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Re: A fuse based initfs



Jon Nettleton wrote:
On 8/23/07, Jon Nettleton <jon nettleton gmail com> wrote:
On 8/23/07, Andrew Bartlett <abartlet samba org> wrote:
On Thu, 2007-08-23 at 18:02 -0400, Jon Nettleton wrote:
On 8/22/07, Douglas McClendon <dmc fedora filteredperception org> wrote:
In general, it sounds like you are outlining several different
problem/solutions, but I don't think they all need to be as tightly
integrated as you suggest.

For instance, the gdm in initramfs (or very very early).  Why do you
need this copy-on-write rootfs stuff?  Why not just have a tmpfs, and a
gdm configuration that looks there.  Likewise for the early logging
stuff.  Later during boot, the early-boot logfiles in tmpfs can be
copied to /var/log.  This isn't as nice as the magic
unionfs/dm-snapshot-merge automagic merging.  But I don't think that is
necessary and worth the steps you are taking to get it.
The problem is that all the X gdm talk is through fifo sockets.  This
busies the filesystems
and makes it impossible to just copy things around.  If we want the
boot process to be
smooth and seamless we are going to need some sort of ability to write
to a "read only" filesystem in place.
Why not just put the fifo on a tmpfs, and keep it around for the life of
the system.  Being tmpfs, it cleans up nicely when shut down.  There are
many other reasons to move the X socket from /tmp (selinux etc).

Would a permanent symlink from /tmp -> a tmpfs mounted on /var/run/X
solve the legacy issues?

That only leaves some log issues.  However if other people have no
problems with /var/run/X and /var/run/gdm being tmpfs or ramfs then
this is do-able.


actually thinking about this.  Moving these files to a tmpfs/ramfs
filesystem will actually allow us to remove a bunch of cleanup code in
rc.sysinit for stale filehandles and directories.

hmmm...this is sounding better by the minute.

Over on fedora-livecd-list, I'm working on using something like a usbstick instead of ram for the read-write overlay on top of the read-only ext3fs image (that is on the livecd, living in a squashfs).

One of the issues was getting things unmounted cleanly at shutdown. While one gross method I used, turned out to not be necessary or the right approach, while talking about it, the rather logical idea came up of keeping the original initramfs around, and using it to tear things down, just as it is used to build things up.

E.g. to eject the livecd at shutdown. You need the eject command, and a completely unmounted rootfs. Using a tmpfs, or perhaps more logically, using the tmpfs from the original initramfs, seems like the way to do this.

And that seems like it might mesh well with the idea of gdm in initramfs that I think you are talking about.

(and maybe somebody can correct me, but does the original initramfs really, truly get unmounted currently? Or is it just lazy unmounted, and it is really hanging around hidden somewhere?)

-dmc



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