Solved, see below.
I recently reinstalled my home server and was unable to open my LUKS-encrypted hard drive. Neither my usual passphrase nor a newly created keyfile were working. I tested on different distros, initially on my new Proxmox installation, later on a the Arch ISO. I eventually tried the disk on my main system, on which it used to be and I still had an old keyfile on - et voilá. So I created keyfiles as suggested in the wiki and occasionally md5sum returned a different hash for the keyfile! Why is this happening? I find' this extremely concerning because this could potentially result in massive data loss due to a keyfile apparently randomly not working as I was experiencing it. What am I missing?
For reference because I don't know how to share what I exactly did.
Scenario #1:
A directory on a mounted hard drive on my desktop.
$ echo -n '$mypassphrase' > ./dir/keyfile
$ md5sum ./dir/keyfile
c6dd9329dbe030127ce5e19d85de4df9 ./dir/keyfile
# chown root:root ./dir/keyfile; chmod 400 ./dir/keyfile
# md5sum ./dir/keyfile
c6dd9329dbe030127ce5e19d85de4df9 ./dir/keyfile
Scenario #2:
My old keyfile in /etc on my desktop containing $mypassphrase.
# md5sum /etc/keyfile
a1c10c2d023c982259f6c945ebee664e /etc/keyfile
Scenario #3:
Booted from the Arch ISO on my server.
# echo -n '$mypassphrase' > keyfile
# chown root:root keyfile; chmod 400 keyfile
# md5sum keyfile
c6dd9329dbe030127ce5e19d85de4df9 keyfile
Scenario #4:
A directory in /home on my desktop.
$ echo -n '$mypassphrase' > ./keyfile
$ md5sum keyfile
a1c10c2d023c982259f6c945ebee664e keyfile
EDIT: I just moved the disk back into my server and tried echo'ing my passphrase into a keyfile which returned the hash starting with c6, whereas opening a file using nano and pasting the passphrase into the file returned the hash starting with a1.
EDIT: I moved the disk back into my server, reinstalled Proxmox and tried again. I was able to unlock the disk after I pasted the passphrase into a file and deleted all trailing spaces/newline. I also tried echo'ing the passphrase into a keyfile and that also did not work, no clue why but it seems to work on some systems on not on others.
Perhaps do it with the string "test" and post results so we can replicate.
Could it be a character encoding issue? Are you using utf-8 on both machines?
locale charmapto check (other ways: https://stackoverflow.com/questions/5306153/how-to-get-terminals-character-encoding )Thanks for your answer. I'm using UTF-8 on my desktop running Arch Linux and my server running Proxmox.
$ echo -n 'myrandompassphrase123' > keyfile$ md5sum keyfile49b3cdce58e65935b8255438266dd87e keyfileWhereas editing the keyfile using nano and pasting 'myrandompassphrase123' returns 59be855b925013d35476e82763b7a80e.
This is the scenario that's the least concerning, because I get that echoing into a file and editing a file using nano could yield different results. Unfortunately (or luckily) I can't reproduce the 4th scenario, which concerned me.
I suspect you can't replicate scenario 4 because it was never a thing (Pretty natural to skip over something by accident). A trailing newline was my first thought, but scenario 4 ruled it out. If you can't replicate it then it's the likely answer.
Something like this would confirm
echo "$mypass" | md5sumVs
echo -e "$mypass\n" | md5sumI'll have a play tomorrow and see what I get.
I suspect opening up the two files in a hex editor will show the difference, assuming I can replicate your results.