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#1 2022-08-31 14:04:15

Registered: 2022-01-10
Posts: 3

systemd-cryptsetup very slow on boot

During boot, unlocking the encrypted boot partition is very slow:

# systemd-analyze blame
14.579s systemd-cryptsetup@cryptboot.service

Checking some things doesn't reveal any issues on the running system:

# time cryptsetup luksOpen --test-passphrase --verbose /dev/nvme0n1p2
Enter passphrase for /dev/nvme0n1p2: 
Key slot 0 unlocked.
Command successful.
0.25s user 0.01s system 7% cpu 3.503 total

# time cryptsetup luksOpen --test-passphrase --verbose --key-file /etc/bootkey /dev/nvme0n1p2
Key slot 1 unlocked.
Command successful.
0.48s user 0.00s system 93% cpu 0.514 total

And this is how the LUKS setup looks like:

# cryptsetup luksDump /dev/nvme0n1p2
LUKS header information for /dev/nvme0n1p2

Version:        1
Cipher name:    aes
Cipher mode:    xts-plain64
Hash spec:      sha256
Payload offset: 32768
MK bits:        512
MK digest:      74 5f 7d 2e 7f 13 20 cd 3e 75 1f 11 a8 fa e9 9b 1c b9 62 68 
MK salt:        b9 60 4f f6 87 3c 01 4a 0d 2e b3 e7 56 ae d3 8c 
                6f 16 5b bb a5 ff b4 31 c3 ab d9 0a 43 4f d3 c1 
MK iterations:  385505
UUID:           78ef6142-143f-4e67-911c-044c1bf67dfb

Key Slot 0: ENABLED
        Iterations:             500000
        Salt:                   a0 49 36 1a 2f c7 97 c8 f5 3a 3f d6 6f 8f 29 00 
                                61 eb a5 f3 6b ee 07 ff bc 6e 48 2f 15 98 47 7c 
        Key material offset:    1016
        AF stripes:             4000
Key Slot 1: ENABLED
        Iterations:             500000
        Salt:                   bf 4f 4f 55 34 d9 92 96 6d 75 2f db 2d 22 dc a3 
                                8a f5 a5 3d 97 80 52 b0 92 73 41 05 07 f8 f6 68 
        Key material offset:    8
        AF stripes:             4000
Key Slot 2: DISABLED
Key Slot 3: DISABLED
Key Slot 4: DISABLED
Key Slot 5: DISABLED
Key Slot 6: DISABLED
Key Slot 7: DISABLED

LUKS v1 because of GRUB... And GRUB is relatively fast in unlocking this partition (2-3s).

Any idea what I could do to bring the "systemd-cryptsetup@cryptboot.service" down to a few seconds?


#2 2022-09-01 04:03:47

From: Cymru
Registered: 2011-11-27
Posts: 6,241

Re: systemd-cryptsetup very slow on boot

The systemd-analyze blame output isn't really comparable to the others because decrypting boot may be waiting on other things to finish first, whereas in all the other cases, decrypting boot is the only thing being done.  So it isn't clear there's anything here to solve. Unlike GRUB, systemd is just piggybacking on the standard cryptsetup etc., as far as I know.

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