Possibly a silly question. I have my hard drive encrypted so on turning on my laptop I have to enter my hard drive password. There is nothing else on this screen. If I wish to shut down my computer at this point what is the safest way off doing it?

I would hope there is a way of doing it without having to login and then having to shutdown.

Running 14.04 on my machine. It has 2 hard drives; one for Ubuntu and the other for /home. There is only full disk encryption on the OS Hard Drive.

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    If you're using full-disk encryption, then you can be sure nothing is being written (since you haven't decrypted the drive). As such a hardware power-off (eg hold the power button) should be entirely safe. If you are only encrypting (for example) /home (doesn't sound like it), it's a bit trickier – Darael Nov 20 '15 at 12:15
  • @Darael Have 2 hard drives. Will edit question to update. – gman Nov 20 '15 at 12:30
  • If the FDE is on the OS drive, as you say, you can still be sure nothing is being written, because the OS can't mount the /home drive (or even know that it would need to mount it) until said OS is decrypted! – Darael Nov 20 '15 at 12:36
  • If the FDE is on /home (just for reference), it's a mite trickier. I'd be inclined to use the Magic SysRq sequence REISUO in that case, with multi-second pauses between each. It's almost certainly not the best option for that situation, though - just the first thing to spring to mind. – Darael Nov 20 '15 at 12:43

As you are using full-disk encryption on the OS drive, and you have not yet entered the password to decrypt that disk, you may be sure that nothing is being written there. You can also know that nothing is being written to the disk containing /home, as without decrypting the OS drive the system can't access /etc/fstab and thereby discover that it needs to mount /home, let alone actually mount it.

As such, it should be entirely safe to power off the machine in any reasonable way. While pulling the plug seems unnecessary, an ACPI power-off (by holding the power button) should be fine.

As a side note, if the system were booted to such a point that disk writes were a possibility, but login (or display-manager shutdown) wasn't, my first instinct (though probably not the best answer) would be a Magic SysRq sequence, probably REISUO, with appropriate multi-second pauses between commands.

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