[GTALUG] Thinkpad [3]: Aligning size of dm-crypt and partition/filesystem

Thu Jun 16 11:38:58 EDT 2016

On Wed, Jun 15, 2016 at 11:59 PM, Allan Zhang <allan at azic.ca> wrote:

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> Matt,
>
> just curious, is there any reason you chose a MBR +UEFI boot?
>

> Surely your laptop came with Windows, which mandates that GPT accompanies
> UEFI.
>

I think because this was (is!) my first UEFI laptop and I was unfamiliar
with GPT when I first partitioned the disk. I wiped windows right away so
tha wasn't an issue for me.  It was also my first Arch install, so there
were a number of unfamiliar elements, and I stuck to what I knew where I
could.

>
> Could you have used your M.2 for swap?
>

I certainly expected to. On boot, the kernel seemed to have trouble finding
the M.2 device, and I couldn't immediately tell what the problem was, so it
seemed easiest to make space on the old drive and put the swap there.

>
> As for suspend to RAM, aka regular suspend, I find my Thinkpad does not
> live for too long (a few hours) in this state, evident by the "i" LED not
> blinking anymore. It's very strange that you have to remove the battery
> though.
>

I don't think those two issues are the same. The battery doesn't drain out
on my laptop; instead, I think something goes wrong in the electronics of
the power circuitry. I'm not sure what causes it but there are reports of
similar behaviour online.

>
> Also, wouldn't suspending to RAM defeat the purpose of your encrypted disk?
>

...  yeeeeesssss...  though since I'm not encrypting the suspend2disk image
either, that is at least as big an issue as s2ram, I suppose.  In general
it seems to me that best practices are still hard to implement fully unless
you're willing to devote a fair amount of time to develoing the necessary
expertise.

- -------- Original Message --------

> From: Matt Price via talk <talk at gtalug.org>
> Sent: June 15, 2016 9:22:13 PM EDT
> Cc: GTALUG Talk <talk at gtalug.org>
> Subject: Re: [GTALUG] Thinkpad [3]: Aligning size of dm-crypt and
>  partition/filesystem
>
> On Wed, Jun 15, 2016 at 5:59 PM, o1bigtenor <o1bigtenor at gmail.com> wrote:
>
> > On Wed, Jun 15, 2016 at 9:43 AM, Matt Price via talk <talk at gtalug.org>
> > wrote:
> > > Final question! In order to enable suspend to disk, I ended up
> shrinking
> > my
> > > root partition (I also added an M.2 SSD, so the whole thing was a bit
> > > complex). In the end I got it to work, but I made some kind of an error
> > and
> > > currently my on-disk “crypt” is a little larger than the partition and
> > file
> > > system that I am using for root, so I have some wasted space on the
> disk:
> > >
> > > ➜  ~ sudo fdisk /dev/sda
> > >
> > > Command (m for help): p
> > > Disk /dev/sda: 238.5 GiB, 256060514304 bytes, 500118192 sectors
> > > Units: sectors of 1 * 512 = 512 bytes
> > > Sector size (logical/physical): 512 bytes / 512 bytes
> > > I/O size (minimum/optimal): 512 bytes / 512 bytes
> > > Disklabel type: gpt
> > > Disk identifier: 9B4C2E92-6C7D-4C69-B67B-1823E4DB9BA6
> > >
> > > Device         Start       End   Sectors   Size Type
> > > /dev/sda1       2048   1026047   1024000   500M EFI System
> > > /dev/sda2    1026048 106907647 105881600  50.5G Linux filesystem
> > > /dev/sda3  106907648 483340287 376432640 179.5G Linux LVM
> > > /dev/sda4  483340288 500117503  16777216     8G Linux swap
> > >
> > > ➜  ~ sudo cryptsetup status cryptsetup
> > > /dev/mapper/cryptsetup is active and is in use.
> > >   type:    LUKS1
> > >   cipher:  aes-xts-plain64
> > >   keysize: 256 bits
> > >   device:  /dev/sda2
> > >   offset:  4096 sectors
> > >   size:    105877504 sectors
> > >   mode:    read/write
> > >
> > > Anyone out there have advice abot how to safely and reliably expand the
> > > partition and the file system so that they both end precisely where the
> > > crypt does?
> > >
> > > Thanks again guys! as always, it’s much appreciated.
> > >
> >
> > No ideas on the other two problems but on this one I would recommend
> > using something like:
> >
> > boot your system using a system rescue disc
> >
> Yes! I use the Ubuntu livecd just because it's easy to get
>
> > adjust your partition(s)  (carefully please) using gparted
> >
> is that adequate? Can I be sure that the crypt and the partition match
> exactly? I feel like it's somewhat difficult to measure the size & extent
> of a crypt in units that gparted also understands
>
> > close
> >
> > reboot as regular
> >
> > Should be real easy (assuming that the empty space is right beside
> > where you want it.
> > Recommend a backup before but then you already know that - - yes?
> >
> yes... though I don't always follow recommendations.
>
> >
> > Let us know what you use
> >
>
>
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