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Encrypted flash drives

Hello the list!

This is a problem of repairing an encrypted USB drive that isn't playing 
nice with Gnome after setup although it is basically working and no data 
has been lost.

Today I opened my desk drawer and found the USB flash drive I have used 
to back up my GPG private keys, revokation keys etc had _something 
sticky_ growing on it. Not nice. And bizarre because nothing around it 
in the drawer was affected.

So I bought 2 identical relatively small new USB drives, with the intent 
of copying the content of the 
rapidly-becoming-unfit-for-human-consumption drive onto both of them, 
and keeping one offsite. And this seemed like a great time to make my 
first experiment with volume encryption.

I'm running Jessie and Gnome on the desktop, so my machine's default 
behaviour when I plug in a flash drive is to pop up a, erm, pop-up 
asking if I want to open the drive in Files (nautilus) or eject it. I 
clicked Open with Files. Next I right-clicked on the drive in the left 
pane and chose "Format..." To my rather pleasant surprise support for 
encrypting the volume was right there in the Format dialog. I proceeded 
to provide a label and passphrase for the drive and went through the 
confirmation stages warning me I was about to lose data and so on.

Then, nothing apparently happened. Turns out it was creating the ext4 
file system in the just-created encypted volume, but it didn't _say_ 
that, and I thought it was done, and had unmounted the volume, so I 
removed it. D'oh!

I've filed a bug on Files for that because although I was stupid to 
remove the device without doing SOMETHING to check if it was still being 
used, the fact is Files gave me zero feedback that it was doing 

After this Files couldn't do anything with the drive so I dropped to the 
command line. There I executed the following as root:

cryptsetup luksFormat /dev/sdg1

(for 'twas /dev/sdg1 where the now-messed-up drive was). This completed 
successfully, asking me for the passphrase on the way. Then:

cryptsetup luksOpen /dev/sdg1 SECRETKEY1

Which also completed successfully. Finally:

mkfs.ext4 /dev/mapper/SECRETKEY1

which took a bit longer to complete than I expected, but eventually 
completed successfully. That was what tipped me off to what I had done 
wrong in the first place in Files.

After this, I ejected the device, and plugged it back in. Gnome does not 
respond, but if you manually start Files, you can see "8.1GB Encypted" 
in the left hand pane. Clicking on that triggers the request to supply 
the password and on correctly supplying the password you have access to 
the device. However, can't write to it, and I have to drop to the 
command line and su to root before I can do so.

I then used Files to format and encrypt the second device, and this time 
was more patient to wait until it was finished, at which point the 
device was mounted with the label I'd chosen and I could safely eject it 
the normal way. After this, re-inserting the second device is 
automatically detected by Gnome and I am prompted for the password, and 
on supplying it, I get the usual "Open in Files or Eject" prompt and 
everything operates after that as if it were not encrypted, including 
non-root writes.

With both drives mounted, I compared the /etc/mtab entries for the two 
and this is what I found:

/dev/mapper/luks-378947be-2ef0-452e-8d80-04064aec5bc7 /media/mark/138b9d59-b0cd-49cc-a738-8fecea5f0035 ext4 rw,nosuid,nodev,relatime,data=ordered 0 0
(that's the first drive, that I used the command line to fix after 
messing it up in Files)

/dev/mapper/luks-0dfd326a-10ea-4f1f-8ca3-4ab492ebd62e /media/mark/SECRETKEY2 ext4 rw,nosuid,nodev,relatime,data=ordered 0 0
(That's the second one that everything works properly for).

>From here, how can I fix the first one to play nice? (Wiping it and 
re-formating from scratch is an option, but I figure I will learn more 
from fixing it)