Bug#864777: initramfs-tools: Please support a tmpfs boot mode

From	Benjamin Drung <benjamin.drung@profitbricks.com>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#864777: initramfs-tools: Please support a tmpfs boot mode
Date	2017-12-14 13:30 +0100
Message-ID	<uWAOd-751-1@gated-at.bofh.it> (permalink)
References	<tSiS5-75d-1@gated-at.bofh.it> <tXNLz-3oJ-7@gated-at.bofh.it> <tSiS5-75d-1@gated-at.bofh.it> <tXNLz-3oJ-7@gated-at.bofh.it>
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Hi Peter,

Am Donnerstag, den 29.06.2017, 15:55 -0400 schrieb Peter Colberg:
> Hi Benjamin,
> 
> On Wed, Jun 14, 2017 at 05:47:54PM +0200, Benjamin Drung wrote:
> > Package: initramfs-tools
> > Version: 0.130
> > Severity: normal
> > Tags: patch
> > 
> > Hi,
> > 
> > The tmpfs boot mode allows one to operate a disk-less live system
> > by
> > downloading a root tarball (that can be created with debootstrap)
> > and
> > extracting it to a tmpfs root partition.
> > 
> > The tmpfs boot mode is similar to the nfs boot mode, but it does
> > not
> > rely on any external service (after booting). We use this boot mode
> > for
> > our compute nodes. I have attached a patch to support this boot
> > mode and
> > tested it with qemu and on real hardware.
> 
> Please take a look at the package live-boot (and the man page of the
> same name in live-boot-doc). Specifically, the parameter fetch=URL
> should satisfy your requirements and consume less resources.
> 
> live-boot creates an overlay filesystem backed by a squashfs image,
> which means it likely uses much less RAM than copying root to tmpfs.
> (For my system, squashfs reduces the required memory to a third.)

I took a look at the live-boot package and we will evaluate the RAM
savings and performance penalty. Expect a patch for live-boot to
support live-{top,premount,bottom} hooks.

Some statistics: Our xz compressed root tarball is around 180 MB in
size and consumes 690 MB extracted. Our initrd uses 9 MB. The initrd
from live-boot uses 17 MB. Let's see if the live-boot initrd can be
stripped down as well.

For now, I updated my patch to add an option to enable/disable support
for the tmpfs boot mode. Updated patch is attached.

-- 
Benjamin Drung
System Developer
Debian & Ubuntu Developer

ProfitBricks GmbH
Greifswalder Str. 207
D - 10405 Berlin

Email: benjamin.drung@profitbricks.com
URL: https://www.profitbricks.de

Sitz der Gesellschaft: Berlin
Registergericht: Amtsgericht Charlottenburg, HRB 125506 B
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Bug#864777: initramfs-tools: Please support a tmpfs boot mode Benjamin Drung <benjamin.drung@profitbricks.com> - 2017-06-14 18:00 +0200
  Bug#864777: initramfs-tools: Please support a tmpfs boot mode Peter Colberg <peter@colberg.org> - 2017-06-29 22:00 +0200
    Bug#864777: initramfs-tools: Please support a tmpfs boot mode Benjamin Drung <benjamin.drung@profitbricks.com> - 2017-12-14 13:30 +0100

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