> -----Original Message-----
> From: B. Masuda [mailto:bond.masuda@jlbond.com]
> Sent: Tuesday, June 14, 2016 14:10
> To: livecd(a)lists.fedoraproject.org
> Subject: [Fedora-livecd-list] help understanding the livecd-creator tool -
> i need to make some customizations
>
> hello,
>
> i need to create a liveOS DVD with some unique requirements:
>
> 1) the root file system will be mounted directly off the DVD in read-only
> mode
> 2) i want to use in-memory disk for only /etc and /var for temporary non-
> persistent read-write
>
> i have practiced using the livecd-creator tool to build a fedora-live-
> workstation and centos-7-livecd as a way to get familiar with the tool. it
> seems to me that the type of changes I want to make above, are not done in
> the kickstart %post section, so I assume it is done as part of the livecd-
> creator tool. I've read the README files, but I don't see a detailed
> description of how the root file system is configured to mount for the
> LiveOS. Looking over the steps described in the README, I *think* I need
> to better understand the following steps:
>
>> Creates a live CD specific initramfs that matches the installed kernel
>> Configures the boot loader
> Is this the right direction to figure how to accomplish my above stated
> goals? If not, please help redirect me. If so, please help me understand
> those steps in more detail and how I can modify them to suite my needs.
>
> thanks in advance...
> --
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