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I recently installed Debian 10 on my laptop and for the first time I decided to give file encryption a go. But I've found something interesting in the /etc/fstab file, and it's that it doesn't use UUID and instead it uses absolute paths.

This is my /etc/fstab:

# <file system>  <mount point>  <type>  <options>  <dump>  <pass>
/dev/mapper/sda1_crypt    /        ext4    errors=remount-ro    0    1
# /boot was on /dev/sda3 during installation
UUID=fb4bd462-2ad8-4e56-b84e-602a94bf8b31   /boot  ext4  defaults 0   2
/dev/mapper/sda5_crypt    none     swap      sw    0     0

And this is the output from lsblk -o PATH,UUID,NAME,MOUNTPOINT

NAME     PATH                   UUID                  MOUNTPOINT

sda      /dev/sda                                                    
├─sda1   /dev/sda1              f0ece3a3-69c2-4ad8-b819-311a18c37b21 
│ └─sda1_crypt
│        /dev/mapper/sda1_crypt b73f7cef-ba4e-4587-9dba-da8385d93824 /
├─sda2   /dev/sda2                                                   
├─sda3   /dev/sda3              fb4bd462-2ad8-4e56-b84e-602a94bf8b31 /boot
└─sda5   /dev/sda5              ca96319f-82b3-4cbf-a1e1-7d30f7be4576 
  └─sda5_crypt
         /dev/mapper/sda5_crypt 40b9e71c-46b5-4d29-91a4-aaa12ca0e109 [SWAP]

I have an encrypted root partition on sda1 and an encrypted swap partition on sda5. I had to create an unencrypted /boot partition too (sda3). sda2 is free space I'll use for other purposes.

As you can see in the /etc/fstab, Debian identifies my /boot partition with its UUID, as it did on other occasions that I installed an unencrypted system, but it uses absolute paths for the encrypted partitions.

Can anyone help me identify why this happens and if it would be a good idea or even a good practice to change the /etc/fstab file so it uses UUID instead of paths?

Thanks.

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  • You are correct that this is not the best practices. Does your /etc/cryptab reference the partition by UUID? ALso, is it possible for you to set up your partitioning scheme using LVM? LVM is not necessary but I find helpful for better managing my partitions in general, especially if I am encrypting them.
    – kemotep
    Commented Nov 1, 2019 at 15:30
  • Thanks for your answer. Yes, my /etc/crypttab uses UUIDs, so I think everything should be alright. I didn't know about /etc/crypttab file before this so I thought that /etc/fstab was everything there was.
    – 3435
    Commented Nov 4, 2019 at 14:37

1 Answer 1

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These absolute device paths are perfectly fine, since their names are stable and prescribed by the first fields in the lines of /etc/crypttab. Actually, they are symlinks to the numbered (thus unstable) device mapper device node names. If /etc/crypttab refers to their source devices (in the second fields) by stable names or UUIDs, your are safe from unpredictable device ordering.

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