[dm-crypt] Can LUKS be used on a tmpfs?

[dm-crypt] Can LUKS be used on a tmpfs?

[H McCurdy]

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Hi,
Is it possible to get crypt_init() to use a tmpfs instead of a block device or a file?
I realize there are sanity issues related to such an inquiry because the key is in RAM and so is the "disk."  Regardless, I have the question.
BTW, an older ramdisk (/dev/ram0) does appear to work.
Hugh

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Re: [dm-crypt] Can LUKS be used on a tmpfs?

[Michael Kjörling]

On 23 Dec 2015 19:05 +0000, from hmccurdy@yahoo.com (H McCurdy):
> Is it possible to get crypt_init() to use a tmpfs instead of a block
> device or a file?

Not sure exactly what you are looking to do, but you can't put a tmpfs
on any storage-backed device. You could however create a temporary
(likely sparse) file, store that file in a tmpfs, and create a LUKS
container within that file, with a normal file system inside the
container which you can use to store data.

Would be quite a lot of overhead, though. And you need to be root to
mount a tmpfs in the first place, unless you set it up in fstab with a
"user" directive, which would sort of defeat the point.

Isn't it easier to just set appropriate permissions on a tmpfs (or
even ramfs, which would prevent ever writing the data to disk)? You'd
get pretty much the same results, minus virtually all the overhead...

-- 
Michael Kjörling • https://michael.kjorling.se • michael@kjorling.se
                 “People who think they know everything really annoy
                 those of us who know we don’t.” (Bjarne Stroustrup)

Re: [dm-crypt] Can LUKS be used on a tmpfs?

[Sven Eschenberg]

Simply short: No.

tmpfs is, as the name suggests, a filesystem, which lives in the VFS 
domain, whereas dmcrypt lives in the block layer.

So yes, ramdisks in the form of blockdevices will work. It might even 
possibly work on a file within the tmpfs. (Give is a try [there's still 
loopback devices..], afterall it's all volatile memory and fiddling 
around does not need any extra work)

Regards

-Sven


Am 23.12.2015 um 20:05 schrieb H McCurdy:
> Hi,
>
> Is it possible to get crypt_init() to use a tmpfs instead of a block
> device or a file?
>
> I realize there are sanity issues related to such an inquiry because the
> key is in RAM and so is the "disk."  Regardless, I have the question.
>
> BTW, an older ramdisk (/dev/ram0) does appear to work.
>
> Hugh
>
>
> _______________________________________________
> dm-crypt mailing list
> dm-crypt@saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt
>

Re: [dm-crypt] Can LUKS be used on a tmpfs?

[Milan Broz]

On 12/23/2015 08:05 PM, H McCurdy wrote:
> Hi,
> 
> Is it possible to get crypt_init() to use a tmpfs instead of a block
> device or a file?

No, dm-crypt works only over block devices (/dev/ram* are block devices as well).

You can create a file on tmpfs and use that through loopback though
(but this adds another layer there).

Milan