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Date: Mon, 27 Jul 2015 21:49:43 +0200
From: Milan Broz <gmazyland@gmail.com>
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Subject: Re: [dm-crypt] persistent naming: add ID in addition to UUID
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To: ilf <ilf@zeromail.org>, dm-crypt@saout.de

On 07/27/2015 09:26 PM, ilf wrote:
> Sven Eschenberg:
>> Since you want to use crypttab anyway, is there any particular reason not 
>> to use /dev/disk/by-id/<identifier>?
> 
> You are comlpetely right, that works and I should probably use that.
> 
>> As UUID=<uuid> needs proper symlinks anyway, it is rather a handy 
>> shorthand at the commandline.
> 
> Well, the man-page for crypttab(5) in Debian and Derivatives sais, "the 
> UUID is supported as well, using UUID=<luks_uuid>". So adding an ID= 
> option would make this more consistent.

Actually I added UUID=<..> to cryptsetup to mainly easily implement
scripts doing the similar action as fstab/crypttab UUID= mount.
(fstab allows LABEL and UUID but not ID; also LUKS has no label)

Not sure if adding ID is worth to do this, it is really just
shortcut to udev symlink. Note that UUID is read from header and has
always the same format.

ID can be crazy combination of characters, sometimes even dynamic
(not everything is hw-serial based, see DM devices for example).
(I remember several bugs for multipath/SCSI devices where hw-based ID contains
binary data and must be properly escaped for symlink name...)

Milan