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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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Warning: ubuntu tpm recovery key cannot unlock disk outside of boot (self.linux)

submitted 11 months ago* (last edited 11 months ago) by ichbinjasokreativ to c/[email protected]

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Hi everybody, bit of a warning here: The recovery key generated during the installation of Ubuntu 23.10 (if you select tpm-backed fde) cannot be used to unlock the disk outside of boot, as in any 'cryptsetup' command and so on will not accept the recovery key. unlocking when accessed from different system does not work etc.

You can use it to unlock the disk while booting if your tpm somehow fails, but ONLY in that specific situation.

I kind of purposefully broke my tpm keys to see if it could be restored with 23.10 and ended up having to reinstal, as I ended up having to enter the recovery key at boot every time and no way of adding additional unlock options to the volume, as cryptsetup would not accept the recovery key as passphrase.

This bug could be very bad for new users.

See this bug report: https://bugs.launchpad.net/ubuntu-desktop-installer/+bug/2039741

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[–] ichbinjasokreativ 1 points 11 months ago

the tpm basically gets registered as a valid way to decrypt the luks partition that all your data is in. It does so by first checking if the system is authorized to receive the keys. If the key in the tpm gets deleted or invalidated, or if the system signature changes because of a firmware update (shouldn't really happen), then the tpm will no longer unlock the partition. I'm no expert either though, just how I understand it. TPM-backed Full Disk Encryption has become more mainstream after microsoft made it a requirement for windows 11 and the option is right there in the installer, it's also one of the selling points of 23.10. Yes, it's clearly marked as experimental, but people will do what people do and thus they should know of the recovery key issue. Currently, if your tpm does not unlock your partition, you HAVE to enter the recovery key every time you boot, or reinstall Ubuntu.