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From: Vagrant Cascadian <vagrant@debian.org>
To: Tobias Geerinckx-Rice <me@tobias.gr>
Cc: guix-devel@gnu.org
Subject: Re: ISO image: to xz or not to xz?
Date: Mon, 03 May 2021 12:57:05 -0700	[thread overview]
Message-ID: <878s4vtwtq.fsf@yucca> (raw)
In-Reply-To: <87a6pbocme.fsf@nckx>

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On 2021-05-03, Tobias Geerinckx-Rice wrote:
> 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.

The only mysticism I see here is attributing enjoyment to a
filesystem. :)

Is mounting on a loopback device really any different from any other
block device?


> 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--

Never heard the screams; what frequency does squashfs emit screams at?
:)

People have made it work well enough for only slightly less long than I
can remember using free software operating systems...


> Vagrant Cascadian 写道:
>> Well, the suggestion to use squashfs does bear merit;
>
> It's not a *bad* suggestion, just a bit obvious.

Fair enough.


>> 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.

I *thought* so, but...


>> 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?

Mostly I was referring to:

  https://lists.gnu.org/archive/html/guix-devel/2021-04/msg00546.html

Though I haven't confirmed that behavior myself. Probably deserves a
proper bug report.


live well,
  vagrant

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  reply	other threads:[~2021-05-03 19:57 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
2021-05-03 19:57         ` Vagrant Cascadian [this message]
2021-05-03 17:41   ` Tobias Geerinckx-Rice

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