From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Rob Landley <rob@landley.net>,
Taras Kondratiuk <takondra@cisco.com>,
Arvind Sankar <nivedita@alum.mit.edu>
Cc: initramfs <initramfs@vger.kernel.org>,
Victor Kamensky <kamensky@cisco.com>,
linux-security-module <linux-security-module@vger.kernel.org>,
Al Viro <viro@ZenIV.linux.org.uk>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
Date: Mon, 16 Apr 2018 11:46:05 -0400 [thread overview]
Message-ID: <1523893565.3272.191.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <8d6b1fcc-1a21-1707-dd8e-43529e1d644c@landley.net>
Hi Rob,
On Thu, 2018-02-01 at 17:34 -0600, Rob Landley wrote:
>
> On 02/01/2018 04:41 PM, Taras Kondratiuk wrote:
> > Quoting Mimi Zohar (2018-02-01 13:51:52)
> >> On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote:
> >>> On 02/01/2018 09:55 AM, Mimi Zohar wrote:
> >>>> On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote:
> >>>>
> >>>>>> With your patch and specifying "root=tmpfs", dracut is complaining:
> >>>>>>
> >>>>>> dracut: FATAL: Don't know how to handle 'root=tmpfs'
> >>>>>> dracut: refusing to continue
> >>>>>
> >>>>> [googles]... I do not understand why this package exists.
> >>>>>
> >>>>> If you're switching to another root filesystem, using a tool that
> >>>>> wikipedia[citation needed] says has no purpose but to switch to another
> >>>>> root filesystem, (so let's reproduce the kernel infrastructure in
> >>>>> userspace while leaving it the kernel too)... why do you need initramfs
> >>>>> to be tmpfs? You're using it for half a second, then discarding it,
> >>>>> what's the point of it being tmpfs?
> >>>>
> >>>> Unlike the kernel image which is signed by the distros, the initramfs
> >>>> doesn't come signed, because it is built on the target system. Even
> >>>> if the initramfs did come signed, it is beneficial to measure and
> >>>> appraise the individual files in the initramfs.
> >>>
> >>> You can still shoot yourself in the foot with tmpfs. People mount a /run
> >>> and a /tmp and then as a normal user you can go
> >>> https://twitter.com/landley/status/959103235305951233 and maybe the
> >>> default should be a little more clever there...
> >>>
> >>> I'll throw it on the todo heap. :)
> >>>
> >>>>> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs
> >>>>> is configured in, even when you're then going to overmount it with
> >>>>> something else like you're doing, let's just _remove_ the test. If it
> >>>>> can be tmpfs, have it be tmpfs.
> >>>>
> >>>> Very much appreciated!
> >>>
> >>> Not yet tested, but something like the attached? (Sorry for the
> >>> half-finished doc changes in there, I'm at work and have a 5 minute
> >>> break. I can test properly this evening if you don't get to it...)
> >>
> >> Yes, rootfs is being mounted as tmpfs.
> >
> > I don't think you can unconditionally replace ramfs with initramfs by
> > default. Their behavior is different in some cases (e.g. pivot_root vs
> > switch_root)
>
> Both are switch_root, you can't pivot_root off of either one. (Yes, I
> hit that bug and reported it, and they fixed it, back in the day...
> http://lists.busybox.net/pipermail/busybox/2006-March/053529.html )
>
> > and it can break many systems that expect ramfs by default.
>
> The use case I told Mimi about off-list (since they stopped cc:ing the
> list in one of their replies but the conversation continued) was the guy
> who was extracting an initramfs bigger than 50% of system memory, which
> worked with initramfs but failed with initmpfs. A quick google didn't
> find the original message but it resulted in this blog entry from the
> affected party:
>
> http://www.lightofdawn.org/blog/?viewDetailed=00128
>
> I.E. yeah, I know, I need to redo these patches tonight.
I'd really like to be able to have rootfs be a tmpfs filesystem. Any
time estimate on this patch?
thanks!
Mimi
next prev parent reply other threads:[~2018-04-16 15:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-30 21:46 [RFC PATCH] rootfs: force mounting rootfs as tmpfs Mimi Zohar
2018-01-31 19:32 ` Rob Landley
[not found] ` <1814af5c-170d-39c0-58fd-02eb7216e008-VoJi6FS/r0vR7s880joybQ@public.gmane.org>
2018-01-31 22:07 ` Mimi Zohar
2018-01-31 23:48 ` Rob Landley
[not found] ` <a538e55c-81ca-6d59-20cf-21b47387c3e2-VoJi6FS/r0vR7s880joybQ@public.gmane.org>
2018-02-01 2:03 ` Arvind Sankar
2018-02-01 4:22 ` Mimi Zohar
[not found] ` <1517458921.3329.2.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2018-02-01 15:20 ` Rob Landley
2018-02-01 15:55 ` Mimi Zohar
[not found] ` <1517500500.3974.45.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2018-02-01 17:09 ` Rob Landley
[not found] ` <875e5d2d-9ffe-14ab-090a-4a9632af0f35-VoJi6FS/r0vR7s880joybQ@public.gmane.org>
2018-02-01 21:51 ` Mimi Zohar
[not found] ` <1517521912.3619.0.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2018-02-01 22:41 ` Taras Kondratiuk
2018-02-01 23:34 ` Rob Landley
2018-04-16 15:46 ` Mimi Zohar [this message]
2018-02-01 22:46 ` Rob Landley
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