[dm-crypt] Cryptsetup FAQ montly pointer 8/13

Arno Wagner arno at wagner.name
Sat Aug 3 23:47:15 CEST 2013

On Sat, Aug 03, 2013 at 10:47:25PM +0200, Milan Broz wrote:
> On 3.8.2013 19:57, Arno Wagner wrote:
> >>For plain crypt (or Truecrypt) you have no UUID, so you cannot use it.
> >>(You can use uuid/wwid of underlying device as mentioned above
> >>but this is not be present always.)
> >
> >Indeed. I tried both when I wrote the entry, only to find that
> >neither worked on my system (Debain with custom kernel).
> >
> >As this is not a distrioution specific FAQ (there are those)
> >distribution specific stuff shopuld not go into it. Of course
> >documentation for a specific distribution can contain specific
> >advice that is not general, and some people have already asked
> >me about such things, also with regard to encrypted swap.
> Device UUID/model etc should not be distribution specific,
> udev /dev/disk/by-id* is quite standard among distibutions here.

I thought so too, but the only thing I have in my /dev/disk/by-id
are my raid devices, nothing else, and I do have normal partitions.
> In fact, udev reads it directly from /sys attributes, as the same
> as lsblk does.

lsbkl works. I have no idea what is wrong here, but unless I 
damaged it on two different systems without noticing, it does 
not seem to be universal. Maybe something wrong in my kernel 

> Maybe FAQ should also note that kernel device names (sda/sdb etc) is
> NOT generaly persistent between reboots. (Usually it is the same but
> nothing guarantees it, e.g. plugged USB disk or new SATA card can change
> ordering and names). This is important mainly if you use swap keyword
> whis is formatted on boot.

I have that in there, but maybe not clear enough. Added more.

Anyways, thanks to everybody for the feedback! Its great
that some people actually read the stuff I write!

Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
There are two ways of constructing a software design: One way is to make it
so simple that there are obviously no deficiencies, and the other way is to
make it so complicated that there are no obvious deficiencies. The first
method is far more difficult.  --Tony Hoare

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