[linux-lvm] [Bulk] Re: lvm protected against crypt/luks

[lejeczek]

On 08/03/16 11:12, Bryn M. Reeves wrote:
> On Mon, Mar 07, 2016 at 03:03:10PM -0500, John Stoffel wrote:
>> lejeczek> Do I need to wipe block devices clean off any LVM traces in
>> lejeczek> order to encrypt them?
>>
>> No... but it's probably a good idea to do so initially, which is
>> really to just zero it out. But LV information is stored within the
>> VG, which is stored within the PVs which make it up.
> Better to overwrite it with garbage (/dev/urandom for e.g.). This can
> take a very long time for large volumes but makes attacks on the
> ciphered data harder.
>
> The Arch wiki has some discussion of this:
>
>    https://wiki.archlinux.org/index.php/Dm-crypt/Drive_preparation
>
> You also need to decide where you want the encrypted layer to sit:
> you can encrypt PVs (meaning that the entire volume group using
> those PVs is encrypted), or you can encrypt individual LVs.
>
> The choice depends on what you want to protect and how much of a
> performance penalty you are willing to take for the encryption.
>   
>> Of course they can.  Then you just loop mount the encrypted LUKS
>> device (physical disk or LV, or even a file) and then put a filesystem
>> on the new device.  Then you mount that filesystem and away you go.
superb, thanks chaps,
on keyfiles, would you know why this:

cryptsetup luksOpen /dev/h300Int1/0 h300Int1.0_crypt 
/etc/crypttab.key --keyfile-offset 12

won't work? Whenever I use offset, I will not get:
Key slot 0 unlocked.
Command successful.

thanks.

> No need for loop devices or mounts - a dm-crypt layer looks just
> like a regular linear device-mapper device and can be mounted or
> passed to tools like mkfs just like any other.
>
> The only extra things you have to deal with are the rather long
> UUID-based names that luks uses by default and the need to give
> the passphrase or key to unlock the device at boot or activation
> time - there are mechanisms integrated in most modern distros to
> assist with this either via configuration files or interactive
> prompts.
>
> Again, Arch have a pretty good overview in their wiki:
>
>    https://wiki.archlinux.org/index.php/Dm-crypt
>
> Regards,
> Bryn.
>
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