[EdLUG] Linux hibernate

[Roy]

Isn't the hibernate image compressed these days?

That means that it might fit with some swap in use. It might not too.

Regards,

Roy Bamford



On 17/09/2022 16:50, Geetam wrote:
> I only know the theory of hibernating, so please fill in a bit of 
> hibernating knowledge that I do not have. (I am so old-fashioned that 
> I shut down and boot up 😬 )
>
> When hibernating, the state of internal memory is stored on disk. 
> Linux uses the swap partition on disk for this. So your swap partition 
> needs to be large enough, i.e. at least as large as your internal 
> memory - in your case 32Gb
>
> BUT WHAT HAPPENS when you have so much open on your desktop that your 
> internal memory wasn't big enough and some of the less active 
> processes have been swapped to swap space? (I am sure most of us avoid 
> that, but that is what swap space is for, isn't it?)
>
> Say you have 40GB in use (32Gb in internal memory, 8Gb swapped to swap 
> space). Is hibernating going to try to save 40GB into swap space? That 
> won't fit into the 32Gb swap partition... Or is it only writing the 
> 32Gb in internal memory to the swap partition clobbering the 8Gb that 
> was there? Then the full state of your desktop cannot be restored.
>
> Is this maybe why Andrew is not able to hibernate?
>
> I am sure someone in the Linux world has thought about this, but I 
> think we have forgotten because we try to have so much internal memory 
> that swaps space is not used and the issue hardly ever arises these 
> days. Still, I am curious 🤔
>
> Regards
> Geetam
>
> -- 
> I don't know
> ...
> I don't know what it is
> ...
> I don't know what it is that I don't know
>
> Isn't it beautiful
>
>
> On Fri, 16 Sept 2022 at 08:04, Colin Shorts <colin.shorts at gmail.com> 
> wrote:
>
>     Hi Andrew, I'd be inclined to add a smidgen more swap to be on the
>     safe side.
>
>     I take it `sudo pm-hibernate` doesn't work (correctly) either? Are
>     the kernel parameters getting set at boot (I think dmesg should
>     say which device will be used)? Is your swap partition on lvm, are
>     you mounting it using the uuid?
>
>     I'm in the middle of redecorating my home office or I'd give it a
>     bash myself 😃
>
>     Cheers,
>     Colin
>
>     On Fri, 16 Sept 2022, 01:16 Andrew Smith, <asmith9983 at gmail.com>
>     wrote:
>
>         Hi Colin
>         I have 32Gb of swap, with /htop/ reporting none used in normal
>         operation.
>         Suspend works OK. Given the minimal energy consumed overnight
>         on suspend, I may just continue using that until I can
>         investigate further  how /suspend-then-hibernate/ is meant to
>         operate by reading the sourcecode of /systemctl. /
>         Andrew
>
>
>         On Wed, 14 Sept 2022 at 20:07, Colin Shorts
>         <colin.shorts at gmail.com> wrote:
>
>             I'm no expert on hibernate (I use suspend myself), but
>             iirc you'll need at least as much free swap as system ram
>             +used swap. 64GB doesn't sound unreasonable as a starting
>             point assuming you've got enough space and considering how
>             much Chrome can chew up.
>
>             -Colin
>
>             On Wed, 14 Sept 2022, 18:03 Andrew Smith,
>             <asmith9983 at gmail.com> wrote:
>
>                 Guys
>                 For quite a while, I've been putting my system into
>                 suspend mode, which was successful , apart from an
>                 odd occassion. I now want to try saving more energy
>                 I've tried powering down, but would like it to restart
>                 in the same state rather than with a new login, as I
>                 had with suspend.
>                 I've tried "systemctl suspend-then-hibernate" from
>                 root CLI, but  I get essentially  a fresh boot.
>
>                 Any suggestions ?
>                 I'm running kernel 5.4.0-125-generic from Ubuntu, in
>                 32Gb RAM, and typically have a around hundred tabs
>                 open on Chrome.
>                 Andrew
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