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From: Tobias Geerinckx-Rice <me@tobias.gr>
To: Vagrant Cascadian <vagrant@debian.org>
Cc: Leo Famulari <leo@famulari.name>,
	Alexandre Oliva <lxoliva@fsfla.org>,
	guix-devel@gnu.org
Subject: Re: ISO image: to xz or not to xz?
Date: Mon, 03 May 2021 21:12:25 +0200	[thread overview]
Message-ID: <87a6pbocme.fsf@nckx> (raw)
In-Reply-To: <87bl9ru3ms.fsf@yucca>

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Hi Vagrant!

Tangent: I sense some undeserved mysticism surrounding squashfs. 
It is not designed to be loop-mounted, any more than ext2 was.  It 
does not enjoy it.  People should stop doing it.

But they won't, because many distributions still insist that the 
same installer image must be both a bootable CD/DVD *and* boot 
when dd'd to a USB drive, on every PC ever made.

That ‘isohybrid’ dream justifies doing unmentionable things to an 
iso9660 file system (and only an iso9660 file system), so they 
must put the real squashfs on top of that and loop-mount it and 
ignore the screams I guess and--

...sorry; I got carried away.

Vagrant Cascadian 写道:
> Well, the suggestion to use squashfs does bear merit;

It's not a *bad* suggestion, just a bit obvious.

> it would require
> having some type of writeable filesystem on top, such as using 
> overlay
> fs to mount the installer rootfs with squashfs for the readonly 
> bits,
> and tmpfs for the writeable bits.

We've always done this.

> As a bonus, using a tmpfs overlay would solve the issue brought 
> up
> recently by someone who tried using the same installer image 
> multiple
> times, and /gnu/store and /var/guix got out of sync due to the 
> cow-store
> only writing to the newly installed system, so that the second 
> install
> failed.

...so no, it definitely wouldn't, but I think it's valuable to 
understand why you thought so!

Could you elaborate?

> Another angle might be to use a compressable but writeable 
> filesystem
> (btrfs?).

A persistently mutable . . . installation medium . . . ?

Very lost, slightly frightened,

T G-R

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  reply	other threads:[~2021-05-03 19:12 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-28 20:18 ISO image: to xz or not to xz? Ludovic Courtès
2021-04-28 20:39 ` Vincent Legoll
2021-04-28 20:41 ` Simon Josefsson via Development of GNU Guix and the GNU System distribution.
2021-05-02 21:16   ` [PATCH] maint: Do not xz-compress ISO images Ludovic Courtès
2021-05-03  0:15     ` [bug#48173] " Julien Lepiller
2021-05-03  7:50       ` François
2021-05-03 15:39       ` bug#48173: " Ludovic Courtès
2021-05-03 16:35         ` Julien Lepiller
2021-05-04  3:35           ` Maxim Cournoyer
2021-05-03 15:54       ` Ludovic Courtès
2021-04-28 21:16 ` ISO image: to xz or not to xz? Christopher Baines
2021-04-28 21:18 ` Leo Famulari
2021-05-03 16:47 ` Alexandre Oliva
2021-05-03 17:07   ` Leo Famulari
2021-05-03 17:30     ` Vagrant Cascadian
2021-05-03 19:12       ` Tobias Geerinckx-Rice [this message]
2021-05-03 19:57         ` Vagrant Cascadian
2021-05-03 17:41   ` Tobias Geerinckx-Rice

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