Re: how to enable trim for an external encrypted SSD?

[Christian Seiler <christian@iwakd.de>]

Hi again,

A quick follow-up, because cryptsetup 2.0.0 was recently released:

On 11/06/2017 02:28 PM, Christian Seiler wrote:
> And while you might be able to reconfigure udisks to pass the discard
> option to cryptsetup (though I'm also doubtful about that), that
> configuration would have to happen on each individual computer, and
> can't be put onto the external drive.

The new LUKS2 header format (requires cryptsetup 2.0.0) does support
this, the release announcement specifically mentions discards as a
feature option:

Quoting
<http://www.saout.de/pipermail/dm-crypt/2017-December/005771.html>:

  * Persistent flags
    The activation flags (like allow-discards) can be stored in
    metadata and used automatically by all later activations (even
    without using crypttab).

    To store activation flags permanently, use activation command
    with required flags and add --persistent option.

    For example, to mark device to always activate with TRIM
    enabled, use (for LUKS2 type):

     $ cryptsetup open <device> <name> --allow-discards --persistent

    You can check persistent flags in dump command output:

    $ cryptsetup luksDump <device>

Doesn't help you directly because of the problems you've described
with your USB adapter not forwarding TRIM commands properly, and
this feature will not be part of Debian before the release of
Debian 10/Buster (I hope at least ;-)), but I still wanted to
mention this in case anyone stumbles over this thread in the
mailing list archives.

Regards,
Christian