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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

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Need help with setting up full disk encryption (FDE) where /home is on another drive. (lemmy.world)

submitted 15 hours ago* (last edited 15 hours ago) by [email protected] to c/[email protected]

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Any distro would do, but for my case, it is Arch because I have more control over the partitions. I would like the OS, so root, swap and others on 1 drive. The /home should be on a separate drive. The tricky thing is to have everything encrypted, except /boot and /efi of course.

Now, here is what I can do

FDE on 1 drive. This is easy: you create /efi, /boot and then create a large LUKS partition. From there, you create LVM on that LUKS partition and get your: /, /home and swap. Then mount everything correctly and install.

In the grub config, you only need to set it so it knows the LUKS partitom and where the root is. For eg, if your LUKs partition is /dev/sda3, you do:

cryptdevice=UUID=<uuid of the /dev/sda3>: cryptlvm rootfs=/dev/vg/root.

Unencrypted /home on another drive. This is like 1) but /home is mounted on a separate drive. Still need to do the grub config, but nothing is needed for /home. It is automatically mounted when you login.

Now for my case: Encrypt /home

The encryption and mount part is easy. But how to get the OS to recognize it? The Arch wiki has this weird thing where you create an encryption key, they called it home.key, using cryptsetup. You then store the key in /etc and then in your /etc/crypttab, you specifiy the drive with /home and location of the key. No need for any passphrase.

The problem I have with this is that keys are stored in root. So if my root system is corrupted, I cant even decrypt home....

Any advice is welcome..

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[–] [email protected] 0 points 14 hours ago (1 children)

yeh if I encrypt /home using luks with passphrase, so cryptsetup. How do I tell the OS to decrypt it? I tried passphrase before and it cannot boot because /home cannot be mounted. That is why I searched and found out about the Arch wiki way: using keyfile stored in root.

[–] [email protected] 8 points 14 hours ago* (last edited 14 hours ago) (2 children)

LUKS does offer multiple key slots. You can have the OS unlock it with a keyfile and be able to manually unlock it with a keyphrase when you don't have access to that file.
I'm not sure if you can tell the OS to unlock it with a passphrase on boot like with the root partition.

[–] [email protected] 1 points 8 hours ago

That's the simplest answer.

[–] [email protected] 2 points 10 hours ago (1 children)

You can.

[–] [email protected] 1 points 36 minutes ago

I honestly can't remember the details, but I followed an Arch guide somewhere (probably the wiki). It definitely prompts me for passphrase on boot.