Re: [DNG] installer messes up swap partition on multi-boot

[Boruch Baum]

On 03/23/2016 01:01 AM, Go Linux wrote:
> On Tue, 3/22/16, Daniel Reurich  wrote:
> 
>> 
>> Given that suspend2disk uses the swap volume I'd recommend never 
>> using the same swap space for different linux systems anyway in a 
>> multi-boot setup.
>> 
> 
> 
> 
> Now I'm confused.  I thought that suspend used RAM and hibernate used
> swap. Oh wait . . .  suspend2disk isn't even in the devuan repos. Now
> I'm really confused.  Aside from that, I have shared swap partitions
> in the past.  I had no idea that was a nono.


> Learn something new everyday (if you're lucky).
Don't 'learn' anything just yet from what Daniel initially wrote. I (or
someone quicker than me) need to see and report back the condition under
which a boot performs a resume from suspend. Otherwise, what would be
the use-case of OS#2 resuming using a swap partition loaded with data
from OS#1's suspend?

> 
> golinux
> 
> 
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Re: [DNG] installer messes up swap partition on multi-boot

[Daniel Reurich]

On 23 March 2016 6:01:23 PM NZDT, Go Linux  wrote:
>On Tue, 3/22/16, Daniel Reurich  wrote:
>
>> 
>> Given that suspend2disk uses
>> the swap volume I'd recommend never using the same swap space for
>> different linux systems anyway in a multi-boot setup.
>> 
>
>
>
>Now I'm confused.  I thought that suspend used RAM and hibernate used
>swap. Oh wait . . .  suspend2disk isn't even in the devuan repos.  Now
>I'm really confused.  Aside from that, I have shared swap partitions in
>the past.  I had no idea that was a nono.  Learn something new everyday
>(if you're lucky).
>
hibernate=suspend2disk=s2disk

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Re: [DNG] installer messes up swap partition on multi-boot

[Boruch Baum]

On 03/23/2016 12:19 AM, Daniel Reurich wrote:
> Hi Boruch,
Good morning!

> 
> On 22/03/16 09:29, Boruch Baum wrote:
>> On today's install device, I had a pre-existing linux with a swap 
>> partition on the disk, and the partitioner insisted on
>> re-formatting it.
> 
> 
>> This is BAD. It changes the UUID of the swap partition, which
>> messes up the other operating systems on the device, because the
>> recent 'best practice' has been to identify partitions in fstab by
>> UUID.
> 
> Did it really? Good - so it should!! If you selected using that
> existing swap volume, I think that it's a reasonable default for it
> to format it. Same goes for any other volume except /home.  If you
> had reason to not want it formated then you should have to mark it to
> not be formatted.
That's not what happened, and I see there was room in what I wrote to be
misunderstood. I did NOT select the swap partition in any way; it was
auto-detected by the installer. Also, I did try to ask the installer to
not format the partition, but there was no such option. My memory is
that there was a column on the installer screen with the letter 'F' or
'f' that seemed to indicate that the partition was to be formatted, but
that it was immutable. When selecting the partition, my memory is that
likewise the option was not available.

Since I've read recently a few posts on the list about the option of
running an 'expert' install, I'll add that I was NOT using that install
method.
> 
> This protects you from situations where you do a new install
> re-using the existing partition/volume layout and an ensures that any
> old suspend2disk data in the swap is wiped out preventing a
> corruption resulting from the next reboot from trying to restore from
> the stale suspend image.
I don't follow your logic on this, so please elaborate. My understanding
is that contents of swap can be used to restore from suspend --- when
restoring from suspend! In what situation would a re-boot try to restore
a suspend state? Let's say that one powered off from suspend - would a
re-boot perform a restore? I can't test this right now because my devuan
evaluation was installed without any desktop and doesn't have a suspend
feature.
> 
> I'm sure that the installer only would do this if you chose to set
> that partition up as swap in the first place.
Daniel, when you start saying "I'm sure ... would" you're not
engendering confidence, you're indicating that you have no idea, but
you're willing to recklessly guess, against a user's report to the
contrary. Did you check the facts before writing?

I just now went to my devuan evaluation machine and rebooted using the
install media, trying both 'expert' and regular install.

1] The only difference I see between the two install modes is that the
'expert' mode initially presents the installer's main menu, and the
non-expert mode hides the main menu until later in the install process.

2] Neither the 'expert' or the non-expert install mode had an obvious
menu entry point for the installer's partition configuration function.

2.1] As a general matter, that's undesirable, so I'd like to report that
now, and request that the installer have that as a menu item. More
immediately, its unfortunate, because it makes it difficult to
double-check the partitioner at this point.

2.2] It seems like the only way to run the installer's partitioner is to
connect to the network! I'm not interested now in opening a shell and
running fdisk or whatever, I'm interested in quickly triple-checking my
previous reports, of what the installer's partitioning front-end is
offering when auto-detecting a swap parition. I'd like to also take this
opportunity to request that the installer not require a network
connection in order to run the partitioner.

> Given that suspend2disk uses the swap volume I'd recommend never
> using the same swap space for different linux systems anyway in a
> multi-boot setup.
That's very desktop-centric advice for what's supposed to be a
"universal operating system". It also presumes the system has
suspend2disk. It also presumes (I think incorrectly) that a reboot or a
cold boot would even try to restore from suspend.

I would really like to have experimented with suspend/power-off/reboot
before writing this post, but the only devuan system I have running was
installed without a desktop or a suspend feature, and I'm in the middle
of another experiment that will last a few days, and my other desktop
on-hand isn't devuan and has too much in-progress to risk a failed
resume from suspend.


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Re: [DNG] installer messes up swap partition on multi-boot

[Go Linux]

On Tue, 3/22/16, Daniel Reurich  wrote:

> 
> Given that suspend2disk uses
> the swap volume I'd recommend never using the same swap space for
> different linux systems anyway in a multi-boot setup.
> 



Now I'm confused.  I thought that suspend used RAM and hibernate used swap. Oh 
wait . . .  suspend2disk isn't even in the devuan repos.  Now I'm really 
confused.  Aside from that, I have shared swap partitions in the past.  I had 
no idea that was a nono.  Learn something new everyday (if you're lucky).

golinux


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Re: [DNG] installer messes up swap partition on multi-boot

[Daniel Reurich]

Hi Boruch,

On 22/03/16 09:29, Boruch Baum wrote:
> On today's install device, I had a pre-existing linux with a swap
> partition on the disk, and the partitioner insisted on re-formatting it.


> This is BAD. It changes the UUID of the swap partition, which messes up
> the other operating systems on the device, because the recent 'best
> practice' has been to identify partitions in fstab by UUID.

Did it really? Good - so it should!! If you selected using that existing
swap volume, I think that it's a reasonable default for it to format it.
Same goes for any other volume except /home.  If you had reason to not
want it formated then you should have to mark it to not be formatted.

This protects you from situations where you do a new install re-using
the existing partition/volume layout and an ensures that any old
suspend2disk data in the swap is wiped out preventing a corruption
resulting from the next reboot from trying to restore from the stale
suspend image.

I'm sure that the installer only would do this if you chose to set that
partition up as swap in the first place.  Given that suspend2disk uses
the swap volume I'd recommend never using the same swap space for
different linux systems anyway in a multi-boot setup.

-- 
Daniel Reurich
Centurion Computer Technology (2005) Ltd.
021 797 722



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Re: [DNG] installer messes up swap partition on multi-boot

[Boruch Baum]

Bad suggestion, Adam. I don't know that the debian installer acts that
way. The issue is that the devuan installer is deciding on its own to
re-format an existing swap partition.

On 03/21/2016 05:17 PM, Adam Borowski wrote:
> On Mon, Mar 21, 2016 at 04:29:47PM -0400, Boruch Baum wrote:
>> On today's install device, I had a pre-existing linux with a swap
>> partition on the disk, and the partitioner insisted on re-formatting it.
>> This is BAD. It changes the UUID of the swap partition, which messes up
>> the other operating systems on the device, because the recent 'best
>> practice' has been to identify partitions in fstab by UUID.
>>
>> It significantly slows the boot of those other linuxes, and they lose
>> their swap, and the sysadmin has to manually fix the fstab.
> 
> As your problem is not specific in any way to Devuan, I suggest reporting it
> upstream, ie, in Debian.
> 


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Re: [DNG] installer messes up swap partition on multi-boot

[Adam Borowski]

On Mon, Mar 21, 2016 at 04:29:47PM -0400, Boruch Baum wrote:
> On today's install device, I had a pre-existing linux with a swap
> partition on the disk, and the partitioner insisted on re-formatting it.
> This is BAD. It changes the UUID of the swap partition, which messes up
> the other operating systems on the device, because the recent 'best
> practice' has been to identify partitions in fstab by UUID.
> 
> It significantly slows the boot of those other linuxes, and they lose
> their swap, and the sysadmin has to manually fix the fstab.

As your problem is not specific in any way to Devuan, I suggest reporting it
upstream, ie, in Debian.

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[DNG] installer messes up swap partition on multi-boot

[Boruch Baum]

On today's install device, I had a pre-existing linux with a swap
partition on the disk, and the partitioner insisted on re-formatting it.
This is BAD. It changes the UUID of the swap partition, which messes up
the other operating systems on the device, because the recent 'best
practice' has been to identify partitions in fstab by UUID.

It significantly slows the boot of those other linuxes, and they lose
their swap, and the sysadmin has to manually fix the fstab.

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